Singlespeed & Fixed Gear - Quick release vs. bolt

I read somewhere that using a quick release was bad with single-speed bikes. This doesn't make sense to me, since the forces on the rear wheel should be the same regardless of whether or not you have a derailer.

But then the other day I totally mangled my derailer and had to do a quick conversion to single-speed to get home. The rear wheel slipped in the (horozontal) drop-outs two or three times, and I had to stop and realign it.

What gives? Someone enlighten me?

? because more force is directed across a cog in single speed mode than in derailleur mode as there are more teeth wrapped (ie contacted) by the chain?

i have a SS conversion like you and have to make the QR very tight on the back wheel. next hub will be bolted.

? because more force is directed across a cog in single speed mode than in derailleur mode as there are more teeth wrapped (ie contacted) by the chain?

i have a SS conversion like you and have to make the QR very tight on the back wheel. next hub will be bolted.

But that shouldn't matter, should it? A proper free-body diagram shows that the net force is still the same. The only difference I can see is that a derailer takes a marginal amount of the force off the cogs due to the springs (if that -- my brain hurts).

But it's weird. I rode that bike thousands of km's: sprints, hills, everything, and never had the wheel slip. Switch to single speed and it's sliding around like a drunk on an ice rink.

Then again, perhaps the original derailer fiasco was caused by a wheel slip and and not through derailer adjustment incompetence. Hmmm...

The danger is in power-start situations. On an SS or FG bike, you are sprinting away from standstill in a somewhat higher gear than you would on a geared bike (or if not, you're going to be spinning like mad). Also, on an FG, the reversal of forces, when you go from pedalling hard to resisting hard is something you don't get on a freewheel bike. I've got an SS with quick release, and I've never had a problem, but I don't think I'd run skewers on a fix. The only real problem I've had with slippage was riding a road bike with originally had 126 mm spacing, but somebody had fit a 9 speed rig, which meant that whilst it could be sprung into the frame easily enough, the dropouts were no longer parallel with each other. Had to tighten that thing down all to hell to get me across London.

You can tighten a 10mm bolt on axle much more than the 4mm or so nut end of a quick release. If you have ever messed around with hex or security bolt on skewers, you will know how easy they are to strip.

If you just have to run quick release, the classic chrome Shimano cam quick release has the highest clamping force you can get, and are all steel, so are much stronger than any bling aftermarket QR. Most shops have them in abundance in the junk bins of the workshop.

You can tighten a 10mm bolt on axle much more than the 4mm or so nut end of a quick release. If you have ever messed around with hex or security bolt on skewers, you will know how easy they are to strip.


That's not the question. Of course a nut can be made tighter.

But why does a wheel that doesn't slip with a derailer all of a sudden start slipping when made single-speed, all else being equal?

The danger is in power-start situations. On an SS or FG bike, you are sprinting away from standstill in a somewhat higher gear than you would on a geared bike (or if not, you're going to be spinning like mad). Also, on an FG, the reversal of forces, when you go from pedalling hard to resisting hard is something you don't get on a freewheel bike. I've got an SS with quick release, and I've never had a problem, but I don't think I'd run skewers on a fix. The only real problem I've had with slippage was riding a road bike with originally had 126 mm spacing, but somebody had fit a 9 speed rig, which meant that whilst it could be sprung into the frame easily enough, the dropouts were no longer parallel with each other. Had to tighten that thing down all to hell to get me across London.

1. The size of the cog is what matters, smaller means more force to put the same torque on the wheel. With a 16-18 you are likely to put a bit more force on the wheel when climbing and skidding but probably not starts.

2. there is no reversal of forces. There is a few degree change in the direction of them but not much.

That's not the question. Of course a nut can be made tighter.

But why does a wheel that doesn't slip with a derailer all of a sudden start slipping when made single-speed, all else being equal?

because all else in not equal. What cog did you set it too? Did you stand and mash more then when geared?

That's not the question. Of course a nut can be made tighter.

But why does a wheel that doesn't slip with a derailer all of a sudden start slipping when made single-speed, all else being equal?


Because, faced with a choice, the girlyman side of your brain takes over and clicks the shifter.

