Bike chain slips in a strange way I bought a new bike about a month ago. And it made a strange sound from the first ride , I thought the sound was because it was new and will disappear with time but it didn't. The sound is like a sudden collision of the chain with the gears and it lasts for about a second and happens when I am pedaling under pressure ( for example pedaling up hill ) so I filmed the rear part of the chain in slow mo.

Some important points:

the derailleurs are fully adjusted and the shifts work fine
I tried using WD 40 on the gears but didn't work
the rear derailleur hanger is not bent
the slip happens every about 5 minutes on straight roads and about every 30 seconds on uphills
At the point of the sound, the pedaling feels very easy for that second ( almost no resistance at all )

Thanks

You can see in the video how the teeth on the cassette rotate quickly at the moment it slips(at :05 seconds), while the spokes of the wheel actually stay slow, then jolt forwards to catch up. This means that the freewheel mechanism in the rear hub is failing to engage.

It's actually quite dangerous because as it gets worse it could cause you to lose control, fall off etc. in the worst case.

It shouldn't be like that on any bike, especially a brand new one. So take it back to the shop and have the freewheel, or freehub replaced (whichever type it is).


Bike brake bleed question so after bleeding my Tektro mineral oil brakes, the brakes appear to no longer be functional. when I depress the lever until it touches the handle bars. I am still able to spin the wheel. I think it wasn't a bad bleed as I feel as if I am applying a rather substantial amount of force to the lever. I am assuming the problem is mineral oil on the brake rotor/pads. I have already tried using an oven cleaner spray and soapy water to clean the rotor and changing the brake pads(to used ones) to no avail.

So my question is as follows: should I buy a brake cleaner and a set of new pads? or should I attempt to cut my losses and get the entire brake system replaced?

If you can pull the lever to the bars there something more wrong than rotor contamination.

I would guess air got in the system but you just did a bleed. I’d Check fluid level, try bleeding again.

You may also need to pump levers to move pads onto rotors if you pushed them back.


Front Mountain Bike Cable Disk Brake Is Too Snappy on First Pull When I grab my front disk brake for the first time on a ride after my bike has sat for a while it will buck me forward.  Once it bucks me it works great.  I have tried cleaning it with disc brake cleaner but I have not seen any improvement.  Any help is appreciated.

I  removed my brake pads and sprayed the pads and disk with some good cleaner and so far it has been a success.  Thanks for the help.


Keeping my ears warm while biking in the cold with a helmet Biking in the Northeast has become a challenge lately because of the cold; my ears freeze.

I can't wear a hat (because of my helmet) - I never actually tried, maybe I can.

Sometimes I'll put my hood on and then my helmet on top of that, it looks really weird. (Helmets look weird, hooded helmets are a whole new level of weird.)

I'm wondering if there are any other solutions.

I normally have a single Bluetooth earbud in one of my ears as well, not sure if that makes a difference.

Try searching for the term "ear band". They tend to be thin enough to comfortably wear under a helmet, and the good ones are fully wind-resistant, yet breathable.

If you have an open ventilation-style helmet, I recommend a helmet cover as well, which is a fabric sleeve that stretches over the top of the helmet which also significantly cuts wind passing through, and may be easier to use instead of a jacket hood (not to mention more streamlined). Install once per season.

Balaklavas or "dickies" are also good to protect the neck and shoulders, and there are also polar fleece neck warmers that may be more comfortable and can bunch up nicely under the back of the helmet.

Any quality of biking glasses/goggles are useful, too — look for ones with clear lenses — which will ensure your eyes don't get a full blast of cold directly.


How do I find the right size of bottom bracket? I have an old cup-and-cone system that I need to replace; for the sake of simplicity, I would like to replace it with a cartridge.  Alas, I have no idea how to figure out what dimensions of the cartridge to buy; ubelievably, the exact dimensions of most parts don't even seem to be available at the point of sale, at least not online.  This made me assume there were some sort of standardization to it, but if so I can't figure it out.

However, the last cartridge I bought (though the spindle length was within 2 mm) seemed a lot more wrong than 2 mm (I think the symmetry was wrong.)  All I know is this:

SCM
3UB

is written on the spindle, which is about 124 mm long; and on the cup was written: 1.37x24T.

I have a triple chainring.  Thanks.

It would still be helpful if you posted a photo, but I think I can answer without it!

The first major dimension of a bottom bracket is its width. If you have a metric ruler or tape, simply place it underneath the bottom bracket shell. There aren't a bunch of standards super close together so you'll easily get this one right. 68mm is really common and would make your project very easy to complete, but it's ok if it's different.

Like @Criggie said, the 1.37x24T measures the threading. Threads are the next most important dimension, and yours is standard English which is very easy to replace.

Like I said in a comment, your old spindle was probably asymmetrical, but new ones are typically symmetrical. To get your correct spindle length, you need to measure from the center of your spindle to the outer edge of the drive (or right) side. Double that number and you'll have the correct new spindle size. You'll probably want a pair of calipers for this, but the $5 ones at the hardware store are more than sufficient.

I did a quick google and your bottom bracket is probably a Sugino. All I did was type in "SCM 3UB bottom bracket" to get there. This is a Japanese part that is likely NJS spec'd (criteria for use in Japanese track racing) so it very well could have an ISO taper and not a JIS. See here from Sheldon to understand these terms. If your measurements are perfect and your crank won't slide on to the right place, this is the next culprit. If this BB is ISO, and your replacement BB was NJS, then your crank arm was probably about 4mm off from where it needed to be.

Did you already get the fixed cup out of the bottom bracket shell? If you didn't, I'd just take it to the LBS for help. They can do all of these measurements (including checking to see if it's NJS or ISO) for you, and that way you only buy one bottom bracket- the one that fits.

Good luck!


Why are my ENVE SES wheels rubbing on frame when Zipp 303 didn't? Same tyres The 25mm tires are rubbing and they didn't when I had Zipp 303 on Cannondale 2017 EVO.

Seems like every time I put any pressure or even turn, tyres rub the frame. I'm only 140lbs (63 kg) and this is my 3rd Cannondale EVO but never have had any issues until adding ENVE wheels.

I added the Enve last year. They didn't rub during the Cache Gran Fondo only started after I got home (Colorado).  They've never really rubbed, just started after Gran Fondo trip.  I'm using the same Continental Gator Skin tyres as I had on the earlier on Zipp 303 wheels.

Many rear wheels with high-profile rims lack lateral stiffness. The beefy rim itself may be stiff, but there may be too few, too thin spokes, possibly at too small angles. As a result, when you ride out of saddle the rim and tire may be moving sideways enough to rub the frame or brake pads.

Here's a very good article if you're interested in this in detail: Debunking Wheel Stiffness

Also, you're not alone with this problem with Enve SES wheels: ENVE SES 4.5 with ENVE hub => brake rub


Are Velomobiles street legal in the UK? I saw a question about velomobiles and recumbent bikes and I was wondering if they were street legal in the UK?

Can you ride one on a cycle path or would you have to stick to roads?

References: Bikehub - Cycling and the Law, Traffic Signs Regulations and General Directions 1994, Road Vehicles Lighting Regulations 1989

A velomobile or recumbent bike is covered by the same law as regular bicycles:

  "pedal cycle" means a unicycle, bicycle, tricycle, or cycle having four or more wheels, not being in any case mechanically propelled unless it is an electrically assisted pedal cycle of such class as is to be treated as not being a motor vehicle

So it's legal to use to ride one on the road in the UK.

Cycle paths are a bit more complicated as some legislation refers to "bicycles" and some to "pedal cycles", so it would depend on how many wheels you've got and what type of cycle path / cycle lane / cycle track you wanted to use.

If you want to use a velomobile or recumbent bike on the road between sunset and sunrise then you may have problems. To be legal you'd need 2 pedal reflectors on each pedal and these have to be clearly visible from the front and rear. The design of most velomobiles and recumbent bikes do not meet this requirement. This law is rarely (if ever) enforced, I think your main worry on this point is if you were involved in an accident then the other party might try to use your lack of reflectors to show negligence.

Note - If your velomobile or recumbent bike is electrically powered then there are additional regulations that must be complied with, but I think that's beyond the scope of the question.


Which freewheel/cassette for this bike? I was recently given a mountain bike for free, which I could fix for use by my husband. It is just missing the rear wheel and freewheel/cassette. As far as I can tell it would have been a 7 speed one,as there are seven gears on the handlebars (correct me if I am wrong) plus the three on the front crank.
Could anyone tell me how I would know if I need a freewheel or a cassette, or if it matters? For info:

26 inch 36 spoke wheel on front
Shimano SIS rear derailleur
Shimano altus front derailleur
SRAM twist shifters I think
it will just be used for laid back family rides
it is a Explor brand made in 2000

Everything needs cleaning but seems to work. It is a bit modern for me! My other bikes are all 70's and 80's so it will be fun to do something new. I have never done indexed gears before
Many thanks for any advice.
Gill

As you are starting from nothing, it doesn't matter whether you use a freewheel or a cassette. The 7 speed chains are the same regardless. I would look around for a secondhand wheel, as it will be much cheaper, and you'll want one that comes with cogs, tyre etc.
If you are lucky the chain isn't too worn, and it will just work. You may, perhaps, need to adjust the gears as the offset might be different


Chain shifting when back pedaling On my bike I found that when I backpedal, if the chain isnt perfectly straight, it is prone to shift to a more central gear. E.g would be if on the small chainring and the largest cog, backpedaling even a turn or two seems to result in a shift to the 2nd or 3rd cog. I came across a similar question which settled with the answer that it is due to the chainline, which I agree is not perfectly straight, but neither is it so bad that it is considered "cross chaining" and it works quite well in the forward direction.

Beyond just chainline, is it also an indicator of other issues? Chain wear? Cassette wear (I notice that some teeth are angled forward/away from the bike, and such teeth end up causing the shift)?

This is a second hand bike which is 5-10 years old. Running Tiagra 9 speed.

This is pretty much expected behavior.

When you're pedaling forward, the top half of the chain is pulled tight by the tension from your pedaling, and the lower half is held in tension by the derailleur.  The derailleur is also very close to the rear sprockets so it can guide the nicely-tensioned chain onto the proper gear.

