How do I change the granny gear on a cheap Walmart mountain bike? I have a cheap ($100) 26" Walmart mountain bike (Hyper Summit) that has a triple chainring (24,34,42).  It appears there is no easy way to remove the granny gear since it has what looks like some type of rivets.  However, the BCD (Bolt Circle Diameter) appears to be 58mm which is a standard size.  I would like to go with a 20 granny chainring cuz I like to ride thru tall grass and need a lower gear.  My rear gears are a 7 speed freewheel with a 28 as the largest cog so currently, 24/28 is my lowest gear which is about 22 gear inches (26" tires).  I will eventually be changing to a 34 largest rear cog (Shimano MegaRange 7 speed freewheel) but I also want the change the front granny chainring for a double gear reduction which I know I will like.  So any ideas how to get the granny gear off?  It connects in 5 places (starfish pattern).  My goal for my lowest gear is 20/34 which will give me about 15 gear inches.

I was thinking if I can somehow get those rivets out without damaging anything critical, I can probably use some washers and chainring bolts to handle any difference in hole sizes.  It seems like it can work with just some light machining.  Once the chainring is off I can have a bike mechanic work on it.  There is always a brute force method too.  For example, cutting the teeth off of the 24 chainring and attaching the 20 chainring to it.  However I prefer trying to bust out the rivets first as the BCD of 58mm matches up with available 20T chainrings.

UPDATE: I am moving forward on this project so will update when I get some actual results.  It might take a month or so to get the parts and schedule a bike shop appointment.  I think at minimum I should be able to get the different freewheel gearset installed but not sure about the 4 tooth smaller granny gear.  If I can get both it should be awesome cuz that will then be a low gear with 15 gear inches which is very low.

Depends on your budget, your requirements, and your mechanical aptitude.  Plus how far down the slippery slope of knock-on upgrades you want to do on a BSO bike.

Since the crank is riveted together, its unlikely to accept any bolt-on replacement chainrings.  Though its possible the makers used rivets instead of bolts but used normal bolt chainrings.  You'll want to pop the chainrings off and have a close look.  It may be possible to buy a MTB triple chainring like what you want, but it won't be walmart-grade or price.

Second problem is Front Deraileur capacity.  Most front mechanisms have a maximum tooth difference that they can swing, and for your existing FD is already coping with a difference of 18 teeth.  A difference of 22 teeth might be too much for it.  Hard to know.

Finances comes into this as well - remember a walmart bike is at the bottom of the quality scale.  I see little point in throwing good money at a crappy bike, when you can save up and get something better.  Don't discount used bikes either - a 5-10 year old used bike could cost as much as a new chainring triple crankset, but have a lot better quality components.

You say you want to ride through long grass - can you expand on why this needs such a crawler gear ratio?  I can ride (very slowly) up a 25% grade on a 26/24, and a 20/34 would be quite a low gearing.

You'll have better luck with the rear cassette upgrade.  I upgraded my 7 speed MTB from a maximum 28tooth to a 34 tooth megarange and it worked perfectly.  All you need is a long rear deraileur, and many bikes already have them because they fit the "look" even if the bike doesn't need them.  This will also decrease the tension on your chain - as the front chainring gets smaller chain tension increases.

TBH don't discount the value of an engine upgrade - ride your bike further for endurance or harder for increasing power.  This helps immensely, as does weight reduction of you and your load.


How can I keep improving after my first 30km ride? I'm a 17 year old girl. I started riding in November, and I don't know how to keep improving—I'm a bit lost. So I will describe my journey up until now and maybe you can help me.
One day my friend invited me to ride to a park. It was 10km, and it was awful. After not even 3km, I wanted to throw away the bike and grab an Uber. When I got home, my dad explained me that I had flat tires, so I guess it was a combination of being extremely unfit and that my bike was not in proper condition.
After that, I kept doing 4km (at about 17 km per hour) 5 times a week. Those rides were tiring but not impossible. Eventually they crept up to 8km (by accident: I would ride while shopping). Then I got interested in trying that 10km to the park again. I did it with my dad, and it was surprisingly easy. (We were going about 15km per hour.)
So I started doing 10km, but on a route without cars, so I could see how fast I could go and if I could maintain the speed. I did that during all December (at about 18 km per hour). It felt great. Sometimes I ran out of breath, but I could maintain it. (I also have chronic sinusitis, so I figured that is mainly the problem.) On December 31, I decided to do 20km. I did them in a bit less than an hour. I was tired after, but I did not struggle that much. I was extremely happy after.
Yesterday on January 7th (a week later) my boyfriend asked me to do 30km with him. I agreed because if I could do the 20km going "fast," then I could do more if I kept my energy and went "slow."
Here's the problem: he and his friends are VERY fit. I could keep up for the first maybe 14km, but after a 30 meter hill I was kind of exhausted. Then we slowed down and I completed the trip but very slow. The last 16km took us 1 hour (when I had done 20km in less than an hour before). I'm proud that I could do it, but now I'm a bit sore, and won't recover or be able to ride again for about a week at least. So I think that maybe I wasn't ready to ride that much.
What do you think? What should I do now? I don't know how much and how often I should ride between 10km and 30km to reach my goal: riding the 30km faster on a stable speed.
Also, here's a picture of my bike. It's a Halley classic 4x4 and has 18 speeds. It's very cheap, and comparing it to my friend's (that are much more professional mountain bikes) it feels like crap. But I wanted to be more fit before buying one.

You've got off to a great start, well done. Several answers tell you how to improve quickly, and they're not wrong. But you'll see plenty of improvement just by riding often, occasionally pushing yourself, and resting when you feel the need after a hard effort.
Riding daily to work/school/college if reasonable, with something for fun some weekends is hugely beneficial. It's how I got started, and now I do rides of hundreds of km, having never used a training program. Especially if it's winter where you are, don't feel guilty about not riding if the weather is bad. In the long run enjoying the ride is a good thing, while making yourself suffer is likely to put you off - the time for that may come in the future if you start thinking about specific goals of speed, distance, etc.


Safety - Improve braking power in wet conditions I have a Dawes Giro Competition with Vuelta Stylus Corsa rims (aluminium I think although I'm not certain), Mavic Aksion 700x25c slick tyres and Tektro R540 brakes. Brake pads are standard Tektro pads with plenty of pad left. All cabling is serviced and fully functional. Braking power is excellent in dry conditions.

When the road is wet, braking power is minimal. I need to improve braking power for the winter for my own safety. I've done some research to come up with some options:

Buy wet weather brake pads (Koolstop Dura 2 or Swissstop Green).
Buy winter tyres with lots of thread to improve grip on road.
Attempt to roughen the surface of the rims with sandpaper.

Option 1 is the cheapest and reviews of these brake pads are very positive. Option 2 is expensive and may not improve braking performance. Option 3 is hit-and-miss and I don't want to damage the rims.

What is my best option to improve my braking power in wet conditions?

Additional information from OP, provided in a comment:
I can apply the brakes quite hard without skidding. I mainly use the back brake. Perhaps new brake pads are my best option.

You have commented

  I mainly use the back brake.

I therefore propose option 4: improve your braking technique before spending any money.

If you only use half of your bicycle's brakes, you can't expect to stop quickly. Further, you're using much less than half your available braking force, because the back brake is much less effective than the front one. This is because, as you brake, your weight shifts forwards, pushing your front wheel harder onto the ground and reducing your weight on the back wheel.  On a dry road, your front brake can do almost all the work of stopping you, and stop you much faster than your rear brake. On a wet road, you need to make more careful use of both brakes because of the decreased grip of your tyres but, still, you need to be using the front brake much more than you do.

Sheldon Brown, as always, has lots of advice on braking.  Many people worry that using the front brake will cause you to go over the handlebars. It is true that if you screw up really badly and front-brake really, very, a lot, much too hard, you might go over the handlebars. I have never come close to doing this. In fifteen years of commuting by bike in two of the UK's biggest cycling cities, I've never seen anybody else do it, either. It's an incredibly rare thing to happen and not something you should be afraid of.

The main difference from rear-wheel braking is that you can essentially pull the rear brake as hard as you like and the worst that can happen is that your rear wheel will skid, which you can stop by letting go of the brakes for a moment. To use the front brake, you do need to learn how hard you can pull it in different situations. As with everything about riding bikes, the way to learn is to practise on a quiet road. I categorically promise to you that, if you brake gently with the front brake, you will not go over the handlebars. You can then experiment by braking a bit harder and moving a bit faster. You'll find that you can brake pretty hard without coming even close to having something bad happen. Brace your arms against the handlebars, too, so you're not lungeing forwards faster than the bike as you stop.

A couple of other things to bear in mind when braking in the wet.

Manhole covers and painted lines in the road can be extremely slippery: avoid them where possible. This is particularly important when using the front brake because front-wheel skids are harder to recover from; it's also important while cornering.
In general, even in the dry, be wary of using the front brake while cornering since a skid is more likely when you're putting load on the tyre by cornering and braking at the same time.
If you see that you might need to brake soon, gently apply the brakes to remove some of the water from the wheel rims. Then, if you do need to brake, your brakes will be more effective.


How do people store bicycles in London? I just moved to London. They seem to have a decent bike culture but I just spoke with a letting agent about renting apartments and she said that most apartments don't allow bicycles inside and most streets don't allow bicycles chained outside. What do I do?! Or, to better fit the general nature of this site, what do people in London generally do with their bikes?

Only people who have private gardens ride bikes.
Bring the bike inside anyway. Maybe get a folding bike.
The letting agent is lying. There are definitely some flats that allow bikes.
None of the above.

To add to Michael's comment if it's your property you can't be forbid to bring a bicycle into your apartment, unless it's somehow unlawful to be in possession of said bicycle. Would you be forbid to bring a crank set or a pair of wheels or a bar set into your apartment? Why would you be forbid to bring those things assembled in a certain way into your apartment?

Read your lease very carefully, or get a lawyer and ask him or her about your situation considering your lease. If you can meet the building owner or property manager and ask, indirectly, about bicycles, do so and get a feel for their attitude about it. If you can tell they are going to be giving you a hard time about it don't even bother, look elsewhere. Having a bad landlord and/or building owner is a whole other problem in and of itself.