Without a choice, your riding is much more agressive and you use a lot more body english, pedal kicks, yomping to keep the bike moving.

You also tend to run a lower gear with single speeds, as acceleration is more important than top speed. The smaller your front ring, and the larger your cog, the greater the leverage. Sprinting out of the saddle in the big ring puts much less force on your axle than grinding up a hill in granny gear.

Combine these factors and the quick release clamping force is overcome.

Snap!

because all else in not equal. What cog did you set it too? Did you stand and mash more then when geared?

53-21 or so. Not sure on the 21, it was the third largest of an 8-speed Campy cassette. I'm sure I mashed some to get going, but I probably did when it was geared, too -- though I can't really say to what extent.

The more I think about it, though, the more I wonder if the wheel didn't slip to cause the derailer self-destruction (even though I was in low gear, I was mashing to get started up a hill from a dead stop). If it matters, the drop-outs are forged Campy, with Campy skewers.

I think tonight I'll go home and do the following test: Stand on my bike with the brakes locked and mash the bejeezus out of the pedals to see if I can get the wheel to slip. I'll report back. Or not.

1. The size of the cog is what matters, smaller means more force to put the same torque on the wheel. With a 16-18 you are likely to put a bit more force on the wheel when climbing and skidding but probably not starts.


Quite. I run a 42/15 setup, where I might more normally be starting in 42/17 away from lights or somewhere where hard acceleration is neccesary. This means that I'm torqueing the chain more, which is what would slide the axle forward in the dropouts. If anything, I'd guess this is what happened to the OP




2. there is no reversal of forces. There is a few degree change in the direction of them but not much.

In terms of pulling the wheel forward, you're right. I was thinking of the twisting effect on an axle which won't be as strong as a solid, but that's not relevant to the post here.

Quite. I run a 42/15 setup, where I might more normally be starting in 42/17 away from lights or somewhere where hard acceleration is neccesary. This means that I'm torqueing the chain more, which is what would slide the axle forward in the dropouts. If anything, I'd guess this is what happened to the OP

There is more force on the chain not torque. The torque on the wheel is not higher.





In terms of pulling the wheel forward, you're right. I was thinking of the twisting effect on an axle which won't be as strong as a solid, but that's not relevant to the post here.

If there is a significant twisting effect on the axle your bearings are ****ed.... really really ****ed.

Because, faced with a choice, the girlyman side of your brain takes over and clicks the shifter.

Ouch. Tough love.


Without a choice, your riding is much more agressive and you use a lot more body english, pedal kicks, yomping to keep the bike moving.

You also tend to run a lower gear with single speeds, as acceleration is more important than top speed. The smaller your front ring, and the larger your cog, the greater the leverage. Sprinting out of the saddle in the big ring puts much less force on your axle than grinding up a hill in granny gear.

Combine these factors and the quick release clamping force is overcome.

I was in 53-21, which shouldn't produce all that much chain tension.

But I hear what you're all saying -- mashing, yomping(?) -- I'm just surprised that the force would be that much higher. Time for some experiments.

Ouch. Tough love.



I was in 53-21, which shouldn't produce all that much chain tension.

yeah that shouldn't at all. Maybe you just didn't tighten the qr enough. They will slip with horizontal dropouts and gears too.

Yeah, 53-21 doesn't sound like it'd be a problem.

Yomping is pulling up on the bars at the same time as pedalling when you are out of the saddle. Old, old track term.

no matter what gear anyone here has on their bike they are never going to be able to generate the same amount of torque against that axle as a Pro rider can and they don't slip their QR so nobody here should be able to slip theirs.

I've been wondering the same thing. Why a bolt on an SS/FG and not a QR? What's the reasoning behind it? A bolt is much harder to loosen if you flat, so why is it being used? The OP could have had a problem other than a QR issue, so what about everyone else? What's the reasoning behind using a solid axle with bolts over a QR?

no matter what gear anyone here has on their bike they are never going to be able to generate the same amount of torque against that axle as a Pro rider can and they don't slip their QR so nobody here should be able to slip theirs.