When you pedal backwards, you pull on the bottom of the chain which pulls the derailleur forward.  That creates chain slack.  Some of that chain slack shows up on the top half of the chain as the chain links get dumped off the front chainring into space on the way backwards.  If you watch the chain closely when you pedal backwards, you can actually see the top of the chain go slack and flop around a bit.  So when you're pedaling backwards there's nothing on the top side to maintain tension.  A slack chain will flop around and there's nothing on the top side to guide where the chain lands on the rear gears.  So the loose flopping chain is free to go where it wants.

Derailleur-equipped bicycles are not designed to be pedaled backwards. Pedaling backwards is a great way to drop your chain, especially if you do it suddenly and hard.


Can this bike be saved from the rust? So, I'm buying a bike to use during a summer before I go back home. I found this bike that I'm interested in buying however it's extremely rusty. I'd like opinions on whether this is a DIY clean up, or if I'll have to spend a lot at a bike shop. I have 0 knowledge of bike repair/maintenance, so if it would involve anything more complicated than rubbing it down with some product/aluminum foil, I need to know. Thanks]1

Anything is fixable given time and effort and money.

You need to decide first whether the bike fits you, and will do the job.

Then decide if its safe - do the brakes work right?  Does it stop and go okay?    Are there and thick patches of rust?   Poking at any suspicious rust with a pen will show how deep it is.

Consumables need checking too - depending on its history and recent storage, you may be up for 4 new brake pads/blocks, 2 new tubes and 2 new tyres immediately.  Look for cracking in the tyres, whether it holds air at full pressure overnight, and how hardened the brake pads are.

Fenders/frames
If you want to fix the rust, you could simply paint over it, but that fix will last months at best.

Remove the rust physically by sanding or foil and then painting, and it will come back after a year or more.

The best fix is to chemically treat the rust with a rust killer like Phosphoric Acid, which converts the brown/red rust into a stable white or black iron oxide.  Then you sand it and paint over.  This should last the longest.

Rims
Much harder to deal with - because anything put on the braking surface will wear off quickly under braking.  Best technique here is to scratch the rust off using a brass brush, and then apply the phosphoric acid to treat the bits you missed.  Ideally do this with the tube and tyre off.  And mind your skin - this stuff is nasty.

Finally, based purely on the picture above, it looks like cosmetic surface rust.  So if this is the case, you're probably able to simply ride it as-is.  Bonus, makes the bike less attractive to a thief.


Why do deep section front wheels get pushed around in crosswinds? If a bike with a deep front wheel or a front diskwheel were to receive crosswinds with a 90 degree yaw angle handling would not be affected since the pressure would be equally distributed among the entire wheel.

So why does the wheel turn at lower yaw angles?

This front "wheel" seems to be designed to handle optimally in crosswinds at normal yaw angles. Maybe one day somebody can make adjustments to the fork to reproduce the same effect.

The answer to your title question is "moving air exerts a force on obstacles", and deep section front wheels have more area affected by side winds so there's more force.

In any crosswind there will be some side force that applies a turning torque on the front wheel of almost any bike (viz, zero rake bikes have been made, but they have less trail than is common today). The diagram below shows the normal design, somewhat exxaggerated as was the style in the 1960's:

(via the esteemed Dave Moulton whose post I got the image from contains an interesting discussion about why we have trail)

Note that the centre of drag/centre of the wheel is forward of the pivot axis. Thus, wind force from the side will tend to turn the wheel downwind, in the same direction that the wind is pushing the bike. So the rider will tend to stay upright, unless the turn makes them crash into something.

The bike you have pictured has the opposite design - as the wind pushes the bike and rider away, the drag behind the steering axis will turn the steering into the wind. I predict that in many cases the centre of mass will move downwind while the support moves upwind, resulting in a fall. But note that the front wheel design pictured is at best going to require clean, dry conditions to operate, and those are normally only found on indoor velodromes, making side winds a non-issue.

The OP asks about airfoil effects: More streamlined shapes can generate lateral forces due to airfoil effects, as often helping propel the bike as slowing it down - this is why speed records must be set in zero wind conditions.

Ignoring drag just for this example, the direction of the force from the wind is affected by movement for a streamlined shape, but not for a round shape. The apparent wind direction changes, but the vector components are still just movement + wind. But because drag is nonlinear the total drag force will be greater on the sum (that's why headwinds are so annoying), but the side force will not change by a huge amount.

The key point, though, is that the side force is still present regardless of the shape of the section. You could have a perfectly flat plane and it would still experience the side force.

And what matters to the rider is that the side force exists. Once you have that force, the above discussions of geometry applies. Where the force impacts and how that changes the balance and steering of the bike is what makes the wind hard to deal with. Whether there's a force-aft component to that force doesn't affect balance or handling.

It's definitely possible that turbulence from the fork will mean that there's less lateral force on the wheel behind the fork. But the more streamlined the fork the less true that will be. For the bike you've pictured above there is no effect at all, since the "fork" is merged into the trailing edge of the wheel. Instead that bike will have the opposite effect - there will be more lateral force on the rear of the wheel because there is so much more surface area behind the pivot axis of the wheel (the head tube).


Should I replace my disk brake calipers? I have a pair of Shimano Deore BR-M615s on my mountain bike with about 3,000 miles and 5 years on them. Lately I've noticed that both brakes have too long of "pull" before providing braking. That is, the distance from when I start to pull the lever to when the pads engage feels too long, perhaps 3/4s of an inch or so. The braking power after the pads are applied seems fine. I think the pads and rotors are within spec.
When I remove the wheel and pads, "exercise" the pistons, and clean/lube with mineral oil, the pistons are quite finicky. Sometimes only one moves, other times after some the fidgeting, only the other piston will move. One piston does not return all the way back into the caliper (perhaps 1/2 millimeter protrudes). Sometimes the pistons are cock-eyed, extending from the caliper at an angle. Sometimes I notice air bubbles in the lube oil between the pistons and the caliper. It's difficult to get both pistons extending evenly from the caliper. After some fidgeting, I can improve the "pull" distance, but as the pads wear I have to fidget more.
I am considering replacing the calipers with the BR-M6000, but wanted some input before pulling the trigger. What makes the most sense to try next? Overhaul the current brakes? New calipers? New levers, hoses, and calipers? Live with the fidgeting?

What you describe in the first part of your question is normal. Longer lever travel may indicate you need to bleed the brakes. Uneven caliper piston movement is caused by contamination of the piston seals with dirt.  Park Tool has a video about cleaning pistons and seals.
However this is bit more worrying:

Sometimes the pistons are cock-eyed, extending from the caliper at an angle. Sometimes I notice air bubbles in the lube oil between the pistons and the caliper.

The pistons should not be able to extend at an angle. That's not 'lube oil' between the pistons and caliper, it's the hydraulic fluid (mineral oil in Shimano's case) and you should not be seeing any of it getting past the seals (or leaking anywhere).
This makes me suspect that the seals are worn out. The Park Tool video I linked above shows how they work.
Seems to me that it should be possible to replace the seals in hydraulic brake calipers, but I've never heard of anyone doing it - someone will maybe add a comment about that.
I would not assume that calipers and levers from different groupsets are compatible. I tried looking this up in Shimano's compatibility information but inter-groupset caliper and lever compatibility is not listed for MTB groupsets.


Tire with no ETRTO/ISO size I'm contemplating replacing the tires on my mountain bike with smoother tires since I am rarely ever on anything other than paved surfaces. I read up on sizing and am aware of the xx-xxx ETRTO/ISO sizing that should be on the sidewall but I don't see it anywhere. Could only find inflation pressure range and some manufacturer's marks. They are Kenda. I could see K-816-015 on the front and K-816-027 on the rear. The tires have the basic size 26x2.1. The rim has RIGIDA 1.75 stamped on it. AFAIK everything on the bike is original (I've had it since new from 1994). Inner rim width is 21-22 mm.

Based on Sheldon Brown's site and also having googled Rigida 1.75 it seems to point my rim/tire being based on 559 mm bead seat diameter.

So, the questions am I right about 559 mm, and (2) for a smooth wall tire I was thinking of 1.75", but could I go to 1.5"?

Older tires may not have the ETRTO/ISO size markings. On your tires the '26x2.1' marking denotes rim diameter and tire width.

'26 inch' mountain bike tires have 559mm rim diameter.
2.1 inch is the nominal width.

With an 21-22mm inner rim width you could run a 1.5 inch / 38mm tire, but probably not much narrower.


My disc brake rotors have started to corrode. What can I do? For the last two weeks, I was using my bike heavily in rainy weather. I was cycling during rain for hours. Now I noticed that the discs of my disc brakes started to corrode. What can I do now? Should I just clean them? If yes, how?

Generally, it will go away if you apply the brakes a bit (it will be a bit noisy at first, but after a few applications it will look as good as new), since the rust is likely only on the surface (this is one way to tell if a car has been not driven for a few days - rust spots appear on the brake discs, but they'll go away after a short trip around town). Otherwise, if its more serious, you can  try light sanding with sand paper / steel wool / wire brush or something similar and then cleaning the rotor with isopropanol.

It goes without saying, but, don't get oil on the brake rotors while cleaning it.


What features of a mountain bike's geometry gives it different characteristics? When you see descriptions of mountain bikes they are usually described as XC, trail, enduro etc. and have different geometries based on what sort of category they fall into. What are the defining characteristics of the bikes and their geometries for the different categories of riding? What makes a trail bike a trail bike and not an XC bike for instance?

The shorter the distance between the bottom bracket and saddle lowers pedalling efficiency, but increases standover height which gives you more room to throw the bike around.  This feature gets more pronounced as the riding style the bike is designed for becomes more aggressive i.e. an enduro frame will sacrifice some pedalling efficiency for stability over very rough downhill terrain.
A longer top tube leans the rider forward centring the weight distribution more, this gives better stability in the air and over rough terrain, but causes the bike to feel a little less manoeuvrable because it's harder to pull the front up.
Shorter chainstays allow the front of the bike to pull up easier because the pedals are closer to the rear axle (the pivot point when pulling the front up).  Aggressive bikes that want the stability of the longer top tube often shorten the chainstays to keep the bike feeling more nimble.
A higher bottom bracket lifts the centre of gravity up making the bike more difficult to corner, but a low bike is a bike that scrapes rocks more...
A steeper head angle results in a more responsive, lighter feeling steering.