Downtube shifters won't stay in low gear on rear derailleur I've finished a bike restoration today and it's my first time using downtube shifters. They work and will span the full range of gears but won't stay in the big cog on the back for long, the shifter itself gets pulled down by the cable tension, I've tried loosening the cable but I'm just not sure how to set it up. Which gear should the bike be in, what position should the shifter be in and how tight do I pull the cable? I've tried tightening the actual shifter against the frame, that didn't help. It was a little D ring that pulls out, it's pretty stubborn so I grabbed it with pliers and managed to bend it off, ghetto repaired for now. I'm assuming it's cable tension.

The H and L screws are ok, I'll try disassembling it if I can find a diagram for my shifter.

Downtube shifters are usually called "friction shifters" and friction is key when fixing the issue you describe. I own and periodically use an old Cannondale with such system. Every now and then I find myself with the same problem as yours. How to fix it? Easy, just tighten the lever of the shifter.

Mine came with an integrated metal triangle handle (couldn't find its exact name, but I've attached a picture as an example.) So they can be tightened using your bare fingers and on the fly, but some other models might need to use a screwdriver. The H and L limits of the derailleurs will have nothing to do with this problem.


Wheel Tire Height Change: 27Plus to 29 All,

I have a 2017 Scott Spark 720. It has 27.5 Plus Tires on it 2.8 maxis recon which I run at 16/18 psi (amazing traction).

I have been getting a lot of pedal strikes (In rocky/rooted turns, mild but annoying and throwing me off line) and have been considering purchasing a 29 inch wheel set to put 2.6 tires on it. I estimate that I would be running closer to 25 psi in them.

Approximately, how much would this increase my BB height by? I think if I could get 1-3 cm increase the pedal strikes would pretty much disappear.

The difference between 622mm rims on 29” wheels and 584mm on 27.5” wheels is only 19mm - about 3/4 if an inch. If you run a narrower tire the rim plus tire diameter different is even less.

In general bike frames do not have clearance for larger wheels so this may not even be possible.

Note that larger wheels will also change your steering geometry.


Are Ultegra brifters compatible with 10-speed XT Dyna-Sys derailleurs? Possible Duplicate:
  Road Shifters, Mountain Rear Derailleur?

I'm looking to build a hardtail mountain bike with drop bars for commuting, touring and some occasional light off-road adventures.

Are 10-speed Shimano brifters like the Ultegra ST-6600 compatible with the 10-speed Dyna-Sys XT derailleurs?

Thanks.

In a word, no. Different cable pull ratio on both systems. You can check out this question if you want a slightly more verbose answer.


Chainring and cassette compatible? I've got a 20 year old Cannondale mountainbike (model # scratched off long ago). It's been used as a daily commuter for a few years and for a couple long trips. I've been told that the original chainring and cassette need to be replaced but I don't know anything about sizing and compatibility. How do I go about choosing replacement parts?

Assuming Shimano components.... You shouldn't have any difficulty with compatibility.  However, as noted above, you need to find out if you have a cassette/freehub or a freewheel.
At 20 years old I imagine you're looking at a freehub...
And likely 7 speeds.   If you want to go to a more-modern 8-speed cassette, the spacing should be the same but you'd need new shifters.
The crank may or may not have replaceable chainrings, and if it does they may not be easy to find.  Nashbar used to sell a wide variety of chainring sizes and bolt-patterns, but current catalogues do not show these.
Likely available from outlets like Loose Screws.
Note that some cranks may appear to have replaceable chainrings but they are in fact permanently attached and you have to replace the whole crank.


Why can't I adjust my Shimano Nexus 8 gear? I have an three year old Electra Townie 8i with the Shimano Nexus Inter 8 hub gear that needs to be adjusted. I followed the guide in this clip

             and it was easy enough. However, the adjustment doesn't "stick".

The problem is that the markers used for the adjustment don't remain aligned after I change gear, and the misfit isn't constant. I get different misalignment if I go 5 → 4 (4 is the gear that should be used when adjusting) compared to if I go 3 → 4. And the problems are even bigger if I go 1 → 4 or 8 → 4.

It is like it slips every time I shift gears.

What's wrong and how do I fix it?

Edit: Forgot to mention. I recently shorted the chain by removing some links since it had stretched itself. Don't know if that has anything to do with this issue.

Edit 2: When I, last autumn, put away the bike for the winter the gear was fine. This problem arose when the bike was indoors (room temperature) and unused.

Having shortened the chain because of stretch is an eyebrow-raising concept because by the time a full link's worth of slack has developed, that would be an off-the-charts amount of wear. But drivetrain wear probably isn't your problem either way. Also there are other reasons to find the need to remove links, like tuning the position of the axle in the dropouts. It's conceivable to need to remove a link to tension the chain if it started out almost all the way back in the dropouts, but that would still indicate a ton of wear in almost any case.

That the error isn't constant in and of itself isn't necessarily an issue because the cable pull of Nexus 8 shifters isn't constant between clicks either.

If in those 3 years this bike has seen some solid use, it's possible it could be due for a basic internal service with a Nexus/Alfine oil "dunk." There are many questions here about this and whether to DIY it or bring it in. Friction and under-lubrication of the internal parts can cause some issues like you describe. Even if it doesn't solve the problem, it's still maintenance the hub needs. If the mileage is fairly low, like under 1000mi/1600km, this is likely not the problem.

Cable housing friction can also cause what you describe. A quick test is whether the adjustment indicator shows the same alignment after shifting into a given gear from either direction. If it doesn't, friction in the housing is likely causing binding in the cable release direction. This is also a problem that wouldn't be surprising on a bike that's seem some use. Lubrication may help, or you may need a new cable and housing. Another basic test for this is undoing the cable release at the cassette joint so you can manually slide the cable through the housing with your hands. It should be pretty smooth.

If it's not either of those two things, damage to the hub internals becomes the next likely possibility.


When installing a rear rack, should I attach the struts to the frame or the seat post on my small bike? For context, the bike is a small Giant Liv Alight and the rack is a Transit Rear Rack which carries up to 40 lbs.

The distance between the mounting eyelets on the rack and the ones in the frame is about 8," while the rack-to-seat post distance is a little less.  There are struts (attachment arms) for sale which are 11".

I plan to carry close to the 40 lb maximum.  Considering the weight, would you recommend mounting the rack to the frame or the seat post?  (As a city hybrid, this set up is a downgrade from the stronger, heavier set up on my touring bike.)

From rack strength perspective it doesn't make much difference. Most of the weight is going straight down to the rear dropout. The front connection is mostly for stability and isn't bearing much weight.

From the seatpost's perspective, it's already carrying 150+ pounds (75kg+) of the rider. Another few pounds is nothing. (Note that racks that cantilever off the seatpost are another issue and they can put undesirable lateral force on the seatpost).

The only problem in attaching it to your seatpost means that it'll be harder to adjust your seatpost. One benefit though is that means it's a tad bit harder to steal your seat.


Is this regular chain/pulley noise or is there someting I should check/adjust? Extra images

I'm 99% certain the noise is coming off one or both of the derailleur pulleys, but not sure if it's to be expected or if it's irregular and something that should be fixed?

Edit

Just remembered - I tried removing the back wheel (including the cassette, obviously) and the noise persisted, so it's 100% certain coming from the pulleys. I just can't determine why, but I wouldn't be suprised if that's how it's supposed to sound.

The drive-train is a bit noisier than it should be.

The noise is not being caused by derailleur indexing being off though.

Chain seems clean, is it lubricated properly?

Things to check are chain and cassette wear. Also check that the derailleur jockey  wheels are running freely.


Do forged alloy crank arms suffer from age-related fatigue? Alloy does have not have a fatigue limit. Does that mean that forged alloy crank arms have a theoretical end of life? Should I worry about 40 year old crank arms?
Could someone with a little knowledge in metallurgy shine some light on this issue?

Aluminum has no fatigue limit and thus it is impossible to make an aluminum bike part that won't fail with enough use.
Fatigue accumulates with load, not time.
Good forged cranks with designs that avoid stress risers in the spider area tend to be pretty good at resisting fatigue failures more or less indefinitely in practice. Weight weenie designs and bad spider transitions do cause exceptions to this. Some riders are also just plain good at breaking cranks, i.e. by being strong and favoring a low cadence.
Heavily used 40 year old aluminum do cause you to make a decision about the risk. If they're lightly used, there is no cause for concern.


How does paraffin chain wax perform in winter conditions (snow, road salt, -20° C)? I’m interested I switching to paraffin chain wax or a wax product like Molten Speed Wax. But I’ve got concerns about how it might perform in winter where I live in Calgary, Alberta.

It’s supposed to be good for not picking up grime so I’m presuming it will do well to keep from picking up salt and snow, but I do wonder if it won’t just lock up or flake off when the temperatures get too cold.

Any insight or experience using chain wax in winter climates would be appreciated.

(To be clear, I’m asking about the kind of product you melt in a slow cooker and immerse your chain in after stripping other lubes off with mineral spirits. I’m not asking about wax based dry lubes that you apply to the chain while it’s still on the bike.)

I posed this question directly to the people at Molten Speed Wax and got this reply:

Our product works great in winter, the key is to put the chain on the bike inside and run it through the gears when the chain is still warm from the pot. The reason is a newly waxed chain is very stiff in super cold temps., but if you pre-break in the chain before going outside it eliminates the problem. This is a tip we give to fat bikers who race in temps.well below zero F.
Concerning salt and sand, that's really tough on any lube. The fix is to have a backup chain or two so if you ride in wet conditions for some time you can quickly change out a chain with a fresh waxed one. Short rides in the wet are no problem but when in doubt re-wax. We ride outside year round and Minnesota is notorious for sand and salt, but wax performs really well.
One last note, don't worry about wax flaking off. Some excess will flake off but all you need is a very thin layer on the chain and that will stay on the chain, particularly on the inside, where all the friction is.
In sum, ride wax year round, no problem.

Obviously they’re promoting their own product so I’ll take their advice with a grain of road salt, but I think I’m convinced to try it and report back.


Straight or Drop handlebars? Can someone explain to me the pros/cons of drop or straight? I've never used drops before and have never owned a good road bike (just cheap mountain bikes) - I am buying a decent single speed soon and unsure if I am better to go with straight or drop bars.