I've been wondering the same thing. Why a bolt on an SS/FG and not a QR? What's the reasoning behind it? A bolt is much harder to loosen if you flat, so why is it being used? The OP could have had a problem other than a QR issue, so what about everyone else? What's the reasoning behind using a solid axle with bolts over a QR?

pro riders use vertical dropouts these days and the amount of force on the chain at 80rpms is enough less that at 0 that a strong ss rider with a small cog will in practice put high force loads on the wheel more frequently even if it is associated with less torque and power.

I second the shimano QR's. Been riding singlespeeds for over 10 years and never had anything slip. EVER.

I clamp it down tight and am currently running 45/16 & 42/19 and have climbed some steep inclines where I was *crawling* up the hill, such that it probably would have been just as fast to walk my bike up the hill.... and it still did not slip. Have mashed off the line and nada.... no slippy.

I have used salsa QR's on my singlespeeds and they do slip a little. The holding ability of a knurled aluminum QR just does not seem to work as well as a steel QR.

Another thing that helps are good lock nuts on the axle that have decent knurling. The shimano ones like in this pic:
http://img514.imageshack.us/img514/7995/hua19zt7.jpg
are OK but the knurling is shallow and the edges not sharp. I use old Campy locknuts that flare at the ends which has a larger diameter at the interface between the hub and the dropout.... it has more holding power. I also have had GREAT luck with old superbe pro locknuts that are REALLY grippy.

Cannot comment of FG, but for SS, there should be no reason you cannot use a QR

Per Sheldon Brown:

"As a result, it is widely believed that quick-release (http://www.sheldonbrown.com/gloss_q.html#quick) axles are not suitable for fixed-gear use. This is false! "

http://www.sheldonbrown.com/fixed-conversion.html

no matter what gear anyone here has on their bike they are never going to be able to generate the same amount of torque against that axle as a Pro rider can and they don't slip their QR so nobody here should be able to slip theirs.
Actually, that's not correct.

First of all, there's no "torque" against the axle other than the little that comes from bearing friction.

It's not the torque that's an issue, it's the linear pull on the chain.

The magnitude of this pull is directly proportional to how hard you push on the pedal, and the length of the crank. It is inversely proportional to the chainring size.

"Pro riders" don't need to push as hard on the pedals as clydesdales do, and in fact they can't do so, because their weight limits how much force they can apply to the pedals. (Lighter riders don't NEED to push as hard on the pedals, it's about power/weight ratio.) "Pro riders" can push hard for a longer period of time without getting all tuckered out, but the maximum chain pull they create is quite a bit less than an overweight tourist or mountain biker.

"Pro riders" rarely use a chainring smaller than 39 teeth, or occasionally 34 teeth if they run compact. Track riders rarely use a chainring smaller than the upper 40s.

Touring cyclists commonly have 24/26 tooth granny rings, which apply proportionally more pull to the chain for the same amount of push on the pedal.

For example, comparing a 24 tooth chainring with a 39 tooth, the 24 tooth ring will pull the chain 60% harder for the same amount of pedal force.

Sheldon "It's About Tension, Not Torque" Brown

I'm kind of confused by what you're saying Sheldon.

As I've understood it, since you're geared too high when starting from a standstill, the force of your pedalling is more than it should, so your chain is pulling harder. When you can spin on a geared bike instead of mash, you're trading an amount of force for an amount of chain pull. The chain isn't pulling as hard since it's moving faster.

Is this correct?

I'm kind of confused by what you're saying Sheldon.

As I've understood it, since you're geared too high when starting from a standstill, the force of your pedalling is more than it should, so your chain is pulling harder. When you can spin on a geared bike instead of mash, you're trading an amount of force for an amount of chain pull. The chain isn't pulling as hard since it's moving faster.

Is this correct?


In practice:
A smaller chainring will ALLOW the rider to put more force on the chain.
A smaller cog will REQUIRE the rider to put more force on the chain in order to put the same torque on the rear wheel.

Think of it in terms of leverage. You have your fulcrum at the BB axle, the load at the chainring and your force at the pedal axle. The closer the load is to the fulcrum (ie a small chainring), the easier it is to move for a given amount of force.