So to give an XC example:

A pure XC bike will have a large BB to saddle height to maximise pedal efficiency, therefore a low standover height, but this isn't too much of a sacrifice as an XC bike is not aimed at very rough terrain.
Often rather than a long top tube, they have a slightly shorter one and use a longer stem.  This keeps the weight forward so the front doesn't keep lifting when pedalling hard up hill, but keeps the steering feeling light (not always desirable...).
Longer chainstays for the same reason as above.
Steep headangle.

Whilst an enduro:

Will have a low BB to saddle height so it can be thrown around over very rough terrain.
A long top tube for the extra stability.  An enduro bike can't use the long stem trick to minimise the top tube length, because long stems make the steering feel 'overactive' which is horrible on rough terrain.
Short chainstays to mitigate the long tube.
Slightly slacker head angle because it makes the bike more stable when going downhill.

Most MTB frame styles have roughly the same BB height, as everyone wants a better cornering bike and it's difficult to pedal over rough terrain anyway.  The only exception I think of are pure downhilling frames, where a very low BB height is desired but to minimise pedal smashes, shorter crank lengths are the norm.

Headangles tend to quite steep on most MTB frames even on very different styles, for example XC and dirt jump frames have similar headtube angles.  Once again the notable exception are downhilling frames, which have very slack headangles; although this for improving stability when on steep descents (it's harder to go over the bars).

The above is an oversimplification.  In the real world the parts play off each other, and their characteristics will change as a bike moves through the rear travel (if it's got any of course).  Also the above are frame characteristics; the length of stem, width of the bars, length of cranks, height of forks, etc. all play their part in the overall feel just as much as the frame does.


Drivetrain 2x conversion to 1x I wish to know more about converting a 2x to a 1x, especially the Force AXS eTap group set.
I currently have a double chainring, but want to ditch the Front Derailleur and go to a single chainring. I have read about narrow-wide chainrings being necessary for single drivetrains, because it keeps the chain more secure on the ring.
However, I have found this single chainring ( Force AXS specific ) WITHOUT the narrow wide.
I have also found this Force AXS one, but WITH narrow-wide one.. (incl crankset)
So there must be a difference or advantage or disadvantage for the two options. What is my best pick here?
Don’t worry about the range.. I never rode my small ring in the last 2000 miles.

While I don't speak Dutch, the link you provided seems to be for a 46t outer ring from a 2x system. If you look closely enough at the photo you linked, you can also see "46/33T" etched on the ring: that's the smallest chainring option that standard Force AXS offers (Force AXS wide goes down to 43/30). You can see that more clearly in the photo below taken from this retailer. In addition, you can see the shift pins (two pairs of two silver pins, each pair separated by 180 degrees), and a black chain drop pin. All that gives the first ring away as a 2x chainring.

The narrow-wide teeth of 1x chainrings do really help keep the chain on. If you use the 2x chainring, you lose that protection. Back when I used to race cyclocross in the early or mid 2000s, I recall that many people would use 1x systems there without the benefit of narrow-wide chainrings - but we would either run chainguards on each side of a single ring, or else run an outer chainguard plus some sort of chain catcher on the inside. Cyclocross-style chainguards were just plates you mounted in place of the chainrings with some spacers. An ad hoc solution was to take a worn chainring and dremel the teeth off.
It does seem like on mountain bikes, chain guards might be accepted as either an alternative or a supplement to narrow-wide chainrings. It's an alternative if you're converting an old bike. Some MTB riders may add a chainguard to an existing 1x setup for extra security; this practice may originate on the gravity side of the discipline, and it may be tricking down to some enduro and XC cyclists. This style of chain guard is something like a front derailleur minus any shifting capability. You'd clamp it on like a regular front derailleur.
If you are determined, for whatever reason, to use the 46t 2x chainring, I would see a chain guard as mandatory. While I don't have personal experience, I'd imagine that even on a road bike, I would not trust a clutch RD alone to retain the chain. The clutch merely stops the RD cage from moving forward as the bike travels over rough terrain. That reduces the amount of chain bounce you get over rough terrain.


Netherlands: where to buy cheap bikes? (Police autions, cheapest towns) We are a french couple visiting the Netherlands (starting tomorrow) by bike. We have few questions:

are there specific places / city where we have better chances to find cheap bikes ? (except amsterdam, since without bike it will be too big to start with).
we heard about police bike auction but according to some website it seems reserved to the community or people whose bike was stollen, at least in Amsterdam and Hardenberg (which is understandable). Do you know if they is a website listing all the police auction dates (we can go anywhere in the Netherlands to buy the bikes)? We did try googleing this "Fietsenverkoop bij politie + city-name" (translate with google translate) but we didn't find any info except for the auction in Amsterdam, Hardenberg (where being french resident we can't go), and Groningen (the next auction is too late for us)? Are there other keywords we could use?
what should we do if we find a good bike (not suspiciously cheap and from a private person : we found out about marktplaatz) without any serial number on it (in France there is no identification number on bike so we don't do if it's mandatory in netherlands to have a serial number, or if all the bikes have one). Is there a way to ensure it's not stolen? Would a photo of the ID card + the address of the seller will be enough?
are bikes cheaper in Belgium ?

Thanks a lot for your help!

There are several places to avoid if you are looking for a cheap bike, and several places to seek.

First to avoid:

Generally bikes tend to be pricier / lower quality in all towns with a big university because demand is high and many bikes are "consumed" by the buyer. Lots of exchange students buy a bike and discard it after a year rather than resell it, and most other students use their bike untill it falls apart with as little maintenance as possible and discard the wreck. So you're less likely to find a good value bike here: Groningen, Enschede, Wageningen, Utrecht, Amsterdam, Nijmegen, Maastricht, Eindhoven, Tilburg, Delft, Leiden.
Regular bicycle shops (they usually charge a high markup for secondhand bikes).

What to seek out:

As a counterpoint to the point about university towns above: in many of these university towns you get people who collect the wrecks and combine them into working bikes that they sell for a nice price. You'll find these people through marktplaats and they offer reasonably priced bikes.
the "Kringloopwinkel" or "tweedehands winkel" in whichever town you select (second hand store). They are quite often the party that receives "left over" bikes from the police and bikes removed for being "in the way" (which I explained in my answer to your previous question)
www.marktplaats.nl (with an "s") is a good source of cheap secondhand bikes. There is no requirement for serial numbers on bikes though insurance companies sometimes require it. You should probably go with your gut feeling when going this route, I think legal sales are the norm there though. You can do two things to improve your odds of staying on the right side of the law:

Check other ads on marktplaats from the same seller, check how long they have been a user on marktplaats longtime users are less likely to be fraudulent.
Dutch police has a tool to find "suspect" sellers. Fill in the sellers' username and/or e-mail address there to check if "reports" have been filed about that user (bikes are in the category "overig").

As to your final question: I think the dutch market for secondhand bikes is very liquid and very large. My gut feeling tells me secondhand bikes will be better value in the Netherlands but I never tried buying a secondhand bike in Belgium.


134mm rear dropout spacing on Al frame My bike has an aluminium frame and I measured 134mm rear dropout spacing. The wheel it came with has 130mm OLD. The dropouts are quite a bit flexible, the QR pulls them in on tightening.
This is the wheel it came with as far as I remember. I am the first owner, but rear and front rims while looking very similar don't quite match. Cannot remember to have (had it) changed.

I am driving this bike for years and thousands of kilometers without breaking the dropout. After a recent need to replace the sprockets and discovering that even the 12-34 megarange freewheel is not available any more I decided to upgrade to freehubs and cassettes. Got a used 7-speed hyperglide wheel to match the measured 130mm OLD of my old wheel and transplanted a current 8/9 freehub onto it, staying at 130mm OLD.
Conversion is done for some time and drive quite a bit with it, but there remains a nagging thought:

134mm is a weird spacing, isn't it? I checked with bolts, the dropouts are parallel, unclamped, and they still look parallel clamped to 130mm.

Could this be a 135mm frame, set to less dropout spacing by long use of a 130mm OLD wheel?
And is 130mm OLD the way to go, here?

Before transplanting I tried putting in wider hub: pulling the dropouts slightly apart I was able to get it in.
The 130mm hub is easier to get in and out and I have been using such for years and miles.
On the other hand, 135mm is "closer" to 134mm and would allow for less dishing.

Your frame is most likely intended for 135mm spacing and measures 134mm either because of manufacturing tolerance or because it was bent by using too narrow hub. The angle difference between 130mm and 135mm hubs is about 0.4 degrees, which is not really visible to naked eye.

135mm would be the way to go, but there is no immediate danger from keeping using 130mm either.


Old Cannondale MTB. 2nd set of wheels. Orig wheel has 8 speed cassette...2nd set has a 7 speed. Need advice OK...need some advice. I have an old Cannondale with 8 speed Shimano XT drivetrain.  My current wheel has the appropriate Shimano 8 speed cassette.(13-26).

I bought an old Schwinn with the intention of using the 26" wheels to slap some street tires on it to use with my Cannondale from time to time.

The Schwinn wheel has a 7 speed cassette (or freewheel...not sure yet if it's a cassette).  I'd like the 2 sets to be interchangeable and I don't want to re-adjust my derailleur all the time. Do I need to bite the bullet and try to swap the 7 speed out for a matching 8 speed cassette or do you think this set up will be good enough?

I have started researching this and I apparently need special tools to remove the cassette and the hub may not even be compatible with an 8 speed. yikes.  Your advice is appreciated.

You do not want to run a 7 speed cassette with an 8 speed drivetrain. The sprocket spacing is not the same (5mm for 7, 4.8 for 8) so your indexing will be off, and you will run the risk of changing one gear too far and dropping the chain (no matter how careful you are, you will do this eventually).

If the Schwinn wheel is a freewheel type, you can't put an 8 speed cassette on it.

If the Schwinn wheel is a freehub type, you still have a problem. 7 speed freehub bodies (that the cassette fits onto) are narrower than those for 8 speed and above, and a 8 speed cassette will not fit (although apparently this can be hacked, see here https://www.sheldonbrown.com/k7.html#897).