I am not an experienced cyclist and the bike will be used for fun/commute mainly (no on-road riding where I am weaving between cars or anything, cycleways)

Drop bars

The main advantage of drop bars is that you have a variety of positions for your hands, giving you options to make you more aerodynamic or just have a change if you get a bit sore in one spot. Additionally, having your hands 'pointing forward' is a more neutral position for your shoulders, where flat bars cause them to rotate outwards.

Related questions:

What are the positions on drop bars called?
How to use drop bars properly?

Flat bars

The main advantage of flat bars is that you are always in the optimal position to grab the brakes and gears. Additionally, flat bars can be wider, providing more control.

Other bar types

Different kinds of Handlebars


What happened to 69ers? For a year or two, I remember there being a pretty big buzz around 29" front wheel, 26" rear wheel mountain bikes.  They seem to have fallen off the face of the earth.  What happened?

At the time that 69ers came along, 29ers were still struggling to gain mainstream acceptance and 69ers simply didn't offer enough benefit, if any, to really interest the masses. I always felt that 69ers, especially hardtails, did more to combine the disadvantages of each platform rather than the advantages and so did many others. There just wasn't a compelling reason to mess with such a niche bike at a time when you could count all the 29er suspension forks and tires combined with just your fingers.
Ultimately as we all know, 29ers did gain mainstream acceptance, and when there was room for a "middle ground" platform 650b's filled the gap. It doesn't mean the configuration wont come back- I think it still offers potential benefit in a full suspension configuration, but the first wave of 69ers was not a success. At the time it was an untested platform based on an untested platform that typically cost more than all the other comparable bikes due to the small production runs.


Square taper spindle won't fit into the bottom bracket I'm making a road bike with random components I have in my garage.
Everything works ok except for the bottom bracket which is a square taper 115mm long and it is still spinning free even if I turn the adjustable cup all the way in.
Whats wrong? Do the spindles have different diameters?

Since you are fitting Italian cups I assume the bottom bracket shell is 70mm wide according to Italian standard - see Sheldon Brown's Threaded Bicycle Bottom Bracket Crib Sheet.
This shell accepts the spindles with race distance of 55mm - see Bottom Bracket Size Database, section Accuracy of the Sheldon Brown's page again.

As you mentioned you are using random parts so there is a chance that the spindle is made for British ISO where the bottom bracket shell is 68mm wide and the distance between the spindle races is 52mm. This would explain why you cannot set the correct play in the BB bearings.

If I may suggest a solution - I'd use a bottom bracket package with cartridge bearings - for about €20 you get a maintenance-free setup and you get rid of the bearing preload setting problem. I don't know your location but in my case I'd source the parts here (no affiliation whatsoever).

EDIT: Measuring the spindle width.

Choosing the correct spindle width if you don't know the exact parameters of your parts is often a trial-and-error process. You can get some approximate measurements to start with in the following way:

Have a look at the picture attached. Measure the current spindle width (the distance between the ends of the square tapers).

Mount the cranks (blue) to they come in the same direction and measure the inner distance between them (measurement A). Mark the place on the chainstays (green) where the cranks could engage them and measure the outside distance (measurement B).

The rule of thumb (what worked for me) is that A must be greater than B by about 6 mm (3 mm on each side) to prevent the cranks from hitting the frame should any of those flex.

Now, knowing your A, B and the current spindle width figure out what your minimum spindle width should be. Most likely you need a wider spindle than you now have.

Then, insert your spindle into your bottom bracket (with the bearing), mount the crankset and push the spindle to the drive side like it was tightened. Check whether the chainrings do not hit the chainstay and whether they would not be hitting it if the spindle was of the correct width (remove the chainrings and replace them with the cardboard mock-up if they currently do). Also check whether the middle chainring allows for a straight chainline with the cassette's middle sprocket. Or check the distance against the middle of the seat tube. I can't recall the typical road bike distance at the moment but you can search the internet for it.

Remember that the spindles are not symmetrical - the side with greater distance from the bearing race goes on the drive side.


What is the cause of earlier rear wheel lock-ups in the wet? I have faith in Sheldon and Jobst's arguments about hydroplaning.

I do not understand the action of a wheel locking up (entering a skid), other than the intuitive level of braking ~> locks up / doesn't lock up.

I do not understand why the rear locks up more readily on wet asphalt.

Today my rear wheel locked up much more readily, and surprisingly sooner than I would have expected—given that I expected early locking up behaviour.

Why does the rear wheel more readily lock-up on wet asphalt than on dry asphalt.

I've already read this answer: What is the recommended type of tire for riding on wet pavement?

I'm running 47-559 marathon pluses, the bike & load is 20kg ish, I'm 110kg ish.

The ideal answer would give both the science, and render it in a form that a humanities cyclist like myself can comprehend even if by analogy.

When pavement is wet (or icy, or loose, etc) it has a lower coefficient of friction.  Which means that less force is necessary to break from static state (tire gripping the pavement) to a sliding state (tire locked up and sliding).  Braking forces rely on static friction, or the grip the tire has on the pavement.  It may seem contrary, but while you are riding your tire surface enjoys a static relationship with the ground.  The surface of your tire rolls, but each individual patch of tire touches the ground and remains in contact with it (your contact patch) as the tire rotates around.  When you brake with a lower coefficient of static friction and generate enough force, you overcome that static frictional force and move to a sliding frictional force (your tire slips).


What could cause the bicycle chain to break? I'm on an old Muji 3-speed commuter bicycle which uses an internal Shimano gear hub, and I recently (3 months ago) got my bike chain changed by my LBS.

For about 2 weeks I felt the chain would "catch", the way it feels when you're trying to change gears on a bike with derailleurs, and last night on my way home, the chain broke. Is this because the chain didn't fit well?

3-speed drive trains should naturally have a straight chain line and lots of room for the chain, which is typically wider. So I doubt that the chain is too wide.

I suspect the LBS did not correctly insert the chain pin, when reassembling.   If this was the case the pin could be protrude on one side and potentially catch on various drivetrain components.  Continually catching will stress the chain. If the protrusion is significant enough to catch, on the opposite side of the protrusion the pin may not be sufficiently inserted into the outer link plate. Eventually the catching could cause the partially inserted pin to pop out of place, breaking the chain, leaving you stranded. Check where the chain broke to see if the pin at the break point is reasonably flush to the outer link plate or protruding by a large amount on the side where the pin is still in place.

Speculation Warning

This is of course rampant speculation, as I have no pictures to go off of, but is the only logical mechanism that comes to mind.  (And it is something I have actually done and can verify can happen!)


SRAM X01 Eagle 12s RD adjustment to work with 11s cassette + shifter? I want to buy:

X01 eagle 12s rear derailleur
Garbaruk 11s 10-50 cassette

I have:

GX 11 speed gripshift
KMC 11 speed chain

How do you adjust the 12s rear derailleur to the shifter and cassette? Does it automatically adjust, and you just set the high and low limits where they need to be for each cog, and the shifter just moves 11 steps in between, or is there any trick to it?

There are two things that must be correct to move the derailleur  the right distance for each shift.

Cable length pulled per shift
Derailleur actuation ratio - ratio of lateral cage movement to cable length pulled.

The 11 speed shifter will pull the correct amount of cable for the 11 speed cassette sprocket spacing through a matching 11 speed derailleur.  If the 12 speed derailleur has a different actuation ratio the cage will not move the correct distance. There is no adjustment for this.
The X01 Eagle uses what SRAM calls ‘x-actuation’ ratio, GX seems to use x-actuation and ‘exact actuation’ ratios for different components. The Exact actuation ratio is a little different and not compatible.
Check which exact model I’d grip shifters you have on the SRAM site. If they use x-actuation your proposed setup will work. If they use exact-actuation the setup will not work.


Can a tandem's front bottom bracket fail catastrophically? Many tandems have a front bottom bracket that looks like this:

The front bottom bracket is mounted off-centre in an aluminum shell called "the eccentric."  When the pinch bolts shown in the picture are loosened, the eccentric can rotate within the bottom bracket shell to tighten or loosen the tandem's timing chain (that joins the front and rear cranks).

If the pinch bolts broke, or if the braze-ons they fit into sheered off, would the bottom bracket shell pop open?  It seems to me that the integrity of the bottom bracket shell is totally dependent on the bolts; that you'd bend the frame quite badly if they broke.

First off, in order for there to be any sort of a "crisis", both bolts would have to fail, an unlikely possibility on a reasonably well-maintained bike.

But, beyond that, the integrity of the frame doesn't depend on the BB shell resisting twisting loads.  Rather, due to the "truss" nature of the standard bike frame (tandem or not), the load on the shell is almost totally "radial" -- force into or away from the shell.  While this force would tend to "pry" the shell open, it's very unlikely to be substantial enough to cause catastrophic failure.


How can I tell a bike is safe after a crash? I was recently in an accident where a car pulled out on me. I hit the car around the front wheel and me and the bike went over the bonnet and landed on the road, the other side of the car. I was travelling around 20mph.

The bike is in one piece but I'm super-wary of it.

Several people have suggested getting the fork and frame X-rayed to check for fractures. How exact is this science? How certain can you be that the frame is road-worthy?

The bike has an Aluminium frame with a carbon fork and Alloy wheels.

The easy way would be to get a qualified bike mechanic to take a look at your bike for less noticeable problems.

It's not safe to ride a bike if the frame has been noticeably disfigured.
Re-adjust the wheel to be aligned to the handlebars. The wheel tends to twist after crashes.
Go through the final safety inspection you would normally go through, check the tyres, brakes. Replace the brake cables if they are frayed.


Will any Avid brake bleed kit work with my Promax brakes? I need to replenish the fluid in my front brake on my Whyte Portobello (Promax Hornet disk brake) after all of the fluid leaked out through my own mistake.

I'm looking at kits like this on eBay, will it will be fully compatible with my Promax calipers etc?

The only specific piece that you need to worry about is the threaded hose fitting that screws the tube from the syringe into the reservior port, everything else is identical.

Unfortunately I believe that the Promax Hornet use two different types of threads for their reservoir ports on the lever and caliper whereas Avid only use a single type (if someone can confirm otherwise, you are good to go). So you may only have one fitting that works instead of the required two.

