How do you evaluate a wheelset? I'd like to upgrade my wheels but beyond the price, I'm not sure how to compare different options or even to tell if a given wheel is an upgrade or a downgrade from my current wheelset. I'm looking for an improvement in performance in aerodynamics, weight and reduced rolling resistance.

There's a huge array of wheels available. Ranging in price from $100 to many thousands. What do you look for in a quality set of wheels? I assume total weight is one of the most important factors, but I also imagine that low resistance in the hubs would be at least as important.

I have many questions:

What's the most important part of the wheel? Hub or rim? Or both?
How do you evaluate or compare different hubs?
How do you evaluate or compare different rims/spoke combinations?
Are there other factors I've missed?

EDIT: What I want to establish is that if I'm comparing two wheels in a showroom or looking at their technical specs, how do I tell which is better and whether they're good value for money or not.

I'm looking for an improvement in performance in aerodynamics, weight and reduced rolling resistance.

If this is what you want then you can pay for light hubs with high quality bearings that give you low rolling resistance.  The rest of rolling resistance is due to your choice of tire and tire pressure.  Be aware that the claims that weight on a wheel is more important than weight on the frame is based on an evaluation of weight at the perimeter of the wheel, not at the center so the weight savings of the hub may not be as critical as weight savings elsewhere in the wheel.

Aerodynamics-wise, low spoke count wheels are better.

  Fewer spokes means decreased stiffness and spoke life, while additional spoke
  counts can lead to higher power requirements, or overly stiff wheels which are punishing on rough roads.

Low spoke count wheels are not necessarily lighter though -- I believe most low spoke count wheels use heavier gauge spokes and nipples to compensate for the higher tension -- the bigger nipple spreads the force over a larger area of the rim to prevent light rims from buckling.

(Leaving the rest here so this answer is useful to other readers)

It depends what you're going to use the wheel for, but I'm answering assuming you want a reasonably light durable wheel that you can fix yourself if you have a breakdown, and that you don't have a van pacing you with spare wheels.

  What's the most important part of the wheel? Hub or rim? Or both?

Spokes.  A low spoke count wheel on a high quality rim and hubs is still a crap wheel.  Low spoke count wheels require each spoke to be that much more highly tensioned.  Low spoke count wheels are made by machines that push on the whole perimeter of the wheel as they tension the spokes.  No human can do that on the side of the road, so this means that if one spoke breaks, you have no real chance to retrue the wheel by tightening or loosening other spokes to compensate.

High spoke count wheels (36 spokes for example) may have slightly higher drag, but there's so many spokes, that you can actually use that little spoke wrench that comes with your multi-tool to do road-side repairs.

  How do you evaluate or compare different hubs?

Look at reviews.  You basically have to relace the wheel every time you go through a hub, so I prefer long-life over lighter-weight, buy YMMV.

Phil wood is my personal favorite, but again, probably not ideal for racing.

  How do you evaluate or compare different rims/spoke combinations?

Jobst Brandt's book "The Bicycle Wheel" explains spoke lacing patterns.

Major rim choices include

offset vs centered spoke holes.  You can get less dish (see below) sometimes by using offset spoke holes
depth of rims
thickness of material.  Thinner is lighter, but if you're going to do a lot of wet weather riding and you have rim-brakes, then grit gets into the brake pad which will wear down thinner rims more quickly than thicker rims.
material.  Some people actually sell Carbon Fiber rims but if you're using rim brakes then you want the rim to be made of a heat-conductive material so it sheds heat well.  Carbon fiber does not.
type of tire.  Clinchers vs tubular.  If you don't know what this means, then you're using clincher tires which have a metal (or kevlar) bead, a stiff wire that runs around the inner perimeter of the tire and presses it against the rim.

  Are there other factors I've missed?

Dish.  If you have a derailleur on one side of the wheel, you can't quite center the wheel over the hub so you have to use longer spokes on one side.  This means you can't get both sets of spokes up to the same tension you could if you didn't dish the wheel resulting in a slightly weaker wheel.


Replacing FSA Omega BB30 with SRAM Force 22 BB30 following my recent post about the problem with FSA Omega BB30, I was advised to throw it away and go for a new one.

I've done some research and decided to upgrade with SRAM Force 22 BB30, already ordered it. Now, my FSA had 50/34 teeth and the new SRAM will have 53/39. Obviously, I will be looking for a new chain but my main concern is whether it is compatible with the Shimano CS-HG500 cassette that I currently have.

Also, since I have FSA's BB30 bottom bracket already installed, I assume that the Force 22 should be compatible, or am I wrong?

If you know any other problem that this upgrade might cause or anything that I should look out for, please let me know.

Cassette compatibility is not a concern, cassette sprockets don't care what's on the other end of the chain. BB30 crank will fit right into the BB30 bottom bracket. Front and rear derailleur capacity will be fine because you have less difference between chainrings (53-39=14, rather than 50-34=16).

You currently have a 10 speed drivetrain, and the Force 22 crank is for 11 speed. Chainring spacing is slightly narrower for 11 speed cranks as 11 speed chains are narrower than 10 speed chains. The opinion on this site seems to be  that you can mix 11 speed cranks into 10 speed systems and vice versa.

As you say you will need a new chain because the length will need to be longer. You might consider a new cassette as well so you have a full new drivetrain. Front derailleur will need to be be moved up to accommodate larger rings, check this is possible on your bike. You should also check that your chainstays have enough clearance for the larger rings. A 53 tooth ring is about 6mm greater in radius than a 50, a 39 tooth about 10mm greater than a 34 (see this question).

My main concern would be compatibility with legs, as you will have a substantially (15%) higher spread of gear ratios. If you live in a flat area and never use your lowest gears you are probably OK, but if you are using your full gear range you may want to reconsider and stick with a 50/34 crank.


Biking with spinal disc herniation I was diagnosed with lumbar spinal disc herniation and told that I should exercise. I always liked biking, so I want to do that.

I have an older rigid mountain-bike and will be mostly driving on asphalt bike-roads. I know I should pay attention to bumps, so I stand up and use my legs and arms to take the hit.

Are there any more precautions I should take or things to avoid?

To be very to-the-point, in your situation I would first consider the following two things:

Rise/exchange your handlebar to leave it at least some 8 inches above the saddle height;
Have a good quality suspension seatpost.

I have studied medicine (and have a little back pain, also), so the rationale is the following:

This figure illustrates a part of the lumbar spine, as would be seen if the rider was passing from right to left on the bike (left is front, right is back).

Rising the handlebar would allow you to be more erect, thus making the upper vertebrae rotate backwards (clockwise in the figure) over the lower vertebrae. Since this rotation is articulated a bit behind the midline, there is a decompression of the discs (blue and red, with red being herniae and blue being normal disc tissue);
Since your bar is now higher, a greater part of your body weight is supported by your back/buttocks. Using a suspended seatpost - a relatively lowcost, minimal modification on your current rigid bike - helps avoding unpredicted/unavoidable impact, which is a main causation factor of hernia inflamation and/or progression, due to the sudden rises on internal disc pressure associated with impact.

I don't enjoy very much the feeling of sprung saddles (I have a Brooks Flyer), and I think that's because they pivot around the nose, thus bending the lower back and pelvis while going down, in a flexing motion. Seatposts, on the other side, have a translation movement, without pelvis rotation.

Having ridden some suspended-seatpost-equipped bikes, I can say one thing: they are awesome! And since you have a condition, thus are probably not wanting to become world champion anymore, the minimal, questionable performance decrease is overwhelmed by the very significant gains in comfort and health risk reduction.

Hope this helps!


Rear derailleur adjustment screws My rear derailleur adjustment screws are in a vertical line there is no scew indicating inner and outer.  Without removing it I can't see which screw is touching at each side of the cassette. Does the upper screw relate to the big cog or the little one?

If you look straight down into the space between the parallelogram sideplates, you may see that the outer plate has a “feeler” that contacts one limit screw, and the inner plate a feeler that contacts the other.

If that doesn’t work, we can’t guess without knowing what kind of derailleur you have, and you can probably find service info on the manufacturer’s website.


Pedal snaps at every rotation I have a bicycle that after a some amount of use (at least 3000 kilometres since I bought it from someone else) began having some problem on one of its pedals.
Basically at every single rotation, there is a snap in some place, like if there was a crack inside the pedal. That snap its almost impossible to feel when going low on pressure applied, but reasonably felt when running at normal speed, and feels like something is definitely not right and its going to break when either sprinting or climbing.
The closer to the left the foot is, the less I can notice it, (its the right pedal), what can be the cause?
Is it too dangerous to keep going with it this way? By dangerous I mean, the pedal simply getting lose or something like that and go off the bike.
The weird thing is that its a fully metal platform pedal, like this one:

What is there to break? Aren't these pedals just a shaft and the solid outside of the pedal?

There are bearings inside the pedal that are meant to keep things running smoothly.  If it was just the pedal itself around a metal shaft, then things would probably wear out quite quickly. Some pedals are serviceable, while others are meant to be replaced completely.

If you are sure that the snaps is coming from inside the pedal, and not from inside the bottom bracket or where the crank arm mounts to the bottom bracket, then it's probably a good idea to just replace the pedals.

New pedals, especially platform pedals, can be obtained quite cheap and can be replaced basic tools you may already have.  If you don't have tools, the bike shop would probably install them for free if you asked nicely.


Changing rims from 29 inch to 27.5 inch, V-brake problem I own an old MTB bike, it's beaten up and I'm planning to restore it.
Everything is already done, groupset, crankset, the fork, etc.
The MTB itself is a 29 inch frame and since I want to give this bike to my adult friend with height only 158 cm, I want to change the rim to 27.5 inch
Here lies the problem, the V brake is not low enough to grip the tire when I try to brake
Any solution?
Thanks

The best solution is to use a frame that is designed for 27.5" wheels. For other problems related to wheel size change, see Do 27.5" wheels fit a 29" mtb?. When riding bike you touch the handlebars, saddle and pedals. If the frame is too large, smaller wheels don't help
If you really have to use this exact frame and either have cash to throw around or live somewhere where labour is cheap, it might be possible to add a second set of brake mounts (but find someone who understands welding and heat treatment to do this, especially if the frame is aluminum).