Something else you want to do is check your frame's rear hub spacing, it's probably 135mm but the schwinn wheels may be 130.

If I were you I'd sell the Schwinn wheels and get a set of 8 speed compatible wheels to avoid the hassle of trying to make them fit.


Upgrading from a freewheel type to cassette type I'm kinda new for this, I am planning upgrade my bike from a freewheel type to a cassette type. How can I determine the cogs for the cassette type? My old bike has 8-speed freewheel cogs gears which range from 13T-28T.

You need same number of speeds, same cog spacing and freehub body splines splines. If you don't have any specific need to change the range, you can pick the same sizes. If you want to change the range, there are plenty of answers about that on this site.

For cog spacing and splines, there are two common ones for 8-speed: one for Campagnolo and other for Shimano and everything else. Unless you have a road bike with Campagnolo, you can just pick any 8-speed cassette that is not advertised as Campagnolo compatible.


What bike (carrying) racks are available for Pop-Up Campers? I've got a popup (tent) trailer and need to carry 6 bikes. I'd prefer not to put them on the roof of my van (the roof rack is rated to only 100 lbs and it's really high for lifting bikes onto).

So far I've found this one:
http://www.discountramps.com/pop-up-camper-bike-rack.htm

But I also saw a Do It Yourself design for one that is a lot simpler. It would be great to find a simpler less expensive one like that to purchase.

Add a second towball on the rear of the camper and fit a car bike rack for three bikes.    If your camper has a spare wheel here, then a wheel mount may also work.

Add another upstand of some description on the front of the camper for a duplicate setup, and put three bikes on the drawbar.  Noseweight should be about the same.
 or

Similar option is to run two towballs on the towing vehicle, like this

The other option is to put some bikes inside the camper before folding it, but there's often not a lot of space once its all folded down.


Basic chainset compatibility question I need to replace my chainset (42x34x22). Would a 42x32x22 be a compatible replacement?

Given that all other things, e.g. type/diameter of the axle, are the same, the difference of two teeth on the middle chainring do not present a problem.


My folding tire has kinks in it I just bought my first set of tires. They were of the folding type.
Even after unfolding and leaving them overnight they still had kinks in the bead. It is a bit unsightly but that isn't the issue. Do the kinks affect the way they should be installed?

This is completely normal for folding tires. They will settle into round shape when they are mounted and inflated for a while.

When installing the tires with kinks, they do slip away from rims more often than perfectly round tires. One way to avoid it is to keep the part that is already on the rim tight. There's no need to align the kinks to something, or anything like that.


Why is this ring used near the Crankset? I couldn't comprehend, why this ring is needed. Please refer the pictures. Its a road bike (I am not sure if it matters or not, so felt like mentioning it).

In my Bicycle, this ring usually comes out loose, Should I be worried and get it replaced?

Edit: Its an old bike, I have myself rode on this one for nearly a 3K miles so far, since I bought it from a person who had been using it. The model might go down to be roughly 7-8 years old. Nonetheless, I love this one.

P.S.: Pardon me for poor quality of the images.

You have an older pre-cartridge bottom bracket. The bottom bracket is the axle and bearing assembly for the crankset. Rather than sealed bearings it has either loose ball or caged bearings. While the bottom bracket is assembled  the cup is adjusted to the correct preload. Preload determines how much movement there is between the bearings and the axle. It should be adjusted so there is a minimum free-play but still spins freely. Once the adjustment is made the ring is tightened to hold the adjustable cup in the correct position.


Should I use a road bike or track bike on my rollers or trainer? I have a road bike with a triple, a track bike with a high gear ratio.  Which should I use on my trainer for use with training videos?  Should I use a geared bike, freewheel single speed or fixed gear?

The bike to use will depend on the reason for using the trainer. If your use of the trainer is for off season track training use the track bike, road racing  use the triple,etc. If you just want some saddle time, the triple will simulate all of them to an extent, you can select the gearing of the track bike,the fixie or the single and leave it there.


Where does aero wheels noise come from? One time I hear someone said, with satisfaction, that his aero wheels sound awesome. I wonder where does the noise come from, is it because you ride so fast the pushed air makes the noise or is it just noise of carbon fairing vibration?

Carbon wheels will have a different sound die to handling vibrations differently than aluminum. Has nothing to do with aerodynamics.


Does anyone have experience with Bottom Bracket Tap/Facing sets? I'm interested in recommending my boss get the workshop in which I work a bottom bracket tap and facing set.

As it's quite an investment it's important to me to know what you're getting for your money. Does anyone have any experience in this area? I'm a bit of a bike snob so have always leaned towards Park Tool on these matters; apparently Cyclus also make a very good unit. Appreciate any experience or feedback you fine people have.

Bottom Bracket Taps and Facing tools are an expensive and highly specialized tool. As a workshop, owning them and knowing when and how to use them properly, is one of the key signs of a professional shop.

Many new frames are moving to design without threads, but these tools will continue to be valuable for years to come.

These are the brands I'm familiar with, and recommend:

The Park Tool set is quality, and durable. For a set of taps and facing blades that will be durable, and also are likely to maintain compatibility with future similar tool sets from Park, it's hard to go wrong there.

The Campagnolo set has been the quality standard for shop use for 30 years at least. I know of one shop that's had theirs in continuous use for at least that long. You do pay for it, and the Campy tap set is a separate tool.

The Cylus Tap sets are excellent as well, although durability is yet to be proven. They are a more complicated machine, which allows a speedier, and very well done, job to be performed. It also allows for more things to break on their system. This is an impression I have only. I have not seen one fail. It does require a separate tool for english and italian BB's, and the parts are not interchangeable.

The VAR tool set is the original, the one that Park Tool based their original design on. It's simple, durable, and classic. The design allows purchase of an Italian thread set to be used with the English handles, and vice versa.

Hozan Tools makes an excellent tap set, but not facer currently.

All of these tools are excellent quality and have reasonable likelihood of replacement taps and facing cutters being available through the years. Campagnolo, and Park Tool are fairly certain to stand the test of time, and I'd recommend on of those two.


Bike type suggestion for packed limestone trails Where I live (Ontario, Canada), I am lucky enough to have access to a number of packed limestone trails (former railways). These are fairly flat and great for bicycling. They are mixed use, so sometimes they are very uneven - mostly from dried up horse tracks or farming machinery.

I am currently using a cheap supermarket bike; the ride is really bumpy and uncomfortable at times. I was thinking of upgrading to a proper mountain bike, but I am wondering if that would be overkill as the trails are pretty flat. Should I go with a bike with front suspension only, or both front and back? Any suggestions are appreciated.

I also have a hybrid bike (Specialized Sirius Sport) but the thin tires and clip-in pedals make it less than ideal for those trails and I feel like I am damaging it.

No need to a full suspesion - waste of good money on these trails, you need $2K to get one thats half decent - however if you have got $2.5K burning a hole in you pocket, full sus will be more comfortable.  A Hardtail MTB is built a little heavier than a hybrid, but in the end, I doubt very much it would make a difference.

What I would do is look at some cheap upgrades to your existing bike. Go to the biggest tires you can fit (Without going insane) 2" would be good - rim width and frame cleance need to be considered. No only comfort, you might want to consider a shock seat post. These are a often considered "poor mans softtail", but do not get the attention they deserve - they do take some of teh stress and shock loading off the frame and wheels. They are great for taking the small ( <25mm ) bumps on these kinds of trail while remaining seated.

If you decide to go for a new bike, a quailty steel hardtail MTB or hybrid would be my pick (unless you can afford carbon or titanium), with low travel shocks (80mm, no more than 100). A 29er (29" / 700C wheels) rolls better over the rough than 26" and are ideal for these kinds of trails


Why chains differ for 10x cassettes and 11x I have Shimano Ultegra 6700 10x, I want to change crankset only to R8000.

But found in internet that, I have to change the chain also because I have 10x cassette on rear wheel.

It became so interesting why chains depends on speed 11x or 10x Shimano?

Successive speed generations are for the most part able to be crammed in the same space by making the cogs closer together, and a narrower chain is needed to avoid rub.

You should use teeny chainring spacers instead. There are many questions here about this. Putting an 11s chain on will work badly with your front derailleur and cause laggy rear shifting.


Thread locking fluid on fixed cog I just recently got a single speed with a flipflop hub and got the bike shop to switch it to the fixed cog.  While riding around, the gear came loose on the back hub and almost flung me off so I had to bring it back to the shop to get them to tighten it.

Does anyone use any thread locking fluid on the rear wheel gear to keep it from slipping on the hub or will tension from the lockring keep it secure enough?

And if anyone has used thread locking fluid, did they have any problems getting a polymerization reaction to occur due to a low electrochemically in the hub/cog due it being made from aluminum or some other lightweight material?

If you have a fixed gear type hub, not a dual freewheel flip flop hub, and a lockring which is properly installed, there is no benefit to using threadlock on a fixie hub.

Thread lock works just fine on aluminum, although it tends to cause stripped fasteners because it requires more torque than most aluminum fasteners can handle. With a fixie lockring, though, there aren't enough threads (surface area) to really benefit from a threadlocker.


What is this BMX brand logo? I bought the a new bike at the local BMX shop but what brand is this logo? I don't have any idea.

I accidentally found the answer to this question by... listening to Judas Priest. Yep.
Here's a picture of Judas Priest "Painkiller" album cover:

You can see the exact same "double fork" imagery, which reminded me of this question I read months ago (it's actually a common logo they use, not just on that album cover).
It turns out a company named Amity did produce Judas Priest BMX frames. Here's that frame courtesy of VitalBMX:
https://www.vitalbmx.com/product/guide/Frames,7/Amity/Judas-Priest,4046
We can see part of the logo on the second picture (I haven't found a picture of that frame from the front):

This is further confirmed by that integrated seat post clamp hole, that we see on the question's full view of the bike. It's not that common of a setup, so this + the partial view of the logo above means it's pretty much certain that...
The frame is an Amity Judas Priest Frame


Changing sprocket sizes: will front derailleur still work? I have a hybrid, which for better or worse, I am going to use as my commuting and conditioning bike for the foreseeable future.  I am interested in changing the largest chain ring for an even larger one.  Will my current front derailleur still work? Are there other drive train issues I should be warned about?