There are many generic sets that come with multiple fittings that are cheaper than the Avid kit and will have the fitting you need. They don't ususally come with DOT 4/5.1 but you can buy this at any automotive store.


Hydraulic disk brake stops working when hot; back to normal after cooling - is this expected? I have experienced a strange failure of my brake.

I was descending a steep smooth road, using only my front brake (my rear brake was broken; it was an unplanned bail from a route). I tried keeping the speed low, so i could jump off the bike at any moment.

After going this way for maybe 2 minutes, I stopped briefly to let some car pass (so released the brake for a few seconds). As I continued to descend, I pressed the brake, and surprisingly, its handle went all the way to the handlebar without doing any braking! So I immediately jumped off.

I didn't believe at first the bad luck I had, but then I pressed again and again on the brake (not while riding now), and gradually it returned to normal; after 1 minute it would give full braking force again.

So I wonder, is this an expected way a brake would fail while overheating? I heard that it would start to stink really bad before it became dangerous to ride, so I didn't worry about overheating.

The model of my brake is Hayes Nine.

The least you need to do is bleed the brakes to remove trapped air. It's best though if you completelly change the fluids and bleed. You can do that in an LBS, or yourself if you have a bleeding kit and know how to do it.

The reason for the behavior you described is that air is trapped in the system and makes things mushy and unpredictable. The fact that after a couple of lever presses it came back to "normal" is because hydraulic brakes are auto adjusting both on the pads end (when pads are worn) and on the lever end (when air is in the system).

Air bubbles exist in the system either because a proper bleed was not done in the first place or because the fluids absorbed moisture which vapourated and turned into air as soon as you overheated the fluids. Also note that as soon as the fluids absorb moisture (water) then the boiling point falls even more so having this issue is even easier.


Moaning Disc Brakes? My Disc brakes have been shuddering all day (been riding most the day). And when I say moan, I mean like I can feel the bike shudder up to my rear end. I tried the trick where you rub mud on them and brake hard a few times, and that made them stop shuddering, temporarily. I think the reason they are shuddering is because I recently took out the pads and cleaned them. I also cleaned off the rotors with some simple green. I'm not sure I bedded the pads in right, because I've never really done so before. To bed them in I just braked hard a handful of times after re-inserting all 4 of my cleaned pads. The pads are in good condition, as they have those little gold sparkles. I checked the calipers, and everything looks good. I don't think they're contaminated, as the rotor is clean.

Update: So here's what I've done: scrubbed the pads off with an unused toothbrush, cleaned off the rotors with isopropyl alcohol, and bedded in the pads properly this time (dousing the rotors with cold clean water each time!). Yet it still moaned. The reason I say that past tense is that in adjusting the worlds most nonadjustable mountain bike somehow the brake cable has gone completely slack. I can't even tighten or loosen it on my bike (diamondback overdrive sport). I tried adjusting the calipers, nope. To adjust them, one has to loosen them to the point where they just wobble around or have them so tight that the pads rub the rotor. So yeah, I'm probably going to have to take an expensive trip to the bike shop.

Sounds like dirty pads to me, but disks can be a pain to de-squeak.

The things I'd check are...

Clean the rotors with alcohol, brake cleaner or a bottle of ethanol from the chemist.
Remove and reinsert wheels. Make sure the QRs are nice and tight, and the wheels are straight/centred properly.
Check all the bolts holding your callipers to the frame/fork are tight enough.
Rotor bolts too.
Try and bed the pads in again, 10-20 hard stops should do it.

That should do it really, if it doesn't try new pads on clean rotors. Bed them well.

You could also try lightly greasing the back of the pad where it touches the piston and sanding the pads down, cleaning the rotors, and bedding in again.


TRP Hy/Rd callipers rubbing I’ve just installed a set of TRP HY/RD brakes and I can’t seem to stop the front ones from rubbing the rotor. I’ve tried realigning the calliper but it seems to be rubbing on both sides not just one. I’ve checked the lock knob and it will thread into the actuator arm and I believe the arm is fully retracting. How do I get the pads a little wider whilst fully retracted?

Check that your disc is not warped. Is the disc rubbing the left inboard and outboard pad at different points of the wheel's revolution? If yes, you likely have a warped rotor. Look straight down through the caliper with a bright light and a sheet of white paper held behind it to see when the rotor is hitting the pads.

Is the gap between the pads just tight? The pistons may be extended from the caliper a little. Remove the pads and try pushing the pistons fully back into the caliper.

FYI be aware of advice in this answer about adjusting HYRD calipers.


best rpm for most energy efficiency What rpm when peddling is the most energy efficient aka least calories burned for the fastest speed?

There are a few studies which show that lower pedaling rate is more efficient (i.e. consumes less oxygen/fuel for the same power output):
1, 2, 3
However, it stands to reason that it’s more tiring for your muscles because they have to produce more force/torque to achieve the same power output.
I think your body is pretty good at picking the right cadence for the current circumstances. Most cyclists automatically pedal at around 90rpm when riding at moderate or high intensity. That being said, I think it can still make sense to train at very low or high cadence from time to time. It’s also a good idea to have the right gear range and gear steps for the terrain you are riding.


Is SRAM Apex crankset compatible with 6 speed chain and rear cassette My bike's parts are in need of change and I wanted to do this in stages.

Currently it has shimano parts based on a triple mountian bike front crank and derailleur and six speed rear cassette and derailleur.

First part of the plan is to update the crankset to a SRAM Apex double 50/34 cranks.  So will this crankset be able to use a six speed chain connected to the rear cassette.

As a side I have confirmed with SRAM directly that their road gear is 100 % compatible with their mountian bike gear so my plan is to mix and match the Apex front end with X5 rear end equipement but I can only do this in stages.

Probably not as the Apex crank is designed for 10 speeds, a 6 speed chain will be too wide to fit onto the smaller chainring without jamming on the larger chainring. You would be OK using a 9 speed chain as they are pretty similar to 10 speed chaing in width. So sorry, you will need to up the number of speed front and back at the same time.


Unscrewing a rounded allen bolt I need to take out my rear shock but one of the 2 allen bolts that is holding it (the upper one) has been rounded.

I've been told about various ways that such a bolt can be taken out including:

hammer a torx in and unscrew
drill a line using a dremel and unscrew with a screwdriver (I don't think the latter will work, the bold is too tight)
hammer a larger allen key in and unscrew
drill the hell out of the bolt (I don't want this because I'm afraid I'll damage other parts of the link (bushings etc)

What do you propose for this case?

I'd try a screw remover like these. You'll need to either get a set or bring the bolt in to make sure you get the right size (Sears sells their own version that's supposed to be excellent). The good ones have a left-hand thread and a small cutting head to bite into the bead of the bolt; this looks like a really good candidate for a screw remover since the head is nice and large and has enough material for the remover to be able to grab.


Fixed gear bike chain alignment I have recently converted my old early 90s 18 speed Peugeot road bike to a fixed gear.
The chain is clicking when pedalling and is out of line by about 10mm as you can see in the photo.
The rear cog is a new 18t fixed gear. The chainring on the front is the from the original bike is 52t and was the 3rd gear previously. I have removed the two other chain rings.  The new chain itself is 1/8th inch.
If I get a new square tapered crank set and chain ring is this likely to improve the alignment? Will this bring the chain ring closer to the bike and more in line with the rear cog?

The pic makes it unclear but I assume flopping the ring in to the middle position has been done and not helped.
First you need to decide whether 52-18 is what you want. It probably isn't. Your answer may inform which route is more economical, since buying a new ring will cost some notable percent of what a new crank would cost. Also, figure out whether the 52 will work in the chainline position you need it to. It very well may not.
If you want to make this crank work, measure your rear chainline and your front chainline. If you have a symmetrical BB spindle, multiply the difference by two and buy a new BB with a spindle that much longer. If asymmetrical, take its measurements and do the chainline/spacer math to arrive at the spindle length you need to simultaneously get the front chainline matched to the rear while also centering the cranks. The usual offset is 3mm but it's not universal.
If this a modern off the shelf track hub, if you drop in any modern track crank with its recommended spindle length it will basically work in terms of chainline. Meaningful exceptions to that are rare. As before, what may not work is frame clearance. You will have to get a sense of that up front before making your other decisions. In some cases that will drive gear size choices.
I'm pretty sure this won't have a French shell, but you should corroborate that before buying things.


Brake lever and shifter for bullhorn I have a Sora 3500 set on my bike except for the shifters, which are Alivio ST-M310 and a 22.2mm flat bar.  Now I have a new bullhorn which I would like to install, but the old shifters don't fit, because the diameter of the bullhorn is 23.8mm.

I would like to have the brake and the shifter at the end of the bar, somting like this image. I thought that a bar-end indexed shifter and TT brake lever would fit quite well. I have a 2x8 gear system so, I think a Shimano Ultegra 6480 Triple 8sp Bar End Shifter would be perfect.

But I can't find a TT lever-like brake that has a mounting ring rather than plugging in to the end of the bar.

Is there a brake lever (for caliper brakes) I could look for so that both (brake & shifter) can be mounted at the bar-end?

UPDATE

After some search I found two solutions: one explained well here,
another solution is this, and here the brakes are Reverse Brake Lever.

Where can I found a reverse brake lever with clamp mount, and not internal handlebar wedge-sleeve mount?

I think, I found the answer, but can you correct me if I'm wrong?

The levers in the first post that you linked to appear to be Cane Creek Crosstop (interrupter) levers. Tektro, Paul, and probably others as well, also make levers like this. They usually work by pressing on the cable housing (effectively making it longer), which is split at the lever. It looks like the levers in the photo are being used as conventional levers and are pulling on the cable itself – the cable appears to dead ends in the barrel adjuster of the levers rather than passing through as it would in a conventional interrupter lever setup.


How to service a 1995 Schwinn Phantom Coaster Brake hub? I have a 1995 Schwinn Phantom beach cruiser with a coaster brake that I'd like to service. The coaster brake is staring to feel sloppy and hasn't been looked at in a long time.

What tools will I need?
What are the steps to service it?