Bottom bracket conversion with rare cups I'm asking this question as I'm interested in the community opinion in the idea of "am I taking the right path" or "is there a better way".

  tl;drl; - scroll to the bottom, please.

Namely, almost two years ago I've committed a (successful, in my opinion) conversion of cottered bottom bracket to a square-tapered one on a Motobecane 2040 steel road frame (late '70s or early '80s).

Why, one may ask. The reasons are:

I got the frame for a very attractive price and wanted to build a fixie on it (succeeded)
I hate cotters - they say you need only a hammer and a wrench to install and remove one, but in practice I never managed to do it properly (or I'm abusing my bikes). For square tapered cranks you need allen key or socket wrench for installation and a special crank remover for removal (sockets and allens I already had and the removal tool is like $5)
I was aiming for maintenance-free riding (also in bad weather), thus cartridge bearings were a very good option. If the set gets excessive play I'd rather replace the bearings or the complete cartridge than overhaul the ball bearings, set the play, check it and adjust after some time, etc.

So what was the challenge?

it is a Motobecane frame, where the BB threading is neither typical French, nor BSC (a.k.a. BSA), nor Campa, hence an off-the-shelve cartridge bottom bracket set with cups (either nylon or aluminium) is nearly unavailable
there are BSA axles available, but the BB shell on Motobecane is a bit wider so without replacing the balls it won't work. And again - it wouldn't be weatherproof.
the drive side cup was seized (i didn't have impact wrench then)

After an evening with Vernier caliper and internet, sourcing for affordable parts I've came up with a brilliant idea - I would keep the original cups and find a BB cartridge that would fit them. It was to be done. the cross-section of the whole concept (proven, working, nota bene) looks like this:

Black is the BB shell,
Red are the original cups (with bearing races),
Green is the Miche square-taper bottom bracket cartridge.

Positioning of the axle is done by placing some shims (ground to size) on left or right side.

The whole setup is working correctly now for more than 1000 km. The retaining nut came lose once, in fact I've assembled everything to check my proof-of-concept and it was working so well that I forgot to tighten or thread-glue the setup. After fixing that I'm experiencing no problems whatsoever.

Soon I'm going to build a daily commuter for my daughter based on Raliegh Ladies Traveller (something between the '30s and the '70s) frame (which we got for free and she really liked shape of the frame and front fork). As it is Raleigh, the bottom bracket has proprietary threading, which isn't BSC (a.k.a. BSA) - I've already checked it.

  TL;DR; reference:
  My question is:

shall I go the same way I went for my Motobecane, or
do you know some better way to convert the bottom bracket for the frame with non-standard cups?

Btw. both cups (undamaged) are now degreasing in a bucket, threading in the BB shell is also in very good condition.

Depends on

How much you value originality,
The thickness of the metal at the cup threads
The internal diameter of the cup hole.

Either keep it totally original, which means scouring ebay for old bike parts (expensive)

OR look at retapping the BB shell to accept a modern cartridge bearing unit.  This is probably beyond the home mechanic because it will require a large tap and a way to keep it completely straight.  A frame builder might be your best contact.   A BB cartridge is cheap, common, and easy to change IF the threads match, and the width is workable.

OR see if there's some combination of press-fit BB that will fit in the BB shell.  I'm not familiar with these, but there was one where two parts entered and threadded themselves together in the middle, allowing a hollowtech axle to go though.  Would increase Q factor and might look a bit weird.

OR your proposed hack should work just as well on the Raleigh as on your bike.  Downside is if it needs servicing and you're not available to do it.

This is an interesting question - please consider posting your own answer, ideally with progress pictures.


Are Shimano 10 speeds going away? My LBS claims that Shimano's 10 speed groups are going away forever. They told me that if I don't upgrade to 11 speed that my next replacement will cost me an arm and a leg because 10 speed components will cost more due to a shortage. I've googled and checked here but found nothing to support their claim. Maybe I'm looking at the wrong place to get my news, so is Shimano discontinuing 10 speed road bike components, and should I just upgrade/get a new road bike to future proof my rides?

Bike: 2007 Specialized Tarmac Expert Duo

They're trying to sell you stuff. More expensive stuff (have you looked at 11 speed consumable (chain+cassette) prices vs 10 speed?).  I would not bother upgrading.

As groups go to higher and higher speeds, the older stuff gets pushed down to lower component levels. So today's 11 speed 105 group will be next year's (or likely a few years later) Tiagra group (with some minor modifications). They're generally completely compatible with the previous higher end stuff. The price might change a little bit higher or little bit lower, but it won't be bank breaking (in fact, I'd guess it will go lower, at least for a few years). And let me remind you that we still have an 8 speed road group, despite 8 speed being 20+ years past introduction (heck, 9 speed is nearly 20 years old and we still have a ton of parts on the market from shifters,cassettes and derailleurs; 10 speed is only a mere 12-ish years old; 7 speed stuff is still in abundance, though finding quality components has started the incentive to move 8 speed).

So, you should be good for quite a while sticking with the 10 speed stuff. Unless you need the shiniest fanciest stuff for some reason. Plus, if you do decide to go 11 speed for some reason later, it will be cheaper than doing it now.


Should tyre sidewalls appear cracked so quickly? I fitted a brand-new pair of Schwalbe Marathon Racer tyres at the start of this year. I've just noticed that there are quite a lot of very small cracks in the side wall of both tyres. (The tread is still good though). Even using a worst-case estimate, I've only done about 3200km this year. Schwalbe say the Marathon Racers should last at least 5000 km?

The cracks are very small, somewhere between Fig.1 and Fig.2 on the website. The bike has been stored indoors when not in use. They have been great tyres but I'm wary of spending that much on tyres if they need replacing every 8 months.

The cracks look like this in various patches most of the way round both sides of each tyre.

Addition:
Took the tyre and inner tube off to inspect. I can't see anything like the 'ripples/waves' in the Schwalbe pictures. Most of the slits are in the same position as those pictured above, i.e. between the start of the tread and the dynamo track. (A few are slightly lower though).

This doesn't seem like a terrible issue. You should be able to ride on these tires for awhile longer. I've seen people with super cracked tires ride for multiple months without issue.

Oftentimes, cracks like this happen because of over inflation and exposure to the elements. To keep the tires viable for as long as possible, I would recommend keeping the bike inside when you're not using it, and leaving the pressure between 60 and 80 psi.


Are bicycles with wide tires bad for road racing? I have Schnell Damping 26, which is a mountain bike with front and rear suspension. Some people suggest me that thick tire bikes are not good for road racing. What is the reason? Also, some suggest that back rear suspension is not good and causes a lot of sweat.

Wide tyres are designed to be pumped to a relatively low pressure so that they bend around objects they roll over, to give grip and a smoother ride. They also often have lots of bumps and lumps on them: again, these dig into the ground and bend around things for more grip. However, bending and deforming all this rubber hundreds of times a minute takes a lot of energy. The only source of energy on a bike is you, so this means that a lot of your energy is going into the tyres, rather than driving the bike forwards. Sometimes, you hear a mountain bike with really knobbly tyres being ridden on the road and it sounds like a swarm of bees: that's a lot of wasted energy.

Suspension (front and rear) is, by design, flexible. This means that, when you press on the pedals, some of your energy goes into driving the bike forwards, but some of your energy goes into flexing the suspension.

Roads are relatively smooth, which means that fat tyres and suspension aren't giving you any advantages. But they're still there, using your muscle power for useless things. They're also heavy, which makes it harder to accelerate your bike and harder to go up hills. These are significant disadvantages to using this kind of bike on the road. Another disadvantage of mountain bikes is that they often have very low gearing, which means you can't go very fast, even spinning your pedals as fast as you can.

Some bikes with suspension have a control that lets you stop the suspension moving. That would be a good thing to use when riding on the road, but you'll still be carrying around all that excess weight and your squishy, fat tyres.

And, in fact, you might not be allowed to ride a road race on your particular mountain bike. The international regulations of the UCI require something fairly close to a traditional diamond frame. The intent was to exclude some of the extreme aerodynamic designs that people were experimenting with, but a mountain bike with rear suspension would also probably be forbidden under these rules. Although any race you'd be likely to enter wouldn't be run by the UCI, local cycling federations usually use rules very similar to the international ones, so that the rules don't suddenly change when people turn pro.


suggestions of affordable clothes for beginner rides? I am new to riding.  I have done some research, and found out there are plenty of guides telling people how to pick up cycling gear.

But I want suggestions for affordable, good quality clothes. I need advice from someone who actually bought the clothes. I don't need expensive cycling clothes like alpha, as I only ride once per week.  Any tips for beginners are welcome.

I need suggestions for both summer and winter. I am a man. I've been thinking about around 20 miles at the beginning.

For a beginner, as long as all the required naughty bits are covered, and you're comfortable standing and walking in those clothes, then they're generally fine for cycling.

A beginner is anyone tootling 3 kilometres/2 miles each way.  If you're regularly doing rides of 16 km/10 miles then that's about where cycling clothing will come in handy.

There's no need to go silly with race gear.

The first specialist items to consider are

Padded pants or shorts or bibs  like http://www.dx.com/p/top-cycling-cycling-silicone-cushion-underpants-for-men-black-l-258557#.VnPkpW_4ugo for $10 US or bibs like  http://www.dx.com/p/2012-bike-bicycle-cycling-padded-bib-shorts-black-size-xl-125561#.VnPioW_4ugo   You're after something between your backside and the seat, and ideally pants to give some compression on your knees.
High visibility top (NOT BLACK!) like http://www.dx.com/s/NJ600  Under $20 US  or http://www.dx.com/p/spakct-stylish-sleeveless-cycling-jersey-t-shirt-fluorescence-green-l-227832#.VnPknG_4ugo
Gloves, I just wear $2 white gardening gloves from the local hardware shop.