My current setup: Gary Fisher Kaitai,  Shimano C102 front derailleur, 48/38/28 crank.

(I would also like some advice on how large to go on this.)

According to the Shimano Tech Doc it looks like 48 teeth is the maximum recommended size and 48/38/28 is the recommended chain ring combination.

The spec sheet also indicates that the maximum jump between rings is 10 teeth, so even if you could fit a bigger ring, you would have to replace the other two as well.

I believe the Kaitai normally comes with a standard 11-32 rear cassette.  Normally 11 is the smallest number of teeth that you will find, but Shimano makes a cassette model called Capreo that you may be able to find and use that goes as small as 9 teeth if you are trying to get a "bigger" gear.  The nine speed cassette ranges from 9-26T, so you trade the bigger gear on the low end for a gear that will be much harder to pedal up hills.


Dealing with rust on a steel frame I have a small spot of rust on the bottom side of my steel frame's top tube (Columbus Niobium tubing).  It's from abrasion during transport that I didn't notice until it was too late.  The spot is about 2cm x 2cm and most the worn area is white in colour (base coat or primer?) but there's a bit of rust forming in the center.

I'm not ready to get the frame totally repainted so what's the best way to get this patched up?

The best method for handling exterior frame rust depends on how much time you'd like to invest. The difference comes down to what you use to complete the two basic steps:

Remove the rust

Good: Sandpaper - Cheap, but wont remove all the rust, and may leave debris.
Better: Steel Wool - Will remove most of the rust, but may leave steel wool fragments, which can rust in turn.
Best: Brass Wool - Since brass will not 'rust' (oxidize) like steel, any fragments left behind won't cause the frame to rust.

Cover up the spot

Good: Nail or auto polish - Not technically the best sealant, also will wear faster and will need to be re-applied.
Better: Auto or spray paint, primer, or a clear lacquer - More water-tight, longer lasting.
Best: Bicycle paint - This is a given. =]

The most important point to note, though, is to remove as much of the rust as possible before painting. Simply painting over the rust will just seal it in, and allow it to continue rusting away beneath the layer of paint.


Disc Brakes VS cantilever / V brakes Are disc brakes better, more durable etc. than the more traditional Cantilever / V type brakes?

I have been considering choosing a new bike with disc brakes, but I have seen mixed reviews on whether or not they are really better or are just something that looks cool?

Thanks

Whether disc brakes are better or not, depends on what application you plan on using them for. Road bike? Mountain bike?

For mountain bike use and possibly even a commuter bike, yes, disc brakes will be much better. They can provide more power, better control and they can usually be easily modulated. They will almost always be better in rain and wet weather, which I think it one of the main advantages of using disc brakes.

On the other side of the coin, if this is your first time switching to a disc brake setup, then you will have something new to learn in terms of maintenance and brake adjustments. Of course, anything can be learned... Disc brakes will also weigh a bit more than traditional rim brakes.

Personally, I will always go with a bike with discs. Reason being, is that I know they will always work, no matter the conditions. They are reliable and provide the confidence that I need when I am riding a bike, whether on the road or on the trail.


Will using WD-40 to flush cable housing dirt harm the housing? I have a bike with a really old shift cable and housing. There is significant friction between the housing and cable.

I will replace the cable, but hesitating to replace the housing because I will have to make many cuts to new housing and do not have a housing cutter tool or a dremel. If I can reuse the old housing effectively, that would prevent me from making bad cuts.

Instead, I'd like to use WD-40 to flush any dirt/gunk that may be in the housing now.

My question is: After I do this, will the residue from WD-40 gunk up inside the cable? If so, what alternatives can I use to flush the housing?

I will have to make many cuts to new housing and do not have a housing cutter tool or a dremel. If I can reuse the old housing effectively, that would prevent me from making bad cuts.

Before I was able to afford/invest in a more suitable (i.e. less crushing) cutting tool I used to make do with common side-snip pliers; then doing my best to reform any squashed portion of the coiled housing so as to not obstruct the opening at the the end.

On top of this you also try to keep the face of the housing end as square as possible to the cable so it sits as neatly and unobtrusively against the barrel adjuster or cable stop at either end; minimising bend or creating a friction point.

Cut as short as lengths off as possible of course and use old waste lengths to do some practice cuts, knowing what you want to achieve.

It's doable; just a little bit more fiddly and irksome. I've been there.


Estimating FTP from Strava analysis I bought a power meter. I understand that you should do an FTP test to work out your threshold. But until I have time to do this, could I take a reasonable guess from a recent 35 mile road race?

These are the graphs from Strava, for the estimated distribution, it says average 230W. Is this a good starting point? Or should I go higher or lower, or should I ignore the graphs because Strave is just trying to guess it from speed/hr.

Edit - same course but ridden with power meter:

I raced the same course again, here are the same graphs from strava. It was a much windier day, and my finish time was just under 3 minutes slower than the last race.

You own a power meter - just fit it and go for a hard ride.

For others who don't own a power meter (and lets face it, they're not cheap)

Its a poor data point, but a chap at work has a power meter and he can compare this number with strava's estimated power.  We've compared ~three races and strava's number was high or low by up to 30%

So your 230W could be as low as 160W or as high as 300W.  Repeated tests will help narrow the range.

Another analogue solution is to ride hard for ~20 minutes to the point you can say words but not a whole sentence.  Then use Strava's estimator on that segment.  Repeat.

If you have a Heart Rate Monitor, try and hold your heart rate at around ~90-95% of your rated maximum, which is about 220-(your age in years)


Conversion to single speed: crankset specs? I picked up a cheap frame recently which came with bottom bracket, 3x speed chainring, crank arms and pedals, handlebars, forks, and front & rear rim brakes.
I've removed the chainring and right crank arm and I want to buy a new crankset but I'm not sure what specs I need to make note of when shopping for it. I know it's a square taper BB, but other than I don't know what else I should be looking out for.
What measurements and/or fittings should I have my eyes open for?

You'll obviously want to select the appropriate chainring size and crank arm length.
Cranks have a specific chainline (the nominal distance from the chain to the mid-line of the frame). The required chainline is affected by the spacing of the rear wheel dropouts, i.e. a 148mm spaced disc brake MTB frame has a wider chainline than a 130mm spaced rim brake road frame.
If you want to re-use the bottom bracket you'll need a crank with a square taper interface, however there is an annoying issue with matching cranks where the axle is built into the bottom bracket (i.e. '3-piece' crank/BBs: square taper, Octalink etc.): different crank models require a specific bottom bracket axle length to achieve the correct chainline.
Normally, if you can't find a crank that requires the same length axle you have, you'll need to replace the bottom bracket along with the crank. Often, replacing the bottom bracket opens up the possibility of upgrading to a '2-piece' crank with external threaded bottom bracket bearings such as the Shimano Hollowtech II system.
If you are converting a derailleur bike to a single speed (your question is a bit ambiguous as to whether you mean a proper single speed or 'one-by' with a single chainring a derailleur/cassette in the rear) then you can play around with the position of the sprocket on the freehub body to get good chain alignment and chainline isn't important.


Is having a disc brake on a single speed bicycle a bad idea? I talked to a bike shop that sells a lot of fixed/single speed bikes. I asked them if they could sell me a single speed with a disc brake on the front. The guys said no because:

It will be hard to find a frame that supports that
It is silly and not really needed and a waste of my money

If he is correct about the money part, then what would be a better place to put that money?

I bit of background: I commute year round, and I really like the stopping power i get on my mountain bike (with disc) during the winter / rain. I also tend to ride 20-25mph in Boston.

Well, there are lot's and lot's of commuter bikes with internal hubs and disk brakes. I see
no reason why a single speed wouldn't work as well.

A google search for "single speed cx bike disk brakes" turns up this beauty.

http://allcitycycles.com/bikes/nature_boy_disc

There are low budget models out there as well. Nashbar 29'r Single Speed

Swobo makes one, you can build a Surly Straggler up as a single speed.

Getting exactly what you want will likely cost a bit more, but that should be
for you to decide if it is worth it. If you're going to commute in the rain,
my opinion is that a disk brake is well worth the extra expense.

I'd go to a different bike shop.


I have a bike i wanna fix for my 2yr old grandson but have no ideas I want to make a monsters inc bike for him

Remove the crank and the chain. If possible the rear sprocket or at least cover it with a decent layer of tape or a bit of cut open rubber hose. Lower the saddle so he can put his feet on the ground and teach him to balance


Different tyre width (front and back) Out of necessity, I had to put an 1.26" (32mm) rear tyre on my bike where the front tyre is only 1.1" (28mm) wide (and the bike came with 1.1" tyres when I bought it). Are there any advantages or disadvantages of this, shall I try to get an 1.1" tyre for the rear wheel ASAP or is it safe this way?

Should be perfectly safe.  I actually did a similar thing on my road bike to allow a little more cushion in the rear, for my rear.  The only hassle I can see is if you have to carry two different tubes.  Can't remember off the top of my head if you can get some that span those two sizes.


How do treads affect traction? I've read that treads don't affect traction very much.  This is why NASCAR cars have smooth tires.

But, the road is not clean.  They say you can't hydroplane on a bike, but what about a thin patch of mud on the road?  Or spots with some gravel on them?

Everyone says treads don't matter for roads, but they still keep engineering road tires with treads, so I'm curious the degree of benefit that this really provides?

If you are riding on the road, you don't need treads. Even with mud. Even with sand, or gravel. Unless you are riding on the street in the middle of a volcanic mudslide or torrential rain washing out the road, it won't matter. The curved cross section of your tires coupled with your mass will instantly cut right through any patches of water or mud as you ride through. A bicycle under human power won't "rarely" hydroplane, it will never hydroplane.

You can slide if you ride over sand or fine gravel. The gravel can get between the rubber and road, and cause you to lose traction. However, having treaded tires will not save you. The layer of sand or gravel will be just as slippery to the treads. The treads can't cut through the sand or gravel, because the underlying road cannot deform. The treaded tires will just slide along the pavement, lubricated by the sand or gravel, just like a slick.