Not sure if this is an exact match, but it should get you pretty close:

Park Tools: Coaster Brake Hub Overhaul


Should I avoid sitting on top tube on my carbon bike? In another bicycle discussion forum I encountered a thread about possibility to damage carbon frame by sitting on top tube while stopped.

I see some sense in it, as generally tube walls are a lot thinner in the middle to save weight and are not designed for this kind of load. The problem is, I have not seen any warnings from manufacturers about this habit, nor there are stickers on the frame suggesting to not do it.

So the question is - Is this a real problem, should I change my habits?

UPDATED: There is one local person who does carbon repairs, he claims that he has repaired multiple frames which had been damaged this way.

I have never had or heard of a problem.
Over at www.velominati.com, one of the rules is

Rule #80 // Always be Casually Deliberate.
Waiting for others pre-ride or at the start line pre-race, you must be tranquilo, resting on your top tube thusly. This may be extended to any time one is aboard the bike, but not riding it, such as at stop lights.

While some of what they say is tongue in cheek, this one is not. Most people I know do it, and have done for years.


How does this hub come apart? Really, I have two questions.
But first, I see no place to put a wrench on this hub.
Well, there is one small notch on one side on the dust cap (on the other side).
How do I get this hub apart?  It's wobbly and I want to repack it.

The other problem, of course, is the several metal damage from my cassette.  Once I get it apart, I can see if it's possible to replace that part... we'll see.

Really, I'm just looking for the proper procedure to get this thing apart!

thanks!

Its likely disassembles in one of two ways:

two cone wrenches (one on each side of the hub) to remove the jam nuts. This is the likely option. From your photo it looks like there is a flat spot on the jam nut.
two hex wrenches (one on each side of the hub) that fit into the axle end.

Two videos demonstrating these techniques:

http://aol.it/15nYDub
http://aol.it/Ioc7T2


installing 11-40T Sunrace cassette with Sram Rival 22 I'm trying to build up a hillclimb bike (Mt. Washington) - current set-up is OK, but I could use the help AND don't care about temporarily losing the use of my big chain ring.  Current set-up (all SRAM Rival 22):

50/34 crankset
11-32 cassette
mid-length rear derailleur

Seems like the conversion should be possible with Sunrace CSMX8 cassette (11-40T, 11-speed), the Wolftooth derailleur hanger extension, and a SRAM PC-1130 chain.

Assuming this is possible, are there pitfalls to consider?  Other recommended parts?

RESULTS
For those of you who arrive in this rather obscure location wondering about a similar set-up, I made the change described above and disabled the front derailleur (per @Argenti Apparatus's suggestion) and it worked out beautifully - so far, shifts as well as or better than the standard set-up with the SRAM cassette...

SRAM Rival 22 mid-cage derailleurs work with 11-28 to 11-32 cassettes. Rival 22 cranks come in 52/36,  50/34 and 46/36 so I'm guessing the total capacity is
(32-11) + (50-34) = 37.

If you will be running as pseudo 1x setup by not using the big ring, you will have plenty of capacity in the rear for a 11-40 cassette. Derailleur hanger extensions do apparently work but you may find you have some shifting issues.

Consider disabling the front derailleur, changing to the big ring by mistake could wreck the rear derailleur.


Were the 1970s bikes from Motoconfort the same as those from Motobecane? I've got something called a Le Champion from Motoconfort dated to the 1970s which, aside from the different decals, is indistinguishable to me from Le Champion models from that era from Motobecane (going by the pictures thereof I can find on the Internet)-- however, I am in no way an expert in either old bikes or French bikes; Are Motoconfort bikes just a re-badging of typical Motobecane models from that era, or is there some tangible difference between the two marques? i.e. is a Motoconfort Le Champion from year n exactly the same as a Motobecane Le Champion from year n?

She's such a cutie.

Motoconfort is absolutely not a ripoff or a knockoff from a Motobécane. For some time there was an overlap between the brands until the mid 70s but the factories were the same.

So to tell it shortly, if it's a Motoconfort Le Champion it's exactly the same bike as a Motobécane Le Champion even in terms of factory equipments or frame quality.

She's real as they come, and that's coming from a Motobécane hardcore lover that owns five of them (even the tiny but heavy foldable one).


The Effects of Widening Seat/Chainstays first time so bear with me please.
I recently had to replace my rear wheel. Went to LBS and the only options available are 130mm spaced. I have a nice Specialized 1980s frame that measures 126mm. It's a steel frame so squeezing in the new wheel is no problem. However, I'm curious how this will affect the feel of the bike. By essentially widening the "stance" of the bike, will I lose some responsiveness and agility or will it feel the same? Followed up by how will this affect the tension of the shifter cables that travel along the chainstay? Thanks for your help!

PS. If anyone knows where to find a 6 speed 126mm QR rear hub that I can build a wheel around (or a complete wheel) let me know. I've not had much success searching for one. Thanks again!

Not sure what you mean by 'stance' of the bike, but rear wheel will not be moved relative to the bottom bracket by a perceptible amount. No change in handling will result.

Similarly, shift cable will not be affected, but can be adjusted anyway.


Why did I lose braking power after hitting a curb? Recently I hit a curb on my bike. I heard a cracking sound, my front disk brake (cable) felt stiff, and I could feel a lot of resistance from the front wheel. I left it alone for a few minutes, and when I came back, the brake was back to normal, but I could hear some grinding in the front bearings. I also soon realized that I couldn't stop as quickly as before. Today I took the bearing apart, cleaned it, applied fresh grease and the grinding disappeared. The brakes still were noticeably weaker. I tried smoothing the rotor with sandpaper, but that did not help. What could be the reason?
Additional information:
I was moving at around 25 km/h, the curb was about 3-5 cm
The axle is straight, the dropouts seem to be fine
The cable shroud seems to be a bit deformed, but that deformation does not change how far it can retract
I took the whole caliper apart, sanded the rotor and pads. After reassembling, I think it is a little better, but not as much as it was before. Or that's just placebo, I'm not sure.

Based on the second photo, I'd guess the rotor is no longer parallel to the brake caliper.
Thus instead of having flat contact between the pads and the rotor like
=| |x| |=

you now have smaller area of contact.
=/ |x| /=

Sanding the pads has rounded them off a little, increasing the area of contact a little.

The best fix I can come up with is re-aligning the caliper with the rotor.

Take out the front wheel and fit a slip of paper over the rotor, then reinstall so the paper is in the caliper.
Back off both bolts holding the caliper to the fork, enough so it can slide.
Press and hold the brake lever on the handlebars and help the caliper find its center.
Tighten the two bolts sufficiently (not excessively)
Release the brake lever
Spin the wheel to pop the paper out, and test.  You're looking for no-rubbing and that the pads touch the rotor all-at-once.

Small changes will have a big effect on the brakes.
The problem may be if the little mounts that support the caliper have been bent, or if the caliper's mounting tabs have bent, or if the mounting bolts are bent.
You might need to replace both bolts if they are not straight.
I would not recommend attempting to straighten the caliper if its bent - they will probably break, or if not will be weakened.
If the fork's mount points are bent, you may be able to file/mill/sand the top surfaces to be flat and at right angles again, but it is hard to get perfect.
Upshot - avoid riding your bike into kerbs/curbs.


Is there a front derailer type that can be mounted on a frame without braze on or fitting on the seat tube, or clamping? As the question says, is there a front derailer type that can be mounted without having a fitting or braze on on the seat tube, or without clamping to the seat tube (because it's a weird shape, or made from a material that one cannot safely clamp too)?

To my knowledge there are clamp on derailer that expect a seat tube that is circular in cross section and braze on derailers that expect a brazed on fitting on the seat tube.

Finally there are derailers that are clamped on by the right hand bottom bracket cup/ring, but as far as I can tell they also require an additional fastening method on the seat tube to prevent them from rotating around the bottom bracket.  I think these are sometimes called E-Type or Bottom Bracket derailers.

'E type' is a front derailleur attachment standard. Some frames provide an E type mounting point directly, some require a 'back plate' that provides the mount point that is clamped by the bb cup.

As far as I can tell, some back plates are clamped by the cup and have no other provision to prevent rotation. There is not very much fore or aft force on the derailleur so presumably this is not a problem. Other back plates have an additional hole that matches a threaded hole on the frame, so that an anti-rotation bolt can be fitted.


Protecting Tires from House Cats I have a friend with several cats, one of which destroyed the material of their bike tires and is presumed to enjoy doing so.. having acquired new tires and tubes (but not yet put them on), how can we prevent the cat from chewing/scratching the new pair?
We had thought

bag the tires (no good; likely too thin and they love bags too)
move the bike outside (no, it will definitely be stolen)
spray the tires with lime juice, vinegar, etc. which the cat will find unpleasant (this at least works for ferrets which love chewing cables)
decoy tires (see: cats on keyboards)
some sort of removable, thick rubber coating (perhaps a second, larger pair of tires cut to fit over mounting)
hard case for bike (probably too expensive)

Other details

bike is a Schwinn road bike without fenders
no garage is available and it is impractical to store at my place
the cats are otherwise delightful
bike will be left unattended indoors for long periods of time (weekends/workday..)
open to trading in the bike and getting something heftier if that's the only solution

Likely also suitable for Pets StackExchange, but I doubt this is an unheard-of problem in this community

Have you thought about a bike cover or bicycle wheel covers ?
This seems the most logical form of protection for little outlay, the most effective method would be to move the bike out of reach of the cats but if that’s not possible then a cover of some sort may suffice.

If the cover isn’t suitable or the cats destroy it, you could easily make a bike stand from some 6mm mdf, make it wide enough to stand the bike in but tall enough to cover the wheels
If I was on a PC i would draw up a quick image / diagram of a simple stand.
If you have hydraulic brakes do not stand your bike upside down.


Brake hard on new cycle I saw someone after buying a new bicycle (a hybrid), pulled the brake as hard as he could for few seconds and dragged the cycle along while braking like that, 1 brake per centimeter.

Why did he do this? I didn't had a chance to ask him but did he do this to test something or fix something? Is it usual to do this to new cycles?

Here one more thing I should mention is that the brakes are mechanical disc brakes and before doing this to his cycle, his brake tuning was fine and after doing that, the tuning was not fine at all.