I have bought all these things and they work fine for me.  My longest ride was last weekend were I did 118 km.

Other than that, check this site for "what tools to carry on a ride" and nutrition/hydration questions.  However that's bike gear not clothing so only a brief reference.


Road bike handle bar adjustment to one weaker and shorter arm I have Erbs Palsy causing my left arm to be shorter and weaker than my right arm. Can the handle bars of a road bike be adjusted to accommodate this or is there another resolution I can consider?

For a small difference in reach, it could be a simple as adjusting the position of the hoods on your handlebar such that the left one sits a little higher and further back. It's a change that will often look small, but it adjusts the angle of the lever at the same time, which amplifies the change too.


Difference between brake pads on road and MTBs I know that road caliper brakes use shorter (and wider?) pads than v-brakes and MTB cantilevers, but I don't exactly understand the reason behind.

What would happen if I mount longer pads on road-style calipers and vice versa?

When you open the quick release on your caliper brakes, the brakes open wider to allow you to release your wheel quickly without deflating your tire. Longer brake pads could then touch the frame or fork and chip the paint. Some people even trim down their canti brake pads to avoid this scenario and sometimes in an attempt to reduce brake shudder.

Additionally, most v-brake style pads come with a series of washers (one concave and one convex that on either side of the brake arm you bolt to) that allow some angle adjustment which allows you to set the toe in and angle of approach on your brake pads without bending the brake arms.  This is available on some brake pads intended for caliper brakes as well, but the washers tend to be much smaller. The extra washers may also prevent you from removing the wheel without deflating your tires.

But will these pads stop you? Yes


can you use a cycle path to bypass red lights? Okay, so this is my issue.  On my commute home there is a spot where there is a light straight ahead, before the white line the cycle lane mergers with the path on the left.  Does this mean i can bypass the light, or am i jumping it if it is red?

The light controls the stop line (and, if there is one, the advance stop line).

I can't tell from the streetview image, or from streetview itself or the satellite view, whether the cycle path moves from the road to the footway before the stop line or not.

If it does - you don't have to cross the line, and the light doesn't affect you (so long as you follow the cycle path onto the footway).

If it doesn't, or if you choose to stay on the road, you'll be crossing the line and controlled by the light.


Use 105 crankset on 9x2 Sora equipped bike Want to ditch my basic square taper FSA Vero (50/34) crankset on 9x2 speed Sora drivetrain (2018 Devinci Silverstone 2) in favor of 105 compact crankset. I will attempt to get one in 50/34 not to mess up gearing.

First of all because it's FSA square taper, secondly 105 is lighter and I can get it locally used in great condition.

Obviously I have to replace the crankset and BB  Potentially reuse BB (RPM, Square taper JIS) and FSA crankset in my old Raleigh rebuild, but this is separate story...

Asking if it is possible, if Yes what I have to take in account when doing this.
Thank you

A 2018 bike with have an R3000 Sora 9 speed groupset.  The problem here is that you have a 9 speed chain that probably won't shift well on an 11 speed crank.

As 10 and 11 (and now 12) speed systems were created, the cassette sprockets needed to be more closely spaced, which required the outside width of chains to be decreased. The distance between crank chainrings was also decreased to accommodate the narrow chains. The 105 crank will have the wrong spacing for the wider 9 speed chain.

A safer option would be to upgrade to a external bearing Hollowtech bottom bracket and a 2-piece Sora crank, or an equivalent 9 speed crank and BB from another brand such as FSA.


How do I reassemble the rear gearing after fitting new tyres? I have a Raleigh maybe 8 years old with shimano 15 gears. How do I reassemble the rear gearing after fitting new tyres? Everything seems to be in correct position but a small bolt with captive nut seems to fit in a triangular hole above the axle, on frame but this then throws the gear all out of position. Any ideas?

Sounds like you're placing the tire back into the wrong gear to begin with. Always remember what gear you left off on as it can ruin your entire setup in a matter of seconds.


Headphones while cycling Possible duplicate: Is listening to music dangerous while cycling?

I cycle 12 miles to work (and the same back) of which the first 5 miles are on a cycle path away from the road and the other 7 are on the road. I go very early so see no other cyclists and therefore listen to music on the cycle path. I then take either both or sometimes just one ear out when I hit the road section.

I realise the argument is that any kind of distraction is not a good thing, but in my opinion, as someone new to commuting by bike, when I am cycling, I hold my line, check over my shoulder before moving over to pass parked cars etc, and do everything possible to avoid the chances of an accident.

The main dangers I can foresee are someone not giving me enough room when passing, or someone pulling out from a side street. I am very well lit and I can't see that having headphones on would prevent either of these accidents from happening.

My question is (Ive got there eventually!) has anyone ever had an accident while wearing headphones that could have been avoided if they hadnt had them on, or has anyone had a near miss without headphones that would have been an accident if they had have had headphones on??

Any kind of sensible response or argument from this will help to convince me that headphones are bad news as at the moment i'm not sure that I am actually in any more danger with them on

The trouble is, you might be the most sensible, perceptive guy on this earth, with bike handling skills second-to-none.

But you have no idea who the dick in the car is.

As Javier says, play the odds and give yourself the best chance possible.


Rescue corroded alloy nipples on wheel spokes, perhaps using chemicals? My wheelset has alloy nipples which have severely corroded.  It needs rebuilt with brass nipples.

However, my LBS can't get the spokes out.  The nipples are too disintegrated to turn, but not disintegrated enough to just crumble to dust and release the spokes.

The LBS says the only option is to cut and replace the spokes.  This will be expensive (multiples of the cost of a simple rebuild using existing spokes).

My questions are:

Any suggestions how to get the spokes out?
Specifically, are there any chemical tricks to accelerate the corrosion and entirely dissolve what remains of the nipples (without damaging the rims or spokes).

The wheelset has carbon rims, steel spokes, high-end straight-pull hubs, and alloy nipples.

In many other cases I'd apply heat (to the spoke) but I'd be wary of doing that here, because you could end up tempering part of the spoke, while it's still under stress. If you're unlucky that would lead to weakening. Also you don't want to get that much  heat too near the carbon rims.

If you can get a few spokes right off, you may be able to slacken the wheel enough to flex the others and crack the bond (pliers on the nipples) or even to push the last few clear of the rim for more grip. This also means you can try different methods on different sections.

You haven't said how much nipple is accessible, but with enough access you could file or dremel a slot (nearly) parallel to the spoke without going right through, then put a screwdriver in the slot and twist to split it. You'd need to split it over a decent amount of thread though. In my touring rims that would be possible. I suspect your rims are rather different, and they'd only need to be a little aero to deny you access to any thread.


Is it a bad idea to take a commuter bike for a 50 - 100km ride? I'm a reasonably new rider so excuse my ignorance, but I'm thinking of taking my commuter bike for a 70km ride some time in the near future.

I have recently been on several 30km rides without issue and recently had my bike serviced and adjusted.

The majority of the ride will be in light traffic and there is a shoulder where cyclists regularly ride, so the main concern is not safety. I also consider myself fit enough so fitness should also not be an issue.

So what are the negative aspects of doing this?

Reliability
True commuter bikes are built for day-in and day-out reliability. As far as breaking down, you have little to worry about as a commuter bike is designed to take massive amounts of abuse and neglect and still function. While you could have a part failure like any other bike, these are uncommon and the most frequent (the flat tire) is easily fixed. On a group ride, someone will likely have a repair kit in their bag, or if you are more proactive you can carry one yourself.

Comfort
While commuter bikes are designed with comfort in mind, they do not have long distance comfort in mind. In particular, a commuter/comfort bike with a wider saddle may prove to cause more chafing on a long ride like this than a narrower and seemingly less comfortable road saddle. Also, depending on your handlebar setup, there may only be one legitimate hand position - which means your body is, by default, forced into one position for the ride. In both cases if after your 30km ride you did not have issues, than whatever issues arise on this longer ride will more than likely be tolerable. While it may not be ideal, you are not going to get any serious injuries due to the bike setup.

Speed (energy expenditure)
Compared to road bikes, commuter bikes can be slow and heavy. You will spend more energy going the same distance, but if you have the fitness and patience to do so then it's a non-issue, unless you are riding in a group with fit riders on faster bikes where you may hold the group back. Additionally in a strong wind you will have a harder time in an upright position then on a road bike with drop bars, where you can tuck forward into the wind.

While there are better bikes built for longer distance traveling, there is no reason a fit person couldn't finish a 50-100k bike ride on a commuter. Since you have completed 30k I don't think 50k will pose a major issue. If you step up the distance incrementally you will know where your physical limit is. Enjoy your ride!


Loading training plans on to Elemnt Bolt for free How would one go about loading training plans onto a Wahoo Elemnt Bolt without using an app like trainer road or training peaks? Is this even possible? I'd like to use a free tool on my laptop such as Golden Cheetah or something similar.. I'm not looking to create complicated workout plans, just simple interval sessions that I can follow out on the road.

As per @andyP's comment:

  It's not currently officially supported, but I found some info you might find useful here: ergdb.org/load-workouts-onto-your-wahoo-elemnt-on-a-mac Kept as a comment rather than an answer as I think wahoo will improve support and outdate it rather quickly

This worked fine, the file transfer app on the mac is a bit flakey, but I got my workout on there just fine.


swapping crankset and chainline compatibility I'm looking into placing a power2max powermeter on my bike, which is full Ultegra equipped (R8000). Now, the chainline specs of the crankset from p2m are either 45mm or 46mm (depending on the brand of the cranks), whereas Shimano's FC-R8000 specs at 43.5mm.

Are there any issues in swapping the cranksets, or am I facing some trouble or sketchy adjustments?

Yes, that's enough to create situations where you may have chain rub that can't be adjusted out in some additional gears on most road bikes. There are other factors, namely chainstay length - bikes with "pushed" chainstay lengths, i.e. 405mm-ish or less, are notably more finicky about this kind of thing.