A behavior you didn't ask about, but you can encounter, is a squirming feeling, that you get if you ride an aggressively treaded tire on the road. This won't happen riding on dirt or sand, because the ground can deform. This squirming and deformation becomes especially troubling when cornering. The sudden transition from smooth to treaded in those silly combination tires, right during a hard corner, is especially nasty.

The reason companies make treads on pure road tires, like Blam suspects, is simply because the majority of bicycling customers don't think about these things in great detail, and think that their bike is just like a car with 2 wheels, and since their car tires have tread, so should their bike tires.

The takeaway principle is that conditions that will result in a loss of traction on the road, will do so regardless whether you have treads or not. Treads reduce the consistency of your tires surface, and in doing so, makes for a worse road tire.


Is there any difference between professionally painting a car and a bike frame? I'm getting ready to purchase a new bike which I love but I hate the color scheme.

I can't find any custom bike paint shops in the area. Can I simply take it to a car paint shop and get a professional team bike paint job? The frame is aluminum, the forks are carbon. Am I overlooking something?

You might want to talk to a motorcycle shop that does paint. They are most likely setup to do smaller parts with lots of details. They would be more familiar with masking threaded holes and bearing surfaces.


Monster-cross build on the road, will it be fun? Don't ask why, don't ask how much but this is what I'm aiming at:

29er entry level MTB with light Al frame stripped down
Carbon rigid MTB fork (for clearance)
Carbon drop-bar handle bars
35c tires
Road levers
Convert the 3x8 to 1x8 (46T x 11-42T)
Disc brakes

Since I've sold my road bike a year ago (after triathlons) I kinda missed the pure fast aerobic workout of a road bike but still have some gravel roads around me and wanted the versatility of CX/gravel to do some mellow XC around (for real off-road I'll use my friend's FS :) )

Gravel / CX market here is sooo pricy and I cannot get a good deal even on a used bike. So this beast would be way cheaper than that.

Me: 1.83m (~6'), weighs 95kg, Since I really liked the road bike aero position I thought about getting size M (17.5") as it will allow me to get low and forward on the handlebar.

My question is, would it be fun? would I go reasonably fast on paved roads? What do you think?

Thanks!

It will be a fun bike to ride, but it won't feel as fast as a road bike.

I've been building up variations of this bike for the last 15 years and there is simply no replacing the feel and acceleration of skinny tires and light wheels. Geometry also matters. Head angle, trail and wheelbase can be very far off the dimensions of a "normal" road bike.

Much of the "feel" of a road bike is not it's absolute top speed, but it's ability to accelerate quickly and be nimble in it's handling. Any changes you make in tire width and geometry will be compromises. The question that only you can answer is "Is it good enough?".

Tire choice will make a big difference in how fast the bike feels. Tires in the 35c range are all over the place in terms of weight, tread and rolling resistance. A light skinwall 35c tire with smooth tread can be reasonably fast and certainly makes bad roads and the occasional trip off the road's shoulder much easier. I really like having a bike that I can easily pull off into a dirt should and not worry about loosing control.


What is the correct way to put a helmet on? I hear often claims similar to "many cyclists wear their helmets the wrong way" and "wearing a helmet incorrectly significantly reduces it's protective ability".

My helmet is similar to the following one(only with vent holes). Note the two-stage straps on both sides (that is, one can tighten the helmet forward-up and backwards-up).

The manual featured a couple of crossed out pictures - don't tilt the helmet over your eyes (duh!) and don't tilt it so far back, that the forehead is bare.

I am in doubt if I am using my helmet correctly. What are the checkpoints to cover, before being positive that the helmet is not providing just a false sense of security?

For example, tightening. How tight should the helmet be? Must it resist grabbing it by hand and forcing it sideways around my head?

Another question of particular interest to me concerns the rear straps. Those seem to either hang (very) loose, or, if I tighten them and when I tilt my head (slightly) forward, stretch out and limit the movement (in an uncomfortable way).

The manual pretty much sums it up. The helmet should sit naturally at the correct place without the straps. The straps are only there to hold it in place in a prang, when a bit of chaffing / bruising  is the least of your problems.  A small amount of slack (you should be able to fit two - three fingers between the strap and you) is best. If the straps are pulling the helmet out of position, loosen them.

Be aware that not all of us have the same sized and shaped heads, so it is possible your helmet is just not a good fit.

Note also the bike helmet only protects against brain injury. Theres plenty of scope for a large amount of pain and cosmetic damage - think what a face plant at 30mph would do, and still scope for massive brain injury with a properly fitting helmet.

Its a reasonable argument that wearing a helmet provide a false sense of security - essentially if you would not do it without a helmet, don't do it.

Your helmet is a very last resort -  a "get out of jail" card that only works sometimes. Worth wearing? - I have a mate with a brain injury (non cycling) ... need I say more.....


microSHIFT on front gears, how does it work? Firstly, I do apologise if I don't get all the terminology correctly but I hope I'm still clear.

We bought a second-hand 18-speed bike that has a front gear system that I've not encountered before. It's called a 'microSHIFT' and it has a gradient whereby the rider needs to twist the shifter several times before a chain is moved onto a higher or a lower chainring. It's not just a matter of shifting from 1 to 2, there's several bars in between.

What is the purpose of this and how is it meant to be used correctly?

Microshift is a brand. They are Taiwan base.

Most of the twist shifter operates in similar manner as you described. They are for trimming as Batman said. But in fact it is made from the same machine and parts to keep the cost down.

It is all about how to set up the front derailleur in your system, and find a spot for each appropriate gearing. i.e. avoid chain rubbing on the front derailleur

There is one thing that I like about twist shifter, is that when you shift up, you can go slightly higher than where it suppose to be on the front chainring. This helps your chain to shift up easier and faster.


Retrofitting a roof rack A friend is willing to sell me at a friendly price the Thule roof rack pictured below.

It's home will be a Subaru Outback that already has the crossbars (see the blue rectangles above)

Any thoughts on how to securely attach the red-highlighted racks above to the cross-bars below?

I took @Christopher Hunter's comment above an an answer, thank you:  I looked up Thule adapter and found a retail shop near my house.  I visited that shop today and was told that adapting was not possible:  the rack attaches to the roof bar in two places ... I could purchase a back "tie-down" that was wide enough to span the roof bar, but not the front.

I ended up buying two rockymounts brand tierods.  I have not yet installed them and can return them in case someone believes I chose poorly.


How many times to patch a tube before dumping? Related: Patch or replace
  tube?

This video asserts that:

A properly patched area of a tube is stronger than intact tube area
Never patch a tube more than 3 times

Those are seemingly contradictory.

The video is just and example and motivation for this question. I have often seem people discard tubes with several patches, after they are punctured again.

Is it true that after some number of patches to a tube, it is better to dump the thing? How many?

My rule of thumb is the following:

Never patch a patch: when a puncture is too close to another patch so that the patches would overlap or almost, then I toss the tube
Never patch too close to the valve: the valve makes is a structural anomaly in the butyl that makes the tube, so is a more sensitive area, not to mention all the air input comes from there so it is a less stable area.
Toss a tube that has more than 8 patches... it is an arbitrary number but it is the one I set. Most of the times, when you reach that many patches, you will bump into one of the first two points,...

Of course, when in trouble, when you have no spare tube, and you have a flat, patch it no matter what. That is a no-brainer.

A properly patched area might be stronger than the intact area since it fixes the hole, but apart from the hole, it adds some thickness to the tube so puncture resistance.

You will (almost) never puncture a patched area: the patch might fail, but you will not puncture the patch.

That downside of the patch is that it does not expand (or just very little) compared to the intact tube (try to inflate a patched tube outside of the tire, you will see the diameter is smaller in patched areas). So an overly patched tube will be less expandable in the tire than an intact one.

This causes the whole physics of the tube inside a tire to be less perfect than it is conceived for; which is why you must not over-patch a tube (and solves the apparent contradiction).


Looking for cleats to match my vintage Mavic pedals Which type of current cleat would match these vintage Mavic pedals (Mavic 646 LMS SSC I believe)?

Thanks in advance.

I don't think those are the 646, but the cleat you probably still want to use is the Look Delta cleat. Go to a bike shop and try the delta cleat in there.

In the olden days, everyone was rebadging Look cleats as their own.
The 646 (and many old pedals) use Look Delta cleats (aka the original/traditional/ARC Look cleat; NOT the Keo cleat). The 646 should use the black cleat since it has float adjustment on it.

Picture of the Delta cleat (From REI):


Halfway through changing rear gear out cable I stupidly started changing the outer casing on my rear gear without having cable cutter ready. Suffice to say I've messed up the cut and now I can't get the gear cable though the outer casing. My friend is gonna give me his wire cutters tomorrow but I still need to ride the bike to work. Will this be bad for the bike to cycle without the gear being set up properly as long as I don't change gears when I cycle?

Thanks for your help

Yes, it's ok.

You'll be having the largestsmallest cog engaged, that's all. What you can temporarily do is set the limiting screws to the gear you wish.
Or you can have a short "pigtail" inner cable fixed somehow so it keeps the rear derailleur on the gear you wish.
Or you can take a punch or a small (Philips head) screwdriver, and a file and work the outer cable out.

Before purchasing the proper cable cutter I used to cut the outer cables with electric cable cutter, bringing it back to shape with a Philips head screwdriver and making it straight wit a table grinder. It gave a perfect result every time. Only the proper cable cutter is much faster.


How do you clip your helmet to your bag when not wearing it? I've been using a carabiner through the strap to clip my helmet to my backpack.  But it seems clumsy, and the helmet dangles around a lot.  I've seen other people with helmets closely mounted on a bag.  How do they do it?  Is there some kind of clip for this purpose?