I can't add a comment yet so I provide this as an answer. The guy was bedding or burning-in the brakes. It makes sure the pads are seated and wiped of factory oil, grease, and other contaminants.

Disc brake break-in?

Sounds like he was doing it wrong. Unless the fact that the brakes weren't working after he did it indicates that the process uncovered a problem.


Fitting question for first trekking bike - differences in stack and reach I understand this might be a pointless/dumb question, but as an bike freshman, I am confused:

Trying to select an entry level first bike (cross/hybrid) and so far I'm between two of them (local EU brands)
I'm 176cm, inseam 74cm. For the first one, i fit better on their 18'' model and on the second one on their 19''.

I tried both of them on a LBS but unfortunately not for an extensive ride - just a tour around the block. However, their frame geometry is quite different,  having:
Stack:518,2 mm
Reach:383,5 mm

And  having:
Stack: 497,7 mm
Reach: 394,6 mm

I enjoy upright riding position and I favour stability and comfort more that speed. With these in mind, am I wrong to assume that the first one is a better option for me? Will the difference be too noticeable?

Thanks a lot.

Impossible to tell you whether a couple of centimeters either way will make a bike fit you better. A slightly lower bar may actually suit you better than a higher bar, even though you value comfort over speed. You might feel slightly more stable with a little more weight on the front wheel.

Honestly you just need to ride the bikes back to back and make a decision as to which you feel comfortable with.


Can I change my 7-speed rear derailleur to an 8-speed? I bought a 2013 Cannondale Quick 6 Hybrid for my daily commute almost exactly a year ago, and I'm looking to give it some upgrades. It currently has a 7-speed Shimano Altus derailleur, and I was hoping to replace it with something a bit more "road"-y, like the Shimano Claris.

However, the Shimano Claris is an 8-speed derailleur while both my cassette and shifter are 7-speed. Also, I don't see anything saying if the Claris would work with the rapid-fire shifters (also Shimano) that I have on my bike right now. The chain is certainly 8-speed compatible, but that's about as much as I can be certain of at this point. If I wanted to switch out my derailleur to the 8-speed, what other parts and/or changes would I have to buy or make in order to make it work?

Thanks for all the help in advance!

Rear derailleur's speed markings are generally for marketing purposes - if you're under 10 speed in Shimano, you can swap between road and mountain rear derailleurs without problems provided they have enough capacity for the rear cog combination you're using - the cable pull is the same, so road and mountain shifters can't tell the difference (often in fact, you'll see touring bikes or road bikes with big rear cogs with Shimano Deore derailleurs since the mountain derailleurs can have bigger cogs in the back at the cost of a few grams of extra weight and looking less cool). The speed number you can effectively ignore, since the amount the derailleur moves is determined by the amount the shifters pull the cable (in theory, the cage might be thinner or something, but in practice this doesn't really matter).

You also won't notice a difference in performance or anything if you just stuck a Claris rear derailleur on. It would just be a waste of money.

If you want 8 speeds, you need to buy an 8 speed cassette (Shimano compatible) and an 8 speed Shimano shifter for the rear. You can keep the existing derailleur - you just need to adjust it a bit. You'll need some special tools (cassette remover, cable cable cutter, big crescent wrench) in addition to hex keys in order to do this as well. Swap the shifter and put the cassette on, adjust the derailleur and you've got an 8 speed setup.

Personally, I think you should just stick with 7 speeds as it is sufficient for commuting (the extra speed doesn't really help - its just a bit easier to find 8 speed parts these days, so thats pretty much the only reason to go from 7 to 8). Spend your money on beer or something instead. The Cannondale Quick 6 is a relatively cheap hybrid (~500 dollars new), so if you want something faster, you're probably better off getting a different bike with probably more aggressive gearing and geometry (say a flat bar road bike like the Giant Escape or something if you want to stick with flat bars).


How can I lower the gear ratio on my son's bike? I got a SH Commencal 24" MTB for my son. He loves it - except on climbing steep slopes where he runs out of steam.
It comes with a 7-speed 14-28T freewheel (Shimano MF TZ21) + Acera derailleur, and a single 36 tooth chain ring.
I added a photo in case it helps.
What would you suggest for getting the lowest gear ratio -- lower ?
The cheaper, the better.
I have basic knowledge of bike mechanics (but I'd use this as an opportunity to learn) and basic tools (but then again, there's eBay).
If it's over my head, I'll ask a bike shop to do it for me, but it will add to the price and be less fun.

The specific model of rear derailleur you have is an Acera RD-M360 SGS, produced about 2009-2011, for 7 or 8 speed drivetrains. Shimano very helpfully provides archive specifications on the product info page.
Looking in the 2009 spec PDF we can see that the max size of the largest sprocket the derailleur will handle is 34. I believe 12-34 freewheels do exist, but you might have to hunt around to find one. That would be the cheapest way to lower gear ratios. (I'm guessing the crank on this bike does not have replaceable chainrings.)
Removing and installing freewheels is very straightforward, but requires a special freewheel removal tool to  get the old freewheel off, and there are many different types of tools for different freewheels. See this Park Tool Repair Help video for how to select the correct tool. Other than that you only a large adjustable wrench in addition to basic tools.
A larger range freewheel may require the chain to be a few links longer, which unfortunately means sizing and installing a new one. I installed an 8 speed rear derailleur on my son's single chainring bike recently and used the chain sizing directions for 1x drivetrains in this Shimano manual. This is working fine so far.


Why is a proper road bike pedal preferred for road bikes? I've been riding road bikes for a couple of years, but with mountain bike pedals, I've been thinking about switching over to a road bike pedal, but what's the reason? Is the performance improved or is it more about conform?

Hmm, we're kind of hitting most of the answer but not all of it (in my opinion that is!).

Its probably better to ask this the other way round - why not use a road pedal on a mountain bike...

On a road bike you're generally going to keep your foot in the pedal, you're only going to take it out to stop so therefore you want it to be as simple and as light as possible.

On a MTB you're liable to have your foot on and off more often, you're also likely to want to be able to stomp your foot onto a MTB pedal and have it stay there so it needs to have a larger platform area. You could also make an argument about MTB shoes being softer but the designs tend to be driven by competition and so that's probably more coincidence than anything else. If we're talking about using toeclips then clearly you'll need bigger pedals and clips for MTB boots than road shoes.

And weight does matter - it may only be a few 10s of grams but a few here and a few there will add up and all other things being equal less weight will make a difference.

I use clipless pedals - which I recommend - and I have one pair of shoes that I use on all my bikes, some of the pedals are fairly minimal for road, some clearly MTB, some hybrid but more MTB than not and all work with the same SPD cleat. Paradoxically my current setup has double sided pedals on the "road" bike and single sided on the MTB type pedals on my shopping bike...

So why road pedals? Assuming clipless and further assuming that you will only wear cycling shoes then you don't need the "complexity" (no difference in my pedals) or the weight of a full platform - so why have it? But the real difference will be in the shoes you chose to use.

(As I final thought I actually have two pairs of shoes - one waterproof - and a pair of sandals and they all have the same cleat so that I can use whichever is appropriate to the weather on whichever bike I happen to be out on.)


Can I put the speedometer sensor for my cycle computer on my rear brake line? Pretty simple question I hope. I picked up a Bontrager Trip 3 because I saw it recommended several times for rear mounting (this is on a bike that will sit on a trainer). However, I am finding that there is nowhere on the rear portion of the body that puts the speedometer sensor close enough to the spokes of my wheel for it to sense the magnet as it travels. The only place I've found that might work is on the plastic sheath around the brake line near the rear disk brake. It looks like it requires about 1-3mm distance to be able to pick up the magnet - there's almost nowhere on my bike's body that comes that close to the spokes. The brake line sheath isn't very stable (it's just hard plastic) but it seems to work.

The only other option would be about 1" of shimming near where I have the cadence sensor.

The seatstays and chainstays for the bike are extremely wide because of disk brakes.

I have had a similar problem and solved it by using a small piece of foam pipe insulation. I see no reason why a piece of sponge or similar material wouldn't work. I used two zip ties to hold the spacer in place, then positioned the sensor pick-up.


What is the stem/seatpost thing on the Bicymple? Anybody know if that's a pre-existing part that's been repurposed or if it's something that they've had custom fabricated?

There are more pictures on their kickstarter page.

It's a stem, which has had the bar mount replaced with  a seatpost clamp.  It is a custom part for this frame design, only.  They are having it fabbed.


Sounds like there is stickiness on my tire, but there isn't! I noticed starting yesterday my front tire has been making a strange sound. It sounds like there is a small piece of tar stuck to the front tire and it makes a faint noise of sticking and unsticking from the pavement once per revolution. I inspected the tire by hand, and it is perfectly clean. There is nothing visibly wrong with it whatsoever. It's also not melted. The bike rides perfectly. The tire and tube are both very new. The sound happens whether pedaling or coasting. Sometimes on different road surfaces it disappears, but I'm not sure.

Because the sound only happens when moving at speed with weight on the tire, I can't reproduce it standing still. Unless my ears are broken, it's not coming from anywhere else on the bike. What could this possibly be? Paranoid delusion?

Ken Hiatt mentioned a wet spot between tire and tube, and I'd like to add something that have already caused me the same symptoms: the anti-puncture band.

In general, there is an overlapping zone of anti-puncture where one tip lays over the other. Depending on how they sit against each other, this might cause this noise. In my experience, this is also a cause of puncture, because the edge of the band can "cut" a groove into the rubber and eventually puncture it.

I wouldn't discard, for the sake of completeness, something inside the rim if it is double-walled (sand, nipple, whatever), or perhaps something related to the loading/unloading of some spoke when the bike rolls with your weight over it.

Hope this helps!


NuVinci continuous shifter I'm building a bike for a woman who injured her hands in a fall and who now experiences pain when using trigger shifters. She does a little better with grip-shifters though even their resistance gives her trouble if she has to shift often. Does a NuVinci hub with its continuous/stepless grip-shifter have a mechanism that is easier to twist than a normal grip-shifter?
BTW, is NuVinci still in the human-powered bicycle business? Some links on their web page go to non-existent pages, and they don't have any dealers in my metro area, which has over 6 million people.