How important this is depends on your riding habits.

It sounds like you're looking at a power crank with a chainline that's either oriented more towards a road disc rear end (135mm as opposed to 130) or trying to do both with only one product.


Shimano Dura Ace FC7900 crankset with 11 speed group? I have a Dura ace FC7900 crankset and was wondering If I can use it on a bicycle with ultegra 11 speed group?

The crankset I have is this one:
http://www.bike-discount.de/en/buy/shimano-dura-ace-crankset-fc-7900-53-39-170mm-31545

Thanks

The FC7900 crankset is from a 10 speed group.

Nobody's going to stop you from doing this and having it work -- Zinn has done it and claims that it works. Manufacturers will will say otherwise claiming weaker FD springs or very slightly different chainring spacing.

Since you already have the crankset, may as well put it in and try it if you want to use it.


Di2 front ring drop down when going uphill Di2 ultegra front ring drop down when going uphill. No pressure is applied on shifters.  System works just fine on flat sections. What could be a problem?

The general reason it might drop when climbing but not the rest of the time is that one of the jobs done by the front derailleur is keeping the chain from falling off by having the inner cage positioned suitably close to restrain it. Flex in the frame, crank, and/or chainring can widen this distance. There are instances where secondary chain drop prevention devices need to be used to eliminate or minimize drop no matter how you adjust the derailleur. Note that none of the above is different between Di2 and any other front derailleur.

Presuming you're indicating the problem occurs when in the small ring, any of the installation and adjustment parameters except the high limit adjustment and trim adjustment could cause or exacerbate this. Depending on whether you've got a braze-on or band type model, these include the mounting height, support bolt engagement, clamp angle if applicable, and presence and/or correct positioning of the backup plate if applicable.

As far as this problem is concerned, the only differentiating factor with it being Di2 is that all Di2 front derailleurs have support bolts and only some non-Di2 ones do. The support bolt is partially responsible for setting the angle of the derailleur cage, which if incorrect will widen the gap between the cage and chain in the area adjacent to the chain when in the small ring, which in turn can be a cause of your problem. So that and the state of the backup plate (aka frame protector in Shimano parlance) is a good thing to check first. The plates can fall off, which is a very good thing to catch sooner than later, and which could also cause this problem to start all of a sudden.

Particularly if they're a band type or a braze-on type being used with an adapter, FDs with support bolts (and also trim adjustment in post-first-generation Di2's case) are more sensitive to being adjusted in a particular sequence than those without. The mounting angle and the support bolt engagement together determine the final angle of the cage, but there's a spec for how much the support bolt should be acting upon it. The inner limit needs to be adjusted after the correct angle has been established with the correct amount of support bolt engagement, and needs to be re-adjusted if either of the other parameters are changed, or if the height is changed. If your model has it, trim adjustment also needs to be re-adjusted after any and every mounting or cage angle position change.

With practice one learns their logic and can know whether, when, and how to go in and change just one parameter in isolation on these derailleurs, but until then it's much simpler to see them as procedurally adjusted and just follow the installation and adjustment steps in the dealer manual document for your model derailleur, which is available at si.shimano.com. When the sequence in the instructions is followed there's nothing too difficult about them, but if not it's easy to get lost. If that doesn't work, and there's nothing else like worn out drivetrain parts or poor chainline going on, then add a chain catcher.


Leaving a pedal in a cross threaded state I have a Kona Jake (specs here) with Shimano M520 pedals and I noticed that one of my pedals wasn't quite all the trough the crank arm compared to the other pedal, see images below:

The difference isn't much but I tried to tighten and then tried to remove the pedal (2nd image) but found it stuck.  Nearest I can tell, it's either cross threaded or some type of galvanized bonding took place.  However, my gut is leaning toward cross threading as I did use an anti-seize compound (Park Tool ASC-1) before originally installing the pedals.

My question is not on how to remove the pedal but the dangers or complications I might encounter if I leave the pedal as is. Please note, I don't have the problem with the pedal placement nor is there any play or free movement in the pedal at all.  And I am worried about prematurly damaging the crank arms if I force the pedal out.

It's also important to note that the pedals have been installed for just over a year at this point.  Also, when trying to remove the pedal I used a filzer pedal tool but didn't use penetraiting oil or anything like that.

So again, what are the dangers or complications I could encounter if I leave the pedal in it's current state?

Thank you kindly,

At this point the damage is done and the only options are to leave it as is or remove the pedal and heli-coil the crank arm. There are a few scenarios that can play out in this situation. The worst case is the pedal backs out unexpectedly, you loose control, crash and get hurt. I would think this unlikely as it has been like this for a year. I would use some Loctite 290 applied to the exposed end of the pedal axle. This type of product is a wicking compound. It will travel down the threads of the mounted pedal and lock it in place. If you are lucky the pedal won't back-out and it won't be an issue until the pedal or crank needs replacement. At that point the pedal threads are likely destroyed. If you decide to heli-coil the crank arm you could do it yourself, how ever the cost of the drill,tap and coils make it an expensive repair. It is likely more cost effective to have a local shop handle it.


bike routes around san francisco? I'm fairly new to San Francisco. I've taken up biking the last few months while I have been here, and I want to do a variety of rides around the city.  I am having no trouble making up my own, but I have been unable to find a good resource that has routes already mapped out.  If anyone has any websites they can point me to, that would be very helpful.

The San Francisco Bicycle Coalition has a SF Bike Map & Walking Guide that they'll give you if you join, or you can buy it at just about any bike shop in SF or online.  (and the online version at that link isn't bad).  It's got bicycle-friendly routes color-coded.  They also have various organized rides and other events.

SF Bike Coalition and 511.org worked together to make BikeMapper, a bicycle-specific tool for finding routes around SF.  (also available on SF Bike's site but set up a little differently.)

bicycling.511.org is generally a good resource. http://bicycling.511.org/maps.htm in particular.

Google Maps can give you bicycling directions anywhere, but is probably extra good in SF.

There's a bunch of different cycling clubs in or near SF, but I think many of their organized rides go outside of SF.  (SF is only 7 miles across).  If you just want to ride around on your own, you can probably find out the routes for some of these rides.

http://www.goldengatecyclists.org/ (based in SF)
http://www.dssf.org/ (LGBT and friends)
http://www.westernwheelers.org/main/ (based south of SF)
http://www.actc.org/
http://www.valleyspokesmen.org/
http://www.velogirls.com/ (women)


Recumbent with a shaft or other non-chain drive? One of the problems of a recumbent is the super-super long chain, often twice or three times as long as a standard chain. It's heavy, it's hard to adjust, it's dirty.

Are there any commercial recumbents** that ditch the chain for something else?

** I.e., not a youtube one-off experimental bike.

I've found a few mentions of bikes that made it to the rumor stage, but nothing in production. The best summary seems to be here:

  Disadvantages are:
  – high price due to need for special components
  – some loss of power when compared with a clean, well oiled chain
  – weight, that is about 1.5 kg more than a chain drive,
   (most of it caused by a heavy hub gear unit)

The core problem is that chain drives are ridiculously efficient, and bike riders care a lot about power losses. Even a cheap derailleur setup can get efficiency over 95%, and the gap between 95% and 90% is noticeable to most riders.

Note that the bike they're talking about there seems to have never made it into production - the web site is now dead. There's another "first shaft recumbent" from before that, also dead. Note that as with the all wheel drive trike when something unique breaks you have to make your own replacement parts if the manufacturer isn't around. That's not an issue for someone who's built their own bikes like Peter Eland, but for most riders it's going to mean living without that unique part.

There is a front wheel drive bike with modified hub gear that is currently (Jan 2017) available for pre-order, the KerVelo, but that bike is also heavy and aimed more at comfort than speed. Given the long history of ideas like this not making it into production I am skeptical that this one will.

A front wheel drive bike might be a better bet if you're really fussed by the long chain. Most faired speedbikes are FWD for the reasons you mention, but I suggest not trying to use that exact approach (the bikes are expensive and only work on straight roads with no wind). Those bikes exist, but generally are a small niche because they're tricky to ride. Flevobike and CruzBike are the two brands that spring to mind here. Cruzbike are still recovering from their start making awful conversion kits for uprights that never worked very well. Their from-scratch bikes might be better, I haven't ridden one. There is a dedicated community of FlevoBike enthusiasts out there. As always Atomic Zombie have their DIY take on that approach which might be a useful way to experiment with the idea.

As is so often the case, I built one and rode it enough to convince myself that I didn't want to go further than a very rough sketch. Well, ok, Megan built it and I helped:

The moving bottom bracket design makes drive very simple, at the cost of making riding more interesting. Back pedal brakes made it more tricky to get started than I expected, but at least it had brakes. With proper gearing they can be quite rideable.

Side note on design

Bicycles experience ridiculous torque at the bottom bracket. Mid-size car levels of torque (but at much lower rpm). That's why BB axles are such heavy, rigid parts. Extending that BB axle to become a shaft drive is tricky.

With shaft drives there are two broad options: have a thin, light shaft spinning fast, or a heavier shaft transmitting more torque at lower speed. The thinner, lighter shaft means gearing up a lot at the cranks, then down at the back wheel, and precision bearings to keep friction down for that shaft. But that long, thin shaft is fragile. Making it a bigger, hollow shaft is hard because you really want it inside the frame, or underneath it, and either option is mechanically complex and every gearing step adds friction.

It also needs to be completely enclosed because bearing seals would add too much friction. It can be done, but it's cheaper and easier to gear up less and have a stronger shaft spinning more slowly. Normally shafts are sealed but the enclosure means the shaft diameter has to be smaller than the enclosure, and since the total size is limited that means the higher torque option is required.

I have ridden a 2WD MTB with a flex shaft drive, and there was significant shaft wind-up under load. That meant that front wheel drive really only kicked in once the rear wheel slipped a bit which was disconcerting. There was also noticeable power loss from the flex shaft. The bike seems to have disappeared, so apparently other people didn't like it either.