So with a big chainring, YOU need to push a lot harder on the pedal to get things rolling. Those with smaller chainrings may be putting less energy into pushing the bicycle along (from a standstill at least), but they are doing more work ;)

Think of it in terms of leverage. You have your fulcrum at the BB axle, the load at the chainring and your force at the pedal axle. The closer the load is to the fulcrum (ie a small chainring), the easier it is to move for a given amount of force.

So with a big chainring, YOU need to push a lot harder on the pedal to get things rolling. Those with smaller chainrings may be putting less energy into pushing the bicycle along (from a standstill at least), but they are doing more work ;)

This is exactly how you should not think about it.

You're only confusing me more radical_edward.

I'm just trying to think back to physics class. The total amount of energy is the same either way, but you either spin faster or mash harder. It's the mashing on a high gear ratio that pulls the wheel out. If you put your road bike in the same ratio as your SS/FG, you should experience the same thing with the wheel coming loose.

You're only confusing me more radical_edward.

I'm just trying to think back to physics class. The total amount of energy is the same either way, but you either spin faster or mash harder. It's the mashing on a high gear ratio that pulls the wheel out. If you put your road bike in the same ratio as your SS/FG, you should experience the same thing with the wheel coming loose.

it's not the gear ratio it's the size of the rear cog. If you use a large cog you move the mechanical advantage to a place where the wheel won't get pulled out.

it's not the gear ratio it's the size of the rear cog. If you use a large cog you move the mechanical advantage to a place where the wheel won't get pulled out.

OH!!!!

You're talking about the distance from the dropout on the plane of the axle!

Ok. Gotcha.

It's funny when people think higher gearing puts more force on the drivetrain just because it's harder to pedal. hahahahah

OH!!!!

You're talking about the distance from the dropout on the plane of the axle!

Ok. Gotcha.


No I wasn't. I'm not sure there is any lever there.

It's funny when people think higher gearing puts more force on the drivetrain just because it's harder to pedal. hahahahah

No but for the same amount of tourque applied to the wheel the one with the smaller cog will put more force on the drive train.

I'm kind of confused by what you're saying Sheldon.

As I've understood it, since you're geared too high when starting from a standstill, the force of your pedalling is more than it should, so your chain is pulling harder. When you can spin on a geared bike instead of mash, you're trading an amount of force for an amount of chain pull. The chain isn't pulling as hard since it's moving faster.
Might be correct if there weren't such a thing as hills. Track riders don't need to deal with hills, that's the main reason they don't have gears.

A heavy tourist on a loaded bike climbing a steep hill puts WAY more stress on the chain than any track rider ever does on the boards.

I think you may be confusing force and work. Work is force times distance. If you lug a 52 tooth chainring at 50 RPM, or spin a 26 tooth at 100 RPM the same amount of work is getting done every second. The rider with the 26 who is spinning twice as fast, is only pushing half as hard on the pedals. The chain can't tell the difference.

However, if the bike is going slow enough that the rider with the 26 is able to lean his/her full weight on the pedal, the pull on the chain will be twice as high.

Sheldon "Physics" Brown

I read somewhere that using a quick release was bad with single-speed bikes. This doesn't make sense to me, since the forces on the rear wheel should be the same regardless of whether or not you have a derailer.

I'm confused, it seems like no one addressed the issue? If so, please correct me.

But it's not apples-to-apples. Compare a derail to a tensioner, both apples.

The springs absorbing the force is the answer, yeah?

I read somewhere that using a quick release was bad with single-speed bikes. This doesn't make sense to me, since the forces on the rear wheel should be the same regardless of whether or not you have a derailer.
Correct. This is a widespread superstition. Good quality quick releases hold as well as nuts, if not better.

See: http://sheldonbrown.com/qr


But then the other day I totally mangled my derailer and had to do a quick conversion to single-speed to get home. The rear wheel slipped in the (horozontal) drop-outs two or three times, and I had to stop and realign it.Does your derailer mount with an adaptor claw like this?


http://sheldonbrown.com/images/adaptorclaw.gif

If you removed the adaptor claw with the mangled derailer, the axle stub on the right side may have been long enough to keep the skewer's acorn nut from gripping the dropout...it may have been pressing on the end of the axle. Sometimes removing the coniical spring