The NuVinci system is quite interesting. There is no spring to pull against in the shifting mechanism, the shifter relies on two gear cables. You could reduce the required effort by using the best quality cables and housings available. There is resistance on the shifter though, not dissimilar to a normal grip shifter but without the clicks to power over. Whether it would suit your application very much depends on whether it's easier by a big enough margin to be noticeable.
NuVinci changed their marketing name to enviolo fairly recently. The products are basically the same though. https://www.enviolo.com/en/
Like you might expect, you'll only know for sure once you've tried it. Does anyone in your area use one of these systems?


What is this rubber ring around the top tube for I have seen these on a few bikes. What is the purpose :S

It protects the frame from the handlebars. The handlebars, unrestricted by brake or derailleur cables, can rotate freely to the point that they can smack into the top tube. This is particularly easy to do when carrying the bike.


Tour de France RV/Campervan parking policy Are there any rules regarding parking an RV/Campervan alongside the Tour de France course?  Can you just park anywhere that isn't yet closed off?  How long before the race comes by do you need to get there?  How soon after the race can you leave?  I'm asking specifically about stages in the French Alps.

My research suggests that there is no absolute answer to this.
According to Watching the Tour De France in person

If you're planning on camping out on top of the more popular mountains, try to arrive a good two days prior to the race coming through to get a prime parking and/or camping space.
Road closures
Once you have decided where you would like to see the Tour, check prior to arriving – or with the local tourist office as soon as you arrive – to see which roads are going to be closed (and when).

Spectating Tips For A Grand Tour says

The race website or local newspaper will have the schedule listing when the race will pass. However this is more for information because on a big mountain stage all the roads are blocked from the morning onwards. The roads close well in advance of the race. There’s no fixed time but on a big mountain stage you can expect the route to be closed at breakfast time to cars. It’s why many will drive up the day before and camp overnight, indeed even if you drive up a climb you’ll find many of the parking places are taken days before by camper vans.

Another site (can't find it right now) said that the Gendarmes can close roads or move you on as they see fit.
So, many people want to see it, and there are no guarantees.


Relation formula between fork length change to headtube angle and bottom bracket height As we know, changing the fork length will change bike geometry a bit. For example, increasing fork travel by 10 cm will make the headangle slacker and raise the bottom bracket. I consider to increase fork travel on my bike by 20 mm, and to fix the increase in bb height with some headangle changing headset (like Cane Creek angleset). While I don't mind my bike to be slacker (actualy it's one of the goals of this modification), I do want my BB stay on the same height. Is there any formula we can develop to understand how would a change in fork length influences the headangle, and how the headangle influences the BB height?

This isn't a formula for you so maybe not the answer you're looking for, but it gets tricky because a fork isn't just a straight line; because it has offset it's kind of like a triangle itself for the purpose of doing the exact math here.

The thing most people who care about this question would do in practice is model the frame's fixed points in a 2d CAD program, model the forks in question (remembering that to do so you're making a right triangle where the axle to crown dimension is the hypotenuse, the offset dimension is one leg, and the other leg is an unknown length that can be solved for or figured out automatically in CAD), then plug each fork in to the frame model such that the unknown leg is in line with the head tube, and then pivot the whole thing around the point of the rear axle until the front axle snaps to being in plane with the rear. Then you can see the resultant head angles and BB heights easily. You can also easily see what angle changes at the headset would give you. There are many free 2d CAD programs that can do all this.


How to improve band brake? I have been working on a 26" folding MTB, and its coming together slowly.  The rear wheel has a band brake and for the life of me I can't get it to work well.

I have no experience with this kind of brake.  Nearest I've worked with is a drum brake on a tandem, and drum brakes on a car.

 Band side of brake.  When actuated, the silver lever on the upper left rotates, and the band is pulled up and right.  Since the other end is fixed by the rusty rivet, the band has to take a shorter path and decreases in circumference thereby tightening on the drum.

 This is the drum which is attached to the wheel hub.  It is threadded onto the non-drive side.

So when braking under no-load this brake works perfectly and stops the suspended rear wheel quickly.  When riding, this brake has a barely-perceptible slowing effect, and absolutely nothing if its a downhill grade in any way.

I have tried a light sand of the drum to remove any glaze.  I've also sanded the band lightly but its soft so didn't want to tear it.

Also I've applied an electrical cleaner spray called Contact60  That also made no difference to braking.   The band appears to absorb the spray

So far I have not applied "brakleen" because the band is soft and am worried about it absorbing into the band, rendering it contaminated permanently.

What else can I do to improve this brake?  Or should I simply replace the whole thing with a conventional rim brake ?

In the end I improved this brake's operation manyfold, but its still pretty mediocre.
While working on it, I found the brake pad (strip?) was slick.  So I presume some idiot applied oil to the brake in an attempt to make it quieter.

The main fix was to extract the band, and use a hot air blower (a workshop version of a hairdryer) to warm the band and I could see the oil running out of the band and dripping off.
I used a non-contact IR thermometer to make sure the top of the pad didn't exceed 150 degrees C and kept the hot air moving to not overheat one spot.

After a while the oil stopped dripping, so I had to use a blotting method; I'd heat the brake pad and then quickly wrap it in a couple of paper towels.  The oil was clearly visible wetting the paper.   It helped to massage the brake pad by hand, so I wore some decent leather gloves as heat protection.There were at least a dozen head-blott-massage cycles, and I stopped when the paper towel did not get wet.

On reassembly, the brake was okay when free-spinning in a stand.  There was a lot of fiddling back and forth with the cable tension and the two standoff screws that set the band's resting position, close enough but not so close that it rubs on the drum.
However when the bike is loaded, it absolutely screeches when braking.  This is what makes me think an earlier owner oiled the brake, which certainly quietened it, but at the expense of function.
I did lightly sand/scour the drum and the inside of the brake pad, and it really made little noticeable difference.

A better solution would be as Bruce suggests, and fit a rim brake caliper.  While this frame has a brake bridge, the rim lacks a braking track.  Given this bike is literally a shopper / dunger / beater, I'm loathe to throw more money at it.   However I did replace the fork to get canti mounts, and the front wheel has functional and effective V brakes on it now.


Replacing the largest sprocket in the cassette with a larger one? Got this nice old bicycle as a gift from friends, and it has 7 sprockets in the cassette, plus a hub-gear mechanism with three gears (only two of these work though.)

To come to work I must ride about 7 km, last 2km are uphill, and the last 800m are the steepest. Even with the shifts setup at highest torque, I can manage the entire hill, but only pushing myself to my limits. I would like to have it a little easier.

Would it be a good idea to replace the largest cog in the cassette in this old bicycle with a larger one, so that the toughest uphill parts can become proportionally easier?

Some additional photos:
Bicycle photo album

I was surprised to find that not only did they make this configuration, but it is still made and is available as a 3 speed IGH (integrated gear hub) and a 9 speed free-hub. I have seen older Altus derailleurs similar to the original in the photo used with 28 tooth 7 speed cassettes. I would feel confident in stating that such a set up would work here. A quick search shows a wide range of 7 speed units are readily available. Looking at the photo of the front crank I don't think a smaller tooth front sprocket would be available. The prospect of installing a 3 speed front crank would be a interesting engineering exercise.


Is 7-speed for 10-speed cassette replacement possible? I have a city/touring bike with Shimano MF-TZ21 freewheel hub which is 340mm wide (I measured). I would like to change it to a 10-speed cassette 11-25 or 11-28 but I am not sure if it can fit between my chainstays (129mm). I know I would need to buy shorter hub also (and deraileurs, shifters, chain etc.). In bike service they told me (without measurements) they are not sure if new 10-speed package can fit between my chainstay. I googled 10-speed Shimano cassette dimensions but I could hardly find anything I can interpret correctly.
Please help, can I fit new package in 129mm?

Higher number of speed cassettes and freewheel are not wider, they have smaller sprocket spacing.

If you were talking about a cassette/freehub system, you would be able to fit a 10 speed cassette on the existing hub because the freehub body is the same width for 7 to 10 speed cassettes. (11 speed requires a wider freehub body on road bikes).

I'm not terribly familiar with freewheels, but I would think the same principle holds.

However, if you have a 7 speed rear, freewheel equipped, Tourney level bike, and you want a 10 speed rear, you really want a whole different bike. To get a 10 speed rear you need to upgrade to Tiagra or Deore, depending on if you have a road or mountain style bike. You'll need to replace the crankset as well as the derailleurs and shifters. Buying the bare drivetrain groupset will be expensive, require a lot of time to install, require special tools and will give you a lot of headaches trying to get it set up correctly.

Go the easy route and get an upgraded bike. It will probably be cheaper and you'll get an upgrade on every component, not just the drivetrain and it will work right out of the box.


How do I get a Garmin Cadence Sensor 2 to pair with an iPhone? I have bought a Garmin Cadence Sensor 2. After installing it on the bike and rotating the cranks to wake it up, theoretically I should be able to pair it with my iPhone but it doesn’t appear in Bluetooth Settings. The documentation is abysmal and doesn’t go into any useful detail on the pairing procedure. What’s the trick to get it to show up?
(The iPhone is a 12 Mini running iOS 14.2, but I couldn’t get it to work with my iPhone X on iOS 13 either.)

It seems like it could work using their Garmin Connect App.
See Page 5 below.
https://www8.garmin.com/manuals/webhelp/cadencespeedsensors2/EN-US/Cadence_Speed_Sensors_2_OM_EN-US.pdf
See this snippet too:
https://www8.garmin.com/manuals/webhelp/cadencespeedsensors2/EN-US/GUID-E87E78BB-03DD-48C1-AA67-A69E591B01FC.html
However, I think optimally this thing is designed to be used with a bike computer Garmin Head Unit vs. a phone as I am not sure how it will display the cadence info as you ride. Note I never used my phone as a bike computer so perhaps there is a way to do that.


E-bike battery charger making horrible noises, only works certain outlets? I had posted on endless sphere but since then I have possibly made a little discovery.

Tldr; I have a fresh 48v battery and charger around less than 3 months old. Very intermittently when trying to charge the battery the charger will power up, the fan spins up and then it starts to make a nasty buzzing / whirring sound. Its pretty loud normally but this is something else.