What is the widest tyre that you can get away with, on a standard road bike? In general, what is the widest tyre that you can get away with, on a standard road bike (with dual pivot brakes)?

Edit: I have a Campagnolo Eurus wheelset.

With a bike designed around modern "short-reach" 39-49mm calipers, you're going to four main issues:

1) Brake clearance vertically.  If everything else is optimal, a 49mm reach caliper should be able to clear around a 32mm tire.  You can verify this with an unmounted brake.

2) Brake clearance horizontally.  Extra cable tension releases (e.g. in levers or inline) help with this, but the maximum width that the calipers can spread will not be enough to allow an inflated tire through, and even with a deflated tire you might have to force it.

3) Frame clearance. You'll need to have adequate clearance in three places: seatstay bridge, chainstay bridge, and fork crown.  In extremely aerodynamic frames, you also may have issues with seat tube clearance.

4) Rim width of your current wheelset.  The Campagnolo Eurus wheelset has a 15mm wide rim.  The general rule of thumb is that a tire should be no more than 1.45 to 2.0 times the rim width, which would limit you to roughly 30mm wide tires at the biggest.

In general 23mm should be expected, 25mm is likely, and 28mm is occasionally possible.  What actually works on a given short reach frame is going to be heavily dependent on the factors above.  Bikes with medium-reach (57mm) or long-reach brakes are more capable; I do road riding on a classic 27"-wheeled Trek refitted for 700c with long-reach brakes, 33.3mm tires and full fenders.


Press fit bottom bracket causing bearings to bind I have a carbon Cannondale mountain bike with what appears to be a PF30 or PF30A bottom bracket: two 6806 bearings pressed into cups, which are pressed in turn into the frame.

With the bearings and cups still in the frame, the NDS bearing feels slightly gritty and the DS bearing feels very gritty with high initial friction. So I'm thinking I need to replace one or both.

Except when I pull the DS bearing (comes out with the cup), it feels fine. Maybe 90% of ideal, no obvious grit even under pressure. Press the cup and bearing back into frame, though, and then it feels terrible again.

I assuming this is a frame tolerance issue: it's squeezing the bearing too much. If so, then replacing the bearing won't get me anywhere.

Does this sound like the right conclusion? The frame is still under the factory warranty.

What you're describing is common. One clue as to whether it's necessarily an issue depends on how a new bearing feels and lasts/performs. Press fits always take up some amount of internal clearance and so having some degree of what you describe on a worn bearing isn't necessarily a big deal. But if a new DS bearing behaves similarly, yes that's a problem.

To diagnose something like this, always take a bunch of measurements of the shell bore at different places to see if it's consistent or if the interference fit is greater than it should be. The PF30 standard is open and there's a technical paper for it out there somewhere that shows what these numbers should look like.

PF30 reamer/facers do exist and I daresay anyone selling cdale mtbs should have one. That should fix it better than new, although I don't know Cannondale's take on them on their carbon frames.


Continuing to use damaged cones in rear hub? I've read in many different places that if you take a hub apart and see damage on the cups, cones, or bearings (may god have mercy on you if your cups are damaged) That they must be replaced.

I recently bought a used bike that had a lot of miles on it. There was a tiny bit of damage on the cones in the rear hub, concentrated within about 1/8 of the race.

That seems to make sense: The wheel spun very freely, so it was well-tuned, and the top of the cones took very little wear. The damage developed where the rider's weight was: on the bottom 1/8 of the cone.

So I'm wondering if I can get away with simply rotating the axle so that the cones have the damaged side up, and the good side down. That way the damaged side will be supporting an insignificant amount of weight (and not messing the balls up), and my ball bearings will have the pressure on them while they're rolling over the good part of the cone.

Does that sound like a hack that will work?

No it would not work. The pitt didn't form just because it was on the bottom, the pitt formed either because the cone came loose, or an abrasive got into the bearings.

There's an equal amount of force being applied to the top of the cone as there is to the bottom when your hubs are properly adjusted. Think of the components in a hub as a stack, the cup is both the top and bottom of the stack, and the balls and cone are sandwiched in the middle, put some weight on the top of the stack and the force is going to be evenly distributed through everything. Your theory would only work if you left some play in the hub, which would only destroy the cones faster.

Replace the cones and balls, they're cheap, and I imagine that you don't want to have a reputation of being a hack mechanic.


Shimano R7020 shifter broken - no audible click when shifting I have had the shifters for about a year and they have only been used moderately on my road bike. I was changing gear prior to putting it on the turbo when the right long shift lever went 'slack'and it would not change gear any more when trying to move to easier gears on the rear cassette. It felt like the lever had reached the stop limit and there was no l,konger any audible click. Moving to harder gears with the small lever still worked fine.
At first I thought the cable may have snapped but this was still intact. After a lot of fiddling I decided to take the shifter off the bike completely. I then removed the rubber hood cover and the small cover plate on the underside of the shifter.
I took out the gear cable just to make sure it was not fouling anything up in the mechanism. I also gave it a good flush through with silicone spray as I know old grease and debris can cause problems.
Once clean I spent some time looking at the mechanism and found the following;

when the shifter is held upside down it seems to work properly and a small silver flange engages with the splined cog as you press the big lever across. It shifts up one gear at a time without problem and there is an audible click each time.

when the shifter is turned the right way up i.e as fitted on the bike, the small silver flange drops downwards slightly (as per photo-left of picture) and no longer engages the splined cog. The lever therefore just pushes right the way across instead of moving the gears one at a time. There is no audible click. I did try refitting the cover plate to see if this held the flange in place but no joy.

It seems like the silver flange should be under some kind of tension to hold it in place as gravity makes it fall downwards and away from the splined cog. I assumed maybe a small spring or something had broken. I therefore ordered a brand new shifter and found after fitting it to the bike the exact same thing happened.
Anyone else had the same problem or am I doing something wrong in the fitting process?
Photo attached showing silver flange on cog.

Thanks for the responses. Spent some more time looking at the problem and managed to solve it!
One end of the small spring seen in the centre of the picture fits through a small hole to keep it in place. This spring originally had no tension on it and seemed broken.
The other end of the spring had somehow slipped past the silver flange and was on the wrong side of it. This end of the spring has a small piece that should put pressure on the silver flange and only allows it to move slightly off the cog.
Once I had worked out how to get the spring in the right place it all works fine.
The way I did it was to pull the end visible out of the hole so the whole spring rotates. Find the other end of it and squeeze it past the silver flange so it rests on top. It is flexible so quite easy to do.
The larger end of the spring is then under tension and you can pull it back up and fit it through the hole. This is a bit fiddly but achievable.
Photo of the finished result with yellow arrow pointing to large end of spring going through hole and white arrow pointing to other smaller end resting on silver flange under tension.
Hopefully it may help somebody else. I wonder how many shifters have been discarded because of this small spring!


Sudden tyre deflation with no puncture At the start of my ride yesterday I was passing through town slowly and crossed a section of cobble stones (just a line running across the tarmac). I managed to hit the one cobble sticking out of the ground. I lost a lot of tire pressure (I normally ride 23mm tires with 90-95 psi, it dropped to around 20 psi) and thought I had gotten a pinch flat so turned back home to change tube. When I got home I tested the existing tube (in the bath tub) for holes and found nothing, I've put it back in the wheel now and reinflated, got through a 50 km ride yesterday evening and still inflated this morning...

Any ideas what happened? Is this a common (or at least not entirely unheard of) occurrence for others. The valve was closed and it's not the first time its happened to me either.

Here's the offending piece of cobblework, it's nothing extreme...

Three possibilities that I see

You did not suddenly lose air you just did not notice until you got to the cobble stone
The rubber tube failed and recovered
The valve failed and recovered

No so sure you had a sudden loss of air.  If the tire when from 90 psi to 20 psi in a short period of most likely you would have heard that.

Since the valved is the only mechanical device I going with valve failed and recovered. Either random or by force of the cobble stone the valve unseated and before it lost all air it re-seated.

I am definitely ruling out rubber tube failed and recovered.

If this has happened to you before on that tube then I would replace the valve or tube and valve.  If this has happened to you on more than one tube/valve then wow - it has never happened to me.

I agree with the comment a patch could fail and then recover at a lower pressure but if you were able to air it back up and hold I would rule that out.  My mountain bike was down to 20 psi once and tube only at low pressure could not find a leak but with tire on at 50 psi it did leak (at a patch).

See picture below. The little gasket may have deformed or it has a little slit that is held together with compression.  Another possibility is the the valve itself (not the knob) is not screwed all the way in.  Where you see the flat spot on the the threads screw that in with pliers.  I had a set of tubes that by unscrewing the pump some times the valve would unscrew so I would use a dab of thread lock.  I think that is actually a picture of a presta valve that the core does not remove - so screwing that in would do no good.


I want a bolt on crank, but dunno what terminology to use to find one I want to place a crank on a bike at a different location than the one the bike is originally located.
This is similar to what i want to do, this is an addon crank for a smaller person to pedal with a tandem bike sold as a kit. But the link is 404.

I want to buy this piece (black piece) it's a crank that can be bolted on but "bolt on crank" in google result in anything but. The image was found on Pinterest so that doesn't help me in finding this part.

TL;DR: The search terms to use may be "kidback adapter," "child stoker adapter," or "child stoker kit."

Googling for "tandem child bicycle crank" produced a link to Sheldon Brown's site, which had a page on tandems and children, and which had this to say:

For smaller children, (or larger tandems) a "kidback" attachment is needed. This consists of a "bottom bracket" that can clamp onto the seat tube of a conventional tandem, so that even a toddler can reach the pedals. Most tandem manufacturers offer kidback kits as an option, and there are also aftermarket units available from various sources.

The "bottom bracket" of a kidback is typically 1 1/2-2" forward of the seat tube, so it is best to move the stoker saddle as far forward as possible, either by reversing the saddle clamp if a "pipe" type seatpost is used, or by using one of the forward seatpost adaptors made for use with aerobars. In addition to improving the child stoker's leg angle, the forward saddle position reduces the reach to the rear handlebars.