You can make your own retention system for any bag which will hold the helmet secure and close to the bag. I've done this on a number of my bags as I carry both bicycle and climbing helmets at times and there is never enough space for them inside a bag as they're such awkward shapes.
Buy some elasticated cord (often called shock cord) and some cord locks of an appropriate size for the diameter of the shock cord you have. Threading this through a strap or some webbing on the bag and leaving the cord locks outermost will give you a size adjustable retaining loop that will hug the helmet to the bag.
Alternatively, find something (I've used shaped pieces of wood or plastic) that will fit lengthways through a vent on your helmet, but is too long to fit through the vent when rotated sideways. This becomes your toggle, tie this to the shock cord and you can use a single length (easier and neater to tuck away when not in use) with the toggle at the end. To fasten the helmet, push the toggle through a vent and twist it sideways so it can't fall back through the vent.
EDIT: a video demonstration and a couple of photos for you. Other manufacturers do this, Osprey and their 'lid lock' feature are just the one that came to mind for me to search out images.
a Youtube video of Osprey bag with 'lid lock' feature

(source: tri-sports.com)

(source: netdna-cdn.com)


Rides tracking app for windows phone What are some tracking apps for Windows phone which use OpenStreet Maps or Google Maps?
My location (Minsk, Belarus) is a white spot on HERE Nokia maps.

Windows Phones + Open street map

I know strava requires installation of the googlemaps app to function, but they don't make anything for windows. If you want to use their service of comparing against different users, you can upload data from another app as long as its the right format (which should be possible with any of those open street map apps for windows ).


Name for a part on stands/trainers So I am building my own trainer/stand for my bike but I am hung up on one part. What is the official term for the part that attaches to the hex bolt on the rear wheel?

In the manuals/parts lists I have seen, Schwinn and Blackburn refer to the part that envelopes the ends of the axle or quick-release skewer as a "cone". Minoura refers to it as a "grommet" at the end of a "coupling".

I don't have a Cyclops manual handy. I also don't think there is an industry standard name for this part, as there is some variation between all manufacturers when it comes to the coupling/mounting mechanism of their trainers.


Identifying Bottom Bracket on Merida Scultura 7000e I've just purchased a Merida Scultura 7000e frameset (unsure what year model). How do I go about identifying what bottom bracket standard it uses so that I can purchase one.
Inner Diameter of the bottom bracket hole is 37mm.
Depth of bottom bracket hole is about 9.5mm.
Trying to fit Shimano 105 5800 cranks on there (believe that they are cranks with a 24mm axle)

As per the documentation provided on Merida's website, the bottom bracket standard is PF86.
Source


Is cranking bigger gear from dead stop bad for your legs? So I don't have lots of money and just recently the bb on my vintage tube shifter 2x6 road bike broke and I have to make do with a slightly too long bb and mtb cranks because it's what I have.
Anyway before I can replace the bb and cranks, I'll have to make do with the big chain ring in the front (48) and the 4 heaviest gears at the back to prevent cross chaining. I find myself going usually on the two middle gears.
When stopping at a red light, I don't change gears, but just crank it up slowly while standing until I got to my desired cadence and then sit, though sometimes I got a little excited and sprinted away.
I've heard that climbing in too heavy gears can damage your legs, so is this practically the same? will I damage my legs doing it this way? I don't feel pain or anything, but just in case.

No, there is no inmediate danger to your knees. Most dangerous thing can happen is the chain snaps and you ram your knees on your tee, or frontflip over the bars while still.

Most Bmx riders use a equivalent cadence(I think this is the word) wheel to gear ratio, and almost every one rides standing up. Because part of the effort is made by gravity and your weight.

Just adjust the derailer in the front with the stop nuts and ditch the cable, so you can use your bike with a smaller sprocket. This is the poors man downhill chain guide.

byebye


Downgearing with a road triple My mother is trying to get back on her bike after years of knee problems + surgery, which so far has gone ok, but she has had some trouble with climbing hills. She's thinking that she should try to get some lower gearing on her bicycle. She currently has a "road triple" with a long cage derailer and a (relatively small, in my book) 11-26 tooth rear cassette.

I figured that with a long cage derailer, she should have plenty of flexibility in downgearing her cassette (with a new chain, of course). She took it to her local shop though, and they insisted that she couldn't downgear any more than to a 28 tooth cassette. When I called to ask about it, they said that even if she replaces her derailer, "with a triple it just won't work". I wasn't able to get more details, just a repeat response, even after I asked if the issue had anything to do with taking up chain slack or chain length on the large front + large back combo.

Every source I've found about the issue doesn't mention anything very triple dependent. Sheldon's site seems to think that shops are generally overly conservative on their downgearing recommendations, but that page seems to expect a bike with a double chainring.

What are the usual limiting factors on a downgearing conversion? What specific concerns should we have with a triple in front? How can I figure out how large a cassette I can get away with? And what ill effects can she expect if she violates the advice of the shop and puts a larger cassette on?

The triple is irrelevant. So long as the derailleur has enough capacity(which is determined by the size of the chainrings and cogs in the back; this is basically controlling how much chain length derailleur can keep tensioned) and largest cog ratings (for clearance ratings), you can put a bigger cassette.

There may be other ratings on the data sheet -- minimum cog rating, and maximum front chainring difference. These aren't really important. Exceeding the maximum front chainring difference may increase the chance of dropping the chain since the derailleur will need to take up some amount from a front shift.

The capacity is generally conservative -- if you don't use combinations like small-small, you can exceed whats written on the derailleur. Obviously, the derailleur needs to be matched for compatibility to the shifter.

That being said, you may also want to switch to smaller chainrings depending on the size of your chainrings.

Another item might be switching the type of bike your mom is riding -- if she has a regular road bike, a more relaxed geometry like a dutch bike may be more comfortable and ridable. Spending some time working out bike fit may also pay off, even with the existing bike.


Waterproof overshoes on Platform Pedals with pins Are there Overshoes designed to last on Platform Pedals with pins? How long would a "normal" overshoe last on platform pedals before it shreds?

Sofar I've been doing fine with some plastic and scotch tape but the appearance is atrocious.

You're right that most cycling shoe covers are made for clipless and only have a small cutout for the cleat. They'd get shredded by walking too much or using platform pedals. You could use hiking gaiters instead.

Alternatively, these delightful DIY shoe covers are open on the bottom, waterproof, and made with things found around the house.


Any chainless bikes in US I've had a Dynamic Tempo chainless bike for about 12 years,  but it finally broke down.  It looks like Dynamic Bikes is no longer in business (or at least the web page for them is not - transfers to Bike share).  Is there any chainless bikes sold in USA?  I have seen some in other countries.

I am guessing you're thinking of similar shaft-driven bicycles when you say "chainless", and those are indeed rare (although CeramicSpeed is working on a shaft-driven concept).  However, if you're looking for anything that doesn't have a chain, belt drive bikes are by far the most popular option, and are widely available from many different manufacturers including Specialized, Cannondale, and (previously, at least) Trek.  Ask at your local bike shop and the odds are very high that they'll either have at least one belt drive option in stock or will be able to order one for you fairly easily.


convert 9 speed wheel to 10 speed, won't shift to largest ring My Cervelo P2 has Dura Ace front/rear derailleurs, the ear wheel has Shimano 6600 10 speed cassette, it runs well.

Now I want to use a pair of old Corima carbon wheels. The rear wheel, a 4-spoke, has Shimano CS-HG70-9 9 speed cassette.

I did two experiments:

I put on the 9 speed carbon wheel directly, it seems to run well, chain can be shifted from smallest ring to largest without skipping a ring. 10 speed shifter misses 1 gear of course: shifting from the smallest ring to the largest, the first shift has no effect.
I replaced the cassette of 9 speed carbon wheel with Shimano 6600 10 speed cassette. I did some search, all say it's fine to put 10 speed cassette onto 9 speed hub. Put the wheel back on bike, the chain can only go from the smallest ring to second largest ring. 10 speed shifter misses 1 gear still: shifting from the smallest ring to the largest, the first shift has no effect.

Two questions:

Q1: can I just use the 9 speed carbon wheel on my 10 speed bike? will it cause damage to the chain set? I think the 10 speed chain is thinner, no?

Q2: how come I'm missing 1 speed after replacing the 9 speed carbon wheel with a 10 speed cassette? do i need to adjust the rear derailleur?

update:
I figured out the cause: when I moved the 10 speed cassette I left a 1mm spacer on the hub, as described here: http://www.bikeforums.net/bicycle-mechanics/781234-shimano-10-speed-cassette-washer-shim.html because of missing this 1mm spacer, the whole cassette is 1mm closer to the spokes, 1mm further from derailleur. as advised, I adjusted the rear derailleur and managed to get shifting back, but by putting that 1mm spacer back on, the derailleur is off again... though I wasted some time due to this rookie mistake, I actually learned a lot. thanks for all who helped

You probably need to adjust the 'top stop' screw on the rear mech, and also tighten the rear gear cable.  The rear mech has two small screws.  One of these adjusts how far up/inward the mech will move and the other screw adjusts how far down/outward it will move.  They are used to prevent the chain dropping off the top and bottom of the cassette.  Work out which one needs adjusted (trial and error should be ok) until the mech has the right range of movement to go from the biggest sprocket to the smallest sprocket (but no more).

Also, you might need to adjust the cable tension, esp if the mech is not moving from the smallest sprocket when you push the shifter.  You can do this normally by simply adjusting the screw mechanism where the cable attaches to the rear mech, and screwing it outward, so as to tighten the cable.  Again trial and error with this should work.  Putting the bike on a work stand where the rear wheel is suspended off the floor, and you can spin the pedals and wheels while shifting the gears makes this job much easier.  Dont be scared to experiment a bit to figure out how things work.


Unable To Adjust Mechanical Disc Brakes Properly I have a very puzzling problem with the front mechanical disc brakes on a big-box retailer mountain bike. Nothing fancy, and it used to work well for over a year but since I last dismantled it to clean it and eliminate squeal it's never quite worked properly.

Problem seems to be too much lever travel; when pulled tight I can get effective braking but released fully the brakes still stick. Letting out a bit more cable from the clamp will allow the wheel to spin freely on release but the brakes are almost useless even at max.

I've tried tightening and loosening the bolt in the caliper center but this doesn't seem to change anything (what does it do anyway?). Can someone advise how I can reduce the "range" of mechanical disk brakes or otherwise resolve this issue?

Mechanical disks almost always operate one side only. Setting them up correctly is not hard but needs care.

Refer http://www.parktool.com/blog/repair-help/avid-mechanical-disc-adjustment#article-section-3 for detailed instructions for Avids - technique should work for other brands.