My discovery since the last post is that I no longer believe this is a broken fan issue, as I know that can make a lot of noise. I will not dismiss the possibility by any means though. Main reason for believing this is that when I charge at home it boots up fine and lightly whirrs. But more often than not I have noticed when I am charging in my place of work, this weird sound starts like clockwork almost as soon as I turn it on.

I can be entirely sure of this but id say i cant remember it once doing it at home, but its happened around 10 times now in work. Sometimes it can charge fine even on the supply, it is kind of odd.

I have attached a picture of the charger and a video sample of the noise it makes.

It is a generic style chinese brand charger so criticise if you wish but this is brand new, CE and RoHS tested.

Any help or SUGGESTIONS FOR A NEW CHARGER using the bespoke connector it has would be GREATLY appreciated.

The charger is a generic-style C300 model battery charger, similar to the one shown below:
https://i.imgur.com/a1vYr7K.png

[Charger noise video]
https://streamable.com/1kmpr

[3 Pin DIN style connector, not XLR]
https://imgur.com/a/4oqjeRB

Even though the design may be CE compliant, the unfortunate reality is that cheap manufacturers will still leave out "unnecessary" circuit components or replace them with fake ones when actually building it.  (RoHS just means it's free of lead and mercury etc etc, nothing to do with quality or usability of the electrical design.)

The components that are supposed to filter and reject electromagnetic noise are common victims since they're both expensive and it "normally" works just fine without them.

So if it works fine at home but makes weird noises at work, it seems more likely there's a failing connection in the electrical power system at your work putting a lot of noise on the line, rather than a problem with your charger.  (Other than potentially failing to reject an amount of noise that other DC supplies in the building seem to be handling, whether due to a lazy design or corners being cut in assembly.)


What is the minimum carb intake to not bonk (but also not put on weight)? Going on long bike rides (or otherwise doing any form of endurance workout) can result in "hitting the wall" or "bonking".
The well-known solution is to be mindful of one's carb intake.
But very many folks go on long bike rides (or other endurance workouts) precisely for this reason: to force their bodies to break down fat.
Can someone who is not trying to lose fat (and who really doesn't want to lose weight) take some inspiration from those folks and avoid hitting the wall? Surely they do not practice carb loading (before), gel supplements (during), and glycogen replenishment (after) a ride.
Why is it interesting (and important) to know—even for those who are not trying to lose weight, or who actively do not wish to lose weight? Because it is easy to overdo the starch intake, and so knowing what one should do at a minimum to avoid bonking will also stand as a useful limit. In other words, the cyclist can then "do this" and also take some extra carbs, rather than simply indulge in carbs "to be on the safe side".
It is clear that by erring on this minimum one will be taking the risk of losing fat, but then it appears that even the most athletic still have fat.
I hope an answer is known
without
using
supplements, by using only what grows on trees or is raised in farms, rather than what comes out of a chemistry lab or a factory.
Two options are possible:

Conceivably, the answer may be "it cannot be done," or: taking inspiration from those who succeed in losing fat means that one must also take a risk, and routinely suffer from bonking.
Earlier this summer, with gyms closed, I bonked on two occasions right after picking up road biking, but this was a fluke. My "glycogen stores" were pathetically low. They may have now improved enough that I need not worry about bonking.

Epilogue
To appreciate just how difficult it is to get this right, read the comments under this answer.
In retrospect, the question I wanted to ask (too late now!) is: What is the minimum carb intake that will be certain to neither: 1- make me bonk, nor 2- "cannibalize" my muscles. When initially asking the question, I expected a simple continuum. Imagine a line with zones A, followed by B, followed by C. The diet in zone A ensures no bonking (that's easy: eat lots of carbs. Drawback: it'll also be too easy to put on weight). The diet in zone C makes the rider lose fat (as many questions here show, that's hard). The surprise is that even identifying just zone B—the objective of this question (no bonk, no targetting of fat) is hard. Oh well!
And if all this is not tough enough to understand, I don't actually mind losing fat, but since my BMI is quite healthy, I suspect my body will end up rebuilding these fat reserves again. The next question in this sequel is then: does one's liver get exhausted from so much work (metabolize fat cells, rebuild fat cells, repeat) ? If you understand enough about all this, feel free to formulate that question as a proper question.

What is the minimum carb intake to not bonk (but also not put on weight)?
Simple Answer: 30-60g of carb per hour to not bonk (can't comment on the weight bit though).
*Real answer:
There is no calculable answer for these reasons:

The type of fuel you burn is dependent on the intensity of the
exercise (heart rate zones)
The amount of fuel you burn is dependent on your efficiency
The starting amount of fuel is determined by your diet and build

Fuel Type
At "walking intensity", you burn fat, and because fat is so energy dense even a very lean person could walk for days without running out of fuel and bonking.
At higher intensity, you burn a mix of glycogen store from your muscle and sugars being digested from the food in your gut.
At very high intensity, all energy is directed to your muscles and so your digestion stops and you will be relying purely on glycogen stores.
Note that fitter athlete will be putting out more power for the same heartrate, so how your body responds is specific to you.
This conversation is about carbs, so you would need to know the intensity at which you'll be cycling to know what fuel types you'll use in what proportions.
Fuel Amount
Every body works differently, and many variables go into how efficiently you can convert fuel into power output. For cycling, things like how good your bike fit is, your fitness level, your years of experience on the bike, injuries and flexibility can all affect your efficiency.
For this conversation, this variable is basically unknowable. Professional athletes might have a good idea of their efficiency, but it would be pretty rough.
Starting Fuel Reserves
You start your ride with your glycogen stores and the contents of your stomach. It is easy to control the latter by making the meal before riding carb-rich. Glycogen stores can also be optimised by carbo-loading. There is a university study (that I can't find right now) that demonstrated that in the 24hr before an activity, the athlete could more than double their glycogen stores by eating ridiculous amounts of carbs.
For this conversation, your general diet and you diet in the last 24 hours would be very relevant.
Conclusion
While there is a generally accepted minimum carb consumption to avoid bonking (30-60g of carb / hr), the specific question also required not having surplus energy intake an so to avoid putting on weight. The question requires an exact calculation, which is not possible.
Relaxing the constraint on "exact intake" but keeping with the spirit of the question, the suggested solution is to eat lots and ride even more.


Is there a way to rest at an intersection without (partially) dismounting the bike? I have seen this done, and it probably has a name or another way of describing it that I have not thought of, but I cannot find information about it on the internet.

When stopped at an intersection, some cyclists will turn their front wheel to the side, and it seems to help them stay on the bike while the bike is not moving forward. Unless I'm imagining things.

I'd like to know how to do this, how it works, etc.

It called a track stand. It originates in track racing on a velodrome, where in the opening stages of the individual sprint event you sometimes need to come to an almost complete halt. Tricky and dangerous to do if not well practiced, it can end in a 'sprawl of shame' if your technique is not perfect.


Old STI 105 shift lever fell off Hello,

While riding home last night, my brake lever fell off. It's an older item on an older bike. What's the process to re-attached one of these?

You say you've lost some of the other bits.  This kills the brifter.

Seriously, just buy a replacement, probably you can find it used for $50.  Normally you'd redo the bar tape in order to replace the entire shifter, but if you want to avoid that, you could probably swap the entire internals of the new unit into the old body (I say probably because it may be a bit fiddly and perhaps not worth the trouble, and everyone needs new bar tape anyway!).


Front wheel requires weight for traction: is this applicable to icy conditions? How is cornering on the road different than cornering on dirt?
Is cornering in snow any different?

I usually attempt to keep at least half my weight on the front wheel for stability when cornering and braking.
However, with all the ice this winter, I discovered that front tire slips are quite ordinary. Thus, I find it beneficial to keep my weight back, maybe only 20% on front wheel, and stay ready to dab in the event of front tire slip.
Is this reasonable behaviour on ice or am I being too scared and actually decreasing my stability by pulling back? Tires are Land Cruiser, saddle height is lower than typical XC to facilitate ... falling from not so high.

I'd look at which situations you are encountering tire slips in.  If you are encountering tire slips in cornering, studs are probably the way to go (or much more conservative riding).  If you are having trouble while you are braking, you may consider adjusting your technique to be much more rear brake heavy or rear brake alone.

I find that no matter what I do my pedal stroke is so sloppy and unbalanced that I almost never pedal on ice.  Generally I just try to coast over ice sections keeping my body as relaxed and centered as possible.  Major direction changes (without studs) are pretty much out as well.  I try to keep my weight off my handle bars so that I am not tempted to move the front wheel quickly or with any real force.  If you are going to try and turn the front wheel, it should be a feathered movement.  More than anything it takes practice and watching out for icy spots.  I probably fall (on ice) less than once a year now.  When I started riding in the winter (even with studs) years back it was probably closer to every other week.


Is a Vittoria Randonneur 28- or 32-622 on a hook-less 23 mm rim feasible? My new bike came with rims that have a 23 mm flange distance. There is no hook to hold the tire's bead though. A 32-622 tire (Maxis mud wrestler) is paired with it.

I also got a set of a 28- and a 32-622 Vittoria randonneur tires.

Common knowledge (see link below) says the former wouldn't be safe. I am not entirely convinced that this is always true today.

The 28 likely is too narrow for that rim, is it?

Would the 32-622 do?

I posted a related question where I tried to abstract the problem to make it more generally useful:

What is the smallest width of a tire for a given rim width?

Hookless is getting more commonly seen and will probably become pretty normal. More analysis here: http://www.bikeradar.com/us/mtb/gear/article/trail-tech-off-the-hook-40749/ . Basically, the bead lock area of modern tubeless compatible rims diminishes the need for it. For this kind of rim (very short sidewalls, center mounting groove, bead lock), lack of hooks shouldn't be a factor in figuring out what width to run.

What will actually get you in trouble, or keep you out of it, when determining how narrow you can go is how much tire you have overhanging the outer sides of the rim, which protects the rim from dings and scrapes. A reasonable minimum is 1-2mm per side, and never a tire whose inflated width is narrower than the rim. (There are some trends in the racing world to break this rule, but rims suffer as a result.) Internal width is a relevant consideration, especially in gaging how wide you can or should go, but it's not the end-all factor that it's sometimes made out as these days.