An extra-long stoker stem is also called for with a kidback, preferably one that is adjustable for length. Many kidback users use drop type handlebars flipped over so that the child can hold onto the outside of the "drops". The U-shaped handlebars supplied with many small-wheel and children's bikes also can extend back to where the child can reach them.

A child as young as 2 1/2 can stoke a tandem with a kidback attachment, although only for relatively short rides. With time, growth and experience, your stokid will gradually be able to happily complete longer and longer rides.

A subsequent search for "kidback" showed, among others, a link to Rodriguez Bicycles, which sells tandems and these adaptors. There may be other companies selling them. This is just the first site I found, and I didn't search further. Note that per the FAQ, we strongly prefer not to make specific product recommendations. Also, kidback may have been Rodriguez's brand name, and a more general term may be "child stoker kit" or "child stoker adaptor". I would assume that many tandem manufacturers will offer these kits; Burley, when it offered tandems, seems to have done so (as described on Rodriguez Bicycles' site), Precision Tandems does (and the link goes to an installation guide), and Santana Tandems does also.
I see the question got at least one close vote, but sometimes, knowing what to Google for is not trivial, especially if you lack other specialized bicycle terminology.

Technical notes:
The stoker adapters clamp around your stoker seat tube, and they contain a bottom bracket inside. I don't know tandem terminology, but you do run a short length of chain from the child's crank to the actual stoker crank. Below is a photo of the actual stoker crank, taken from Ray Dobbins:

In purchasing one of these, you'd need to match the clamp's diameter to your seat tube diameter. It's probably worth reminding users to adhere to torque specifications here. The Precision Tandems link above shows the possible consequences. For steel tandems, particularly with thicker tubing, I'd assume it's harder to over-torque the clamp. I'd be more careful with lightweight racing tandems. Unfortunately, I have not come across suggested torque specifications. You could start with the torque specs for seatpost clamps, probably 4-8 Nm (but check if your tandem has a different spec). Given the expected power output of a small child, something in this range should be enough to secure the clamp.
I'm not sure what lengths kids' cranks come in, but I'm sure it's safe to assume a child stoker adapter kit would come with a crankset of appropriate length. Santana Tandems (link above) gives you a 125mm crankset. An alternative is that you can purchase crank shorteners and use an adult-sized crank. I'd assume a kit would come with a length of chain, but if you're buying a second hand kit, you might need to get a chain of more appropriate length to your setup.


How fast can my bike go? I have an old mountain bike and want to change to a Pashley style girlie bike. I use my bike to go to the shops, pop to places and go out and about with my dog running along side.  I find the seating position of my old bike very uncomfortable in all areas.  My concern is, Pashley style bikes only have a max of 7 gears and I currently have 21 gears, of which I only use maybe 4.  My speedo shows that I cruise between 5 - 15 mph on my old bike but I'm concerned how fast I can go on a bike with only 7 gears.  Is there any way of roughly working this out as I've not found a shop that will let you ride a bike at full speed before you buy it.  Thanks in advance, Sarah

There are various gearing calculators available on the web. Here is one of them: http://sheldonbrown.com/gears/

The top possible speed will depend on your gearing, wheel size, and max cadence. Of course, your ability to reach that theoretical top speed will be limited by your own strength and fitness.


Mount additional water bottle on bike frame with only one water bottle mount I only have one set of water bottle mount screws on my bike.  I would like to have an additional water bottle.  Ideally I would like to mount the bottle on the frame (preferably on the vertical tube).

Bonus: Can I order/build in Canada?

Get yourself two hose clamps that'll fit around the tube and some rubber strips to put under then so they don't scratch the paint up too badly. They'll hold a bottle cage on just fine.

If you can see under the dirt and grime, that's exactly how the bottle cage in this picture is mounted:

Edit: Here's another picture of a bottle cage mounted with hose clamps (not mine).


How to learn to ride a bike better? I can ride a bike somehow, but I'd like to learn to do it better (maneuvering, etc.) before starting to use it as a way to move about the city. Any suggestions how I should go about doing that, what I should consider? All I could find on the web was how to learn to ride for beginners.

The simple, short answer is practice. Simply riding around at moderate to slow speeds, practicing starting off, braking, stopping and negotiating tight turns will help build balance, confidence and control of the bike. Do this in a quiet spot away from people and cars if you can. If you are worried about falling do it on grass.

The most useful foundational bike handling skill is to learn how to stand up on the pedals, or at least take your weight off the saddle and onto the pedals through your legs. Being able to do this enables you to absorb bumps through your legs but also shift your weight around for better braking and low speed maneuvering. Being able to pedal while standing up also allows you to apply more power to get over short climbs or accelerate quickly.

Learning how to brake hard and stop quickly is obviously a very important safety skill. It involves using both the front and rear brakes in the right proportion  and shifting your weight backwards.

The other thing I'd recommend it learning how to use your bike's gears properly and be able to shift into appropriate low gears for hills, short steep climbs and stopping and starting.

Global Cycling Network has several bike handling skills videos. They are oriented towards fast road riding but the principles all apply. Here is their latest one:


Trying to identify headsets I need to replace the headset on my old trek 1.5 alpha 2011 model, and also my b'twin ultra 720AF will need the bearings replaced soonish.

Is there a reliable way to find out what headsets I need? I've had two close, but unsuccessful attempts at getting the right ones before. In the end I've had to give up and use my lbs, which is annoying as I have all the tools required to change these.

Any advice is most welcome.

I sent trek an email and they responded . They say the correct headset has article number 423140 and costs 29.99€


I need the help identifying what type of bike I have a notes specialized but that's about it Serial number M1Ei13897

Components:

Marzocchi bomber 03 exr comp fork shox
Guizzo carbon fiber oversized 31.8 handlebar
SRAM x-5 gears  specialized 1:1 ratio
Azonic Outlaw wheels with tubeless tires MTB also will
Tektro Auriga hydraulic discs
Cannondale handlebar grips
Raceface cranks

The frame is somewhat like a 2003 Specialized Hardrock, no later than that because the 2004 frames seem to have additional bracing between the NDS stays for the disc brake.
However, it looks like every single component has been changed or upgraded since. Therefore you answered your own question; you have a frame, a Specialized, with a list of components as you described.
See John Burgess' answer for a more precise match on frame i.d.


Are these chainrings the reason my chain skips/hops? When I ride my bike normally, then chain skips like crazy. I know it skips in the front because I stuck some paper in the chain to see if it moved and it didn't.

Chainrings:

The large chainring in the picture looks very worn out. Usually by the time teeth on a ring are "shark-toothed"- or very pointed- the chainring is completely shot. However, it's likely that unless you've been replacing your chain regularly that all the other drivetrain components (chain and cassette) have been worn beyond use as well.
You should get a chain gauge and a cassette gauge to check this, or go by your local bike shop as they should have both tools. Chain gauges are very reliable tools for measuring wear. Cassette/sprocket wear gauge measurements are usually to be taken with a grain of salt. If your chain is completely hosed you can bank on needing a new cassette as well. If it's worn out without being beyond expected tolerances for a worn chain, you might try replacing your big chainring and your chain and see if you get any skipping in the back. If you don't, good for you and enjoy your ride. If you do then replace the cassette as well.
Next time, before your chainring gets as worn out as it is, you can check chainring wear by visually inspecting "chain lift" off of the chainrings. This is especially useful when changing to a new chain on used chainrings. Chain lift is the amount the chain rises out of the dips in the chainring under torque. Hold your back brake, and while off the bike step on one pedal at a 3 oclock position. Look to see if the chain appears to be coming off the chainring. This will be a useful trick if you want to try to save your small chainring, which doesn't appear to be as worn out as your big one.
In the future, check your chain's wear monthly if your ride occasionally or weekly if your ride nonstop. Changing your chain when it needs it will increase the longevity of the other components that come in direct contact with the chain- most importantly your chainrings and cassette sprockets.


Am I better off buying a new bike, or upgrading my old bike? Half a year ago I started to use again my old Schwinn Woodlands MTB for commuting. I didn't want to spend a fortune on a new bike, I wasn't certain that I would like to bike commute daily.

Bike has kinda old equipment: screaming Shimano cantilever brakes and Shimano SIS derailleurs (48-38-28, 14-28). Steel wheels. Highest gear is too slow for me. However, the good old heavy CrMo frame is comfortable.

Since then I used the bike a lot mainly for commuting, touring. Now I'm at a crossroads. I'm thinking of buying a new bike (brand new or used) or re-equipping the old bike.  I would like better brakes and a bigger gear ratio on a workhorse.

If I buy a new bike, I would probably choose a new or used Merida Crossway 100D /Speeder/S-presso. I think a trekking bike would be better than MTB because of speed. I've tried a Crossway but at first it was strange, although I loved the big gear ratio and disc brakes.

If I would reequip my bike, I would use Shimano Alivio V brakes (maybe with red/blue Ritchey brake pads), derailleurs and shifters and 7-8 level sprockets. I also need to change wheels.

My dilemma is that is it worth to spend half price of a used bike to my old bike?  to reequip? Or is it better to sell it and buy another (new) bike. There are used bikes with quite acceptable prices.

2012 models are on sale nowadays, although I'm a bit skeptic that I really need a brand new bike.

What do you think?

As @Daniel said - I would suggest looking for a newer second hand bike closer to what you want. the cost of components, along with compatibility issues, will like make the exercise more expensive with a bike that has a few niggly problems that just won't go away.  However, it you are particularly attached to the frame, it might be worth while. Consider getting a donor bike, as whole bikes are usually significantly cheaper than the sum oft there parts.

If you go down the seconds hand or new path, Jamis (an I am sure others) make mid and high quality steel bikes (Look for the Dragon range in MTB) for those of us that appreciate the advantages of steel. At the highest end, the weight penalty is so small it can be ignored.