Essentially, slack of the cable and caliper mounting bolts,  Undo both pads (counter clockwise) then tighten the outer pad 1/2 turn. Tighten the inner (non-cable side pad) until the disk is clamped tight and then tighten caliper bolts to set the caliper. Tighten the cable, loosen the inner pad 1/2 turn and outer 1/4 turn, then adjust as needed for modulation.

Although this sounds difficult and long winded, its actually only takes a few minutes once you get used to it.


SRAM Apex 1 doesn't upshift I have a Boardman CXR 8.9, everything stock except for new mech hanger.
It has a 11-42 cassette with a 11 speed 1x drivetrain. It's Sram Apex throughout, no mixing and matching like in other questions.

The issue is - while downshifting (going from smaller to larger cog) works well, the opposite needs a "nudge" most of the time. The "nudge" could be stopping to pedal for several seconds or pulling the shifter cable and then letting it go.

Already tried to fix my shifting, changed the mech hanger (original was slightly bent) but neither helped. Rear derailleur still seems sticky.
It seems that others had the same issue, but the only suggestion (use a spacer) doesn't seem to apply to me, as it's already there (see picture)

Did I miss something?

That sounds like a sticky shift cable.

Undo the cable from the derailleur, check the derailleur itself is not sticking. You can do this by getting the rear wheel off the ground, pedaling manually and pushing the derailleur body inwards to change down to lower gears, then letting it come back to higher gears. Be careful to avoid catching your fingers in the chain.

You could also do a quick check of the hanger alignment: from behind the derailleur sight down the chain. The cage should be parallel with the chainrings. This is difficult to do without the bike in a workstand, but you can get the same view by taking a picture with a phone.

Pull the shift cable out and wipe it down, you can also introduce a small drop of lube into the housing.

If that does not fix the issue consider repacking the housing and cable.


What tool is needed to adjust this headset on a children's bike? My daughter's bike has a threaded headset, and I don't know what tool I need to adjust it. As you can see from the picture, there are the following parts in the stack:

a knurled ring, which presumably isn't very tool-friendly
a ring (with a diameter of 35 or 36 mm) with three notches spaced equally apart (I'm not sure whether or not this is permanently attached to the knurled ring)
a standard six-sided nut, which I assume I can loosen and tighten with an ordinary crescent wrench

It looks like I'll need some sort of special tool for the ring with the three notches. What tool will I need for adjusting this headset?

The bottom ring is used to provide tension against the bearings to stop the headset from wobbling around. It only needs to be hand tight, hence no spanner/tool attachments.

The middle and top ring are tightened against each other, as a lock ring to prevent the bottom ring from loosening.

The top ring can be tightened with any spanner of the right size.

The middle ring requires a specialised spanner called a C-Spanner, a hook wrench or a hook spanner. It looks like the image below and is readily available from any bike shop or online store. Eg: Chain reaction sells one from Park tools


Does anyone recognize this titanium frame? I bought this titanium frame some time ago. No markings, only the serial number on the bottom bracket. The 84 probably stands for 1984 as the bike was fitted with Campy's 50th Anniversary gruppo. The BB is Italian threaded.
Any ideas?

This frame has some features in common with this Fracesco Moser frame I saw. But there are differences, as well: the chainstays, and the fork.


How to tell when to replace cassette? How do you tell when it's time to replace a cassette?
Are there any specific wear patterns on the teeth to watch for or symptoms specific to a worn-out cassette?

Without experience, or obvious damage, a cassette gauge like the one from Rohloff, or mileage are your best options for deciding when to replace a cassette. For me, a good rule of thumb has been:

10 chains = 2 cassettes = 1 set chain rings

That is, I change my chain every 1200-1500km. I change the cassette on the 5th time I change the chain. And I change the chain ring set every other time I change the cassette.

This is an example of an obviously worn chainring.

This is an example of a worn cassette.


Thinking of upgrading my brakes to these, is there an issue with "mushy" braking? I want to get these in combination with new levers for my bike, but under the description it says:

"Use of these calipers with standard SLR enabled STI and brake levers results in a "mushy" brake response"

I've got a simple, single-speed bike, I'm not sure how this will be an issue? All of the reviews seem great, and they're the only reasonably priced shimano brake calipers that are black to match my gear.

Maybe I'm missing the mark completely and these brakes aren't even meant for a bike like mine, if that's the case can anyone recommend some affordable brake calipers that I can upgrade to?

It's counterintuitive but brakes with a mushy feel are actually going to have more power. This is due to the difference in cable pull ratio. It also means you'll have to run the pad a little closer to the rim, which can be an issue if your wheels are out of true.
Overall, I think this would be a great setup. The new 105s are great brakes, and you'll have plenty of stopping power.


What saddle rail material is the strongest? I weigh about 120 kilos. Saddle rails bend.

I don't care about the weight of the saddle, just how strong the rails are and how comfy it is (I admire but have no desire to emulate people who cycle standing up. I have a bmi over 30, give me some credit for voluntarily cycling 20 miles a day)

As the diameter is standard (sort of) steel rails will be stronger than aluminium*.  But I'm surprised at saddle rails bending.  When I started cycling regularly I was about 100kg and even the roughest bits of road didn't come close to that kind of force.  You may benefit from a suspension saddle post for reasons of both comfort and damage avoidance.  Steel has a further advantage in that it's tougher than any of the other common materials for saddle rails, i.e. it can handle repeated stresses better without failing.

Do you ride very rough roads? If you get the occasional pothole or bump it's worth taking more of your weight on your feet just for a moment (you don't have to pedal while doing this assuming you don't have a fixed gear bike).

* Both carbon fibre and titanium saddle rails exist and are strong.  However they're usually used to make bikes light rather than strong and are unlikely to be available for anything other than road saddles (comfort was specified).m  Their brittle failure modes (carbon in particular) make them a bad choice in this case of unusally high stress.


Is it possible to estimate road grade while riding? It would be nice to be able to estimate the grade of a road while riding, even if the estimate is not completely accurate. With a GPS, in theory it should be possible in theory to ride a short distance and divide the difference in elevation by the distance ridden to get a rough estimate. (Note that the sine and tangent are comparable for small angles.)

Is the elevation given by a cell phone or GPS-equipped bike computer accurate enough to give a meaningful grade estimate over short distances? Furthermore, is there any practical way to estimate the grade of a road that does not require a GPS?

Get an inclinometer.  They're not particularly accurate, but readout is instant and the price is right.


What is the proper way to tighten dual bolt saddle rail clamp to stop rail slippage? I have a 2018 Specialized Allez, with Titanium 'Hollow Ti' saddle rails. To secure them to the seat post, there are two bolts opposite each other that both clamp down the same upper plate onto the lower plate that hold the rails in place. There is also a marking for 10 newton meters at the top of the seat post. My question is, is there a proper way to secure these bolts? (What I'm bearing in mind is that the upper plate is being affected by two different bolt tensions simultaneously).

I have had the saddle slip back during a ride twice now, only noticing when my position on the bike feels off, resulting in slightly scratched up saddle rails. I have also treated the 10nm rating as a maximum, and therefore usually tighten to 8nm for each bolt. Sometimes one feels a bit easy to turn while the other can feel like it is being forced, which is why I ask if there is a proper way to do this.

There is nothing applied like to the saddle rails (like grease) that might make it slip.

A good rule of thumb when tightening down any multiple fastener connection would be to finger tighten (if possible) each bolt until snug, them apply a tool and alternately tighten by stages slowly reaching the torque spec per bolt. This should provide a more even pressure distribution per side. NEVER fully torque one side while the other is loose, always alternate sides with even torque until THE SPECIFIED TORQUE IS REACHED. DO NOT UNDERTIGHEN, OR OVERTIGHEN. There is a little tolerance built-in to the spec (although possibly not shown (e.g. 10 Nm +/- 1 Nm). I do not have information on the hollow Ti rails, but I would think that they are engineered to handle the clamp pressure. You might reference the saddle manual to see if there is a recommended max torque the rails can handle. Due to shifting weight of the rider and slight flexing of the saddle during riding, I recommend that the torque be rechecked after the first couple of rides to ensure everything is still within specs and check that the saddle position has not shifted (I mark saddle rail orientation once comfortable, front-back and angle up/down to allow for easy verification/resetting).

Good Luck,
HPL


Why does my bicycle steer funny and feel unstable when I have a heavy load in my Bob Yak trailer? I have an Electra Townie 7D Tall which I use to pull my Bob Yak trailer. If I have say 30 lbs (16 kg) in it, my steering will be shaky and not feel very stable, especially at slow speeds.
Why and what can I do about it? I have used the trailer on other bikes with the same sensation.

I suspect Chris H is on the right track with his weight distribution question.
You may have too little weight on the front wheel. An easy way to test too little weight on the front wheel is by shifting your body weight forward when the bike feels unstable.
Experiment with the trailer load to find the best handling.
You may find that adding front panniers with some weight helps.
It's all about experimenting until you find the right distribution.
Looking for other people who are having problems with stability using a Bob Yak trailer has led me to some advice that might help.
In a thread on campfirecycling.com Jacob says:

I’ve been a bike messenger (in The Netherlands) for some time, using a Bob Yak professionally. Since my positive experiences with this handy one-wheeled-trailer I own one myself now, mainly for use as a vacation trailer.
When loading a Bob Yak/Ibex trailer you should keep a few things in mind. 1. Always distibute the load evenly along its length-axis 2. place the heaviest load nearest to the trailer’s wheel 3. When you overload a Bob trailer (which is fairly possible), never make the load ‘top heavy’.
I’ ve handled loads of over 50 kilograms with the Bob Yak and have had no stability or handling problems with it.
Tip: A bike without shockabsorbtion is most ideal (in terms of handling/control) for towing a one-wheeled-trailer like the Bob Yak.

Another problem some people had with the Bob Yak is high speed stability wobbles. cara2u posted this warning on forums.adventurecycling.org:

Please be very careful if you decide on a one wheel Bob. If they are not loaded correctly they can cause your bike to completely lose control
at the most inopportune time, downhill.
On our last TA tour we met an Aussie gal that had that very thing happen to her on a downhill. She was unconscious for two hours down in a drainage ditch until someone found her. She had to fly home to convalesce for two months before she could continue her tour. She was East to West and the accident happened the first week or so of her trip.

There is a lot more conversation about stability at speed in this thread.