Edit :  List of steel road bikes


How to enlarge dropout slots? I have a Raleigh Grand Prix and was trying to put a modern wheelset on it, but the front dropout slots are too narrow to fit the axle. Is it safe or possible to enlarge the slots? The fork is chrome plated which I hear is very hard to grind.

In response to some comments, I'm moving from a nutted wheel to a quick release. Which is really weird to not have clearance for.

To be clear, I'm referring to the axle diameter not the hub width.

You can do it with files. The chrome does make the surface harder but it's not a big deal. This is usually seen when the fork was originally slotted to take a 5/16" axle. I'm not a Raleigh historian but I'd be a little surprised were that the case on a Grand Prix. It's also possible that it's a fork that fits a 9mm front axle very tightly, and you're trying to put in a 3/8" axle. (The difference is small enough that a lot of forks can do both.) If that's the case then the amount of material you'll need to remove per face is tiny, whereas going from 5/16" to 9mm is more work with a lot more care involved.
When I do this I use a flat bastard file to do the "slot" part, the two parallel surfaces. If you wanted to go nuts you could try to maintain the exact original alignment by using a caliper as you go on each slot to make sure you're taking an equal amount off both surfaces. What I do is give each surface alternating or the same number of strokes with my best attempt at the same amount of force until the axle just fits. This is way faster and as long as you're careful, I don't think you could screw up the wheel alignment too bad doing this.
Then you have to do the back of the slot, the curved part. The big trick to the whole thing is re-profiling that area without making it any deeper, or else the fork will lose alignment. You have to be very careful about this. In theory you can do it by taking a round file with the right diameter and working the whole area down, both sides at once. In practice using normal tapered round files I've always had a hard time getting that to work. I always wind up using a smaller round file, like a 6 or 8" bastard, and doing a kind of sweeping technique to get the profile right. It's an analog process and takes practice, and you could ruin the fork. Marking out all the material you want to remove beforehand is a good idea.


Probably Screwed up my Derailleur shifting from 1-6 without pedaling So I've had this problem for a couple months now, what happened was I was being stupid and seeing what would happen if I shifted 1-6 without pedaling... As a result, the shifting now is screwed... The bike will say 3rd gear but be in 5th (I don't think it will go to 6th). It only goes up to what it says is 3(actually 5) I can still go to first gear but it won't display any number because it already passed 1(which would be gear 3 I think). Also the chain has been slipping on the highest gear whenever I pedal faster or slower.. It seems to disengage for like 1/3 of a second and I lose my foothold on the pedals. Any advice? Any thoughts on what's wrong with the Derailleur?

Sounds like one of four possibilities.

1) Pulling on the shifter has bent the derailleur - very unlikely unless you're a gorilla or the derailleur was already bent/weak

2) Your gear cable outer is weak somewhere and the extra tension has caused it to collapse, which effectively makes the inner longer than it should be.

3) (was 2b) Your shifter was weak and has bent or the number indicator has moved/bent.

4) (was 3) Most likely, you've stretched or pulled the cable through the adjustment bolt on the derailleur mechanism.

Hang the bike up on a repair stand, or use rope/cable/something to lift the back wheel clear of the ground.  Use your hand to slowly pedal and pull the exposed gear inner wire with your other hand while pedalling.  The gears should change like normal, through the full range.  If this works, then the inner wire is too long and needs some slack pulled through the adjustment bolt on the derailleur.

See "four rear derailler adjustments" section at http://sheldonbrown.com/derailer-adjustment.html   for details on that.


Should I get a bike that's too small for me? I'm considering buying the 2010 model of the Pinarello FP2. They're substantially cheaper than this years model (~£700). However, they only have the 55cm frames in stock.

I'm 6ft tall, looking at this size chart it says the 55cm frame is suitable for people up to 5ft 9in.

Would it be advisable for me to get a bike of this size?

Is it going to cause me problems? Is it not such an issue? After all it's a massive saving but if the bikes unrideable (for whatever reason) then it's not worth it.

Riding a bike in the wrong size (either too small or too large) for long periods can lead to all kinds of lower back, upper back, neck and shoulder issues en various leg injuries, mostly in the knee. Also, your power output can be reduced significantly. So a properly sized bicycle is important.

However, "properly sized" really depends on the rider. Sheldon Brown has a lot of good info, but mostly it comes down to:

Try the bicycle to find out how it feels.
Compare it to your current bicycle.

Finally, you can compensate some sizing issues in this specific case with a longer stem and/or higher saddle. How this works also depends on the relative length of your legs and your upper body.


Tire went flat, then held air? During a recent ride my tire went flat on my tri bike. I was about to change the tube but thought I'd just put some air in the flat tire first. Amazingly it held air for the rest of my ride (another 2 hours). Why does this happen?

When I was a child I learned that with a flat you would first pump up the tube and wait overnight (if you had the time) before going through the effort of patching it.
As part of that pump-up action you would check the valve was tight.
Only if flat or soft again the next day we would spend the time and effort patching.
Very often it is indeed the valve which has a problem. Different types of valves can have different problems, in the ones we used there is a ring pushing the actual valve in position and it is rather likely for that ring to be less than tight. And those valves we used when I was a child had a bit of rubber tube, which often failed, so it was not uncommon to take the valve out and replace that tube. These days I often replace the current valve with a new one, just to make sure.
Other kinds of valve have a different system of closure and those are really likely to be tightened properly when you finish pumping or may re-set themselves when the tube comes to full power.
Slow leaks are often slow enough to hold air for quite a while. Do check the outside of the tire if you want to keep riding after a flat, as if a sharp item is logged in the tire, it will make for a much worse set of holes in the tube. There are different approaches. If you will replace the tube anyhow, you may want to leave the hole-maker in, to plug the hole. But if you need to patch the tube, do not ride any farther with a sharp in the tire.
I own a bike cart which has been allowed to have a slow leak for more than a decade, more likely closer to 25 years, as the loss of air was so slow that we would never be surprised by a flat while underway. I have now a new tube for it, as it is now no longer a slow leak, it was flat in about 10 minutes. (But I have to admit that I have not checked the valve yet.)
So yes, if you have the time, first just pump (and check/properly close the valve) when you have a flat.


Pros and cons of long and short derailleur cage? I'm thinking of buying a new derailleur in the future, but I don't know what type of derailleur to buy, there's long and short cage derailleurs but is there any differences?

I'm not sure if this helps but I have a Shimano Dyna 3x chainring that I recently converted to 1x, by that I mean I've removed the highest and lowest gear. The current drivetrain I'm using has 32 teeth.

Cage length is part of the derailleur design that determines it's total capacity - the ability to take up chain slack when shifting onto small sprockets or chainrings.

If you look at the Shimano rear derailleur specs page you will see that the the 'GS' medium cage models have a higher total capacity than the 'SGS' long cage models. Long cage models are generally for triple chainring setups or cassettes with very large sprocket size spreads.

When looking at a replacement derailleur you need to look at the total capacity and the largest rear sprocket supported. The total capacity needs to be equal to or more than: (difference in tooth count largest and smallest sprockets) + (difference in tooth count largest and smallest chainrings).

It's best to pick the shortest derailleur that meets your needs, the shorter cage has more leverage and tensions the chain better. They also have a lower profile and are less likely to hit branches or rocks or other obstructions on the trail.


Bike accessory: what is this for? I’ve been given this bike since it wasn’t used. It has this thing attached to the frame on the rear wheel. Does anyone know what it is for?

It's a bracket for holding an old style light like these

Photo from Amazon


Cateye Computer Probe Wire Repair I snagged the wire on my Cateye Mity 8 computer on the rack the other day and broke it mid wire.  I'm going to fix it by splicing them back together.  I'm worried about effects of getting the wires crossed.  I'm going to take some care not to cross them, but if I do, will it cause problems?  What readings should I get from it with a multi-meter?

There are a few ways you can do the magnet sensing:

Reed switch (a switch which physically closes with a magnetic field). If you swap the two wires, the sensor will work fine (i.e. it doesn't matter). You can test for this using the continuity tester mode of your multimeter (you'll have continuity if the magnet is near the sensor, and open circuit with the magnet far away).
Hall effect sensor (Generally, there are 3 wires on here: Vdd, ground and the output of the sensor). There are 3!=6 ways you can wire it (so 5 ways to mess it up). Most likely, you won't get a reading from the sensor until you get it right if you don't hook it up correctly. As noted by Chris H, if you have a Hall effect sensor, chances are the wires will be color coded so you'll figure out Vdd and ground, and the remainder is output. Your multimeter won't really help you here.
An inductor (basically, a coil of wire). If you swap the two wires, the sensor would work fine (it'd be equivalent to moving the sensor to the other side of the bike, i.e. it doesn't matter). Your multimeter will show continuity always, but if you have a LCR meter, you can check the inductance. If you measure resistance,  you should see a few ohms.

So, basically, if you have 2 wires, chances are you can swap them without worrying and the thing should work. If you have 3, maybe you'll have to disassemble the sensor, figure out which sensor is in there and then look up the pinout (or guess based on color coding of the wires).

There are a few more types of magnetic switches, but they're unlikely to occur in this application.


Helmets with dedicated mounting system for lights, cameras etc.? I have came to the conclusion that headlights work much better for me for cycling than handlebar-mounted lights. This is because:

A headlamp illuminates where one is looking, not where the bike is turning towards.
The angle under which the light falls on the trail is much improved. When handlebar-mounted light illuminates the trail, the holes and irregularities look bottomless, making it difficult to select a safe line.

Suppose I am considering buying a full-face helmet. Are there models, that are explicitly designed to have a light attached to them. I imagine some kind of rails on the side or in front or on the top.
Bonus question 1: recommended way to mount a conventional headlamp (one which people put on their heads) to a conventional helmet (skateboard-type or full-face)?
Bonus question 2: any lights, that are supposed to be mounted on the helmet, but their power supply to reside in the backpack?

The only helmets with built-in light mounts I know of are by Bell, which can mount the Blackburn Flea. I don't know if any of them are full-face. The Flea is pretty useless for offroad riding, it's too dim.

Lights usually mount up with velcro straps through the vents. When I was racing my MTB after dark Ay-Ups were common - small, extremely bright, and a remote battery pack that can be put somewhere comfortable. Not cheap though. Most lights with separate battery packs should be able to mount to a helmet. Check out Bikeradar or something for options.


What are good vegan diet resources for bicyclists? I am a vegetarian, and I bike 100-150 miles a week. I see that many cyclists are vegans, and I would love to try a vegan diet compatible with the high energy input that cycling requires.

Can you suggest books, websites and other resources which provide information on healthy and efficient vegan diets for cyclists?

I don't think there's anything particularly unique to your situation to warrant specific diet recommendations. Eat carbs while on the bike, eat what your body feels like when you're off the bike.

You're not self-reporting any actual issues you're having like feeling weak or tired, or having trouble achieving weight goals (e.g., gaining, losing, or maintaining) or fitness goals. So what makes you feel compelled to change something?


Can I use a 3x10 or 2x11 front derailleur on a 3x11 drivetrain? I recently started changing the drivetrain on my Trail 6 (2020) and I wanted to jump to 3x11 from the 2x9 mixed Altus/Alivio it came as stock. My mistake was not paying attention to the type of pull my frame was built for, for the front derailleur: it's bottom pull.
I have all the components installed on the frame: 3x11 22-30-40 XT crankset, 22-40 11spd sprocket, 11spd XT chain with 138 links and 3x11 SLX Shifters. But the front derailleur had front pull which, sadly, cannot be used on the bike's frame. For the moment, I'm using the default 2/3x9 Altus front derailleur but, as you may assume, it's kinda bad (25% of the ratios cannot be used due to excessive chain rubbing and whatnot).
After extensive search, I've realized that there are no 3x11 front derailleurs with bottom or dual pull... only 2x11 or 3x10. Since i`m not gonna return the drivetrain (I've tested it for 2 days and it started showing signs of wear/tear, as is normal), my question is: can I reliably (or semi-reliably) use a 2x11 or 3x10 front derailleur with a 3x11 transmission? If yes, which of the two is more recommended?

In case someone else finds himself/herself in my shoes, here's how it all turned out for me... so, the previous FD was a 2x9 Shimano Altus and it still managed to move the chain from one chainring to another. Since there was no 3x11 option with a different type of pull, other than front, i took a chance and ordered a 3x10 Deore SLX. Besides the usual min-maxes which cause chain rubbing, i also have some chain rubbing when on the mid chainring with the 2 largest sprockets. Otherwise, shifting is good, 9/10 it happens without any delays or the chain getting stuck between gears. I am still observing the behavior of the whole setup but as far as front derailleur goes, 3x10 seems to have ~93% compatibility with a 3x11 drivetrain. Thank you all for your time and answers.


How do you tell what brand/make/model of bike I have? I have a bike I'm trying to sell because it's just been sitting in my basement. It looks as if someone primered it and the only thing I found was a serial number. Is there like a website I can look up more info on the bike using just that number?

The serial number on its own is basically useless. They're not like VINs on cars: there's no global database of them and they're not even guaranteed to be unique. Each manufacturer of frames uses whatever scheme they want, and the serial numbers are purely for their own stock control.

To identify the frame, you need to compare its appearance to frames whose manufacturer you know. However, unless there's something very distinctive about your particular frame, it's unlikely that anyone will manage to identify it. Most frames have nothing particularly special about them, and many are made in enormous factories in China that sell frames to whatever brand wants to buy.

If you've identified a small number of possible manufacturers, the format of the serial number might allow you to tell which of them is correct. But even then, it's something of a long shot.

See also, Why shouldn't I care what model/make/year my bicycle is?


How to reduce pedaling resistance I brought my hybrid bike to Evans Cycles recently to get the rear gear mech replaced after I broke it.

When I got the bike back, it was significantly harder to pedal. I tried moving my gears lower but even then the amount of effort required to maintain the bikes speed is higher than before, considerably, which is making my commute exhausting which it never was before.

I notice that it is harder to change the gears now on my bike - twisting the handle feels harder and the gears move very snappy. Could it be they have over tightened something? What do you think it could be?

Thanks!

I think the problem is with the bottom bracket. Sometimes, when the crank arms are removed, they can be put back really badly, thus causing the pedaling system to be very hard. Or some other times it's just the bottom bracket that needs to be replaced. Once I replaced my bottom bracket, the pedaling system was better than ever!


Should I be continually weighting the handlebars? When riding a non-technical flat or ascent, should the arms support some of the rider's weight?
I have noticed that even in those situations, I can freely let go of the bars and continue pedaling without shifting my weight - all the time being bent forward. Maybe this is because of my bike's geometry, my technique is wrong or this is just normal.
To answer the questions in the comments, I am not sitting up, nor am I strong. I feel as if 80% of my weight is on the saddle, 18% on the pedals (striving to make consistent circles) and 2% on the handlebars (there is some change in my posture when I let go the bars, but it's like 1cm at most). Flat pedals - haven't ridden clips for a while.

It appears that the stem has been replaced with 50mm shorter one, and the fork with 30mm longer one. With my saddle all the way up, the handlebars are still a little higher.
The question stands, however - is this (a) efficient and (b) healthy position for cycling level roads and climbs?

Yes, the arms should support some of a rider's weight.

However, outside of a hard effort, the hands should be light on the bars and the arms should be relaxed. I'm reminded of a brief quote from Wheelmen,

  "[Eddie] Borysewicz adjusted the [American] riders' bikes, taught them proper positioning, and described how to use their abdominal muscles to keep themselves steady on the bike and their hands light on the handlebars."

Making sure your hands and arms are loose helps to not only take pressure off your hands, but it also can help keep your shoulders and breathing more relaxed as well. Try riding with a tense upper body for a long period of time and you will see the difference.

Therefore, while it probably isn't feasible to do for long periods of time, you should be able to remove your hands from the bars while continuing in the same position you just were (leaning forward, but not sitting up).


Descending without braking: where's the sweet spot? This may get too math-heavy, but it seems that only a few variables are needed to estimate the optimum slope to descend without gaining/losing speed.

I looked around, but wasn't able to find anything directly relevant- just discussions about drag at high speed.

You are going at constant speed when the driving force from gravity Fg is equal to the drag (air resistance) Fd plus friction (rolling resistance) Ff:

Fg = Fd + Ff

When coasting down a hill, the driving force is the component of the gravitational force parallel to the road:

Fg = m g sin(a)

Here, a is the slope (angle with the horizontal), m is the mass of bike and rider, and g is the gravitational constant. Slopes on roads are often measured in percent, and for small angles sin(a) is equal to the slope in percent. e.g. for a slope of 10% (100m descent on 1km of road) sin(a) = 0.1.

Drag is proportional to the square of the velocity v, the projected frontal area A and a drag coefficient cd, and the density of air rho:

Fd = 1/2 rho v^2 cd A

The drag coefficient cd depends on the shape of the object - streamlined bodies have a low cd, but for a bicycle with rider I find approximately cd = 1 in Wikipedia. I'd estimate the frontal area of a cyclist to about 0.4m^2.

Friction (rolling resistance) is proportional to a coefficient cr and the normal force (the weight component perpendicular to the road) Fn = m g cos(a):

Ff = cr m g cos(a)

The coefficient of rolling resistance cr will depend on the bike (lubrication, tire pressure, surface roughness etc.). For car tires on concrete, Wikipedia gives cr=0.01, so the Ff would be about 10N. That's about a tenth of the driving force on a 10% slope (see above), but on a rough road surface it might well be much more.

So we end up with

m g sin(a) = Fg = Fd + Ff = 1/2 rho v^2 cd A + cr m g cos(a)

Solving this for v gives:

v^2 = 2 m g (sin(a) - cr cos(a) ) / (rho cd A)

Putting in g=10m/s^2, rho=1.2kg/m^3, cd=1, A=0.4m^2, and m=100kg (nice round number for rider and bike), I get

v = sqrt( sin(a)-cr cos(a) ) * 64 m/s

The rolling resistance cr essentially is like reducing the slope somewhat, so a slope of 10%=0.1 with cr=0.01 is the same as a slope of 9% on a perfectly rolling bike. So, for a slope of 10%, the sqrt becomes 0.3, and I get a speed of 19m/s = 70km/h

It's not unrealistic, but perhaps a bit faster than I would have expected. However, there are simplified assumptions, friction and rolling resistance is probably higher and cd and A have a big effect, they all depend on the bike and the rider.

From the drag equation you can see why the racing position is with the head down. This position decreases the frontal area A considerable, compared to an upright position, and it makes the body somewhat more streamlined (reduces cd). As the drag goes with the square of the velocity, this gets more important at higher speed.


How do I cycle up steep rocky ground? When mountain biking with my friends, we sometimes end up tackling a severe up hill over rocky ground.

I usually find I end up putting a foot down first. I'm not sure what's going wrong. Sometimes my back wheel spins and I lose power and stop, or my front wheel lifts up and I somehow lose balance and end up going off to one side.

What techniques can I use to get further up hill before I lose it?

Thanks.

Weight distribution is critical, and it is a bit of a fine balance, much like doing a track stand. I find that it is easiest to do this by staying seated and crouching towards the front of the bike. Standing on the pedals will tend to put your weight too far forward and make it difficult to achieve smooth power transfer to the wheels.

Smooth Power Transfer is another important aspect. Remember that your rear wheel only has a small amount of friction keeping it from slipping. What you are trying to do is keep the pressure on the pedals strong enough to keep you going up the hill, but not so strong as to make the wheel spin. Things that can help with this are:

Staying in a seated position
Concentrating on pedalling in smooth circles, rather than a in separate pushes from each foot
Using as high a gear as you can manage while still maintaining a reasonable cadence. If you are using your lowest granny gear, it is much easier for your legs to overpower the friction between the tyre and the ground.

Balance, working on your low speed balance by practicing track stands and the like will mean that you are less likely to need to put a foot down, and more likely to be able to recover from a brief "halt" in your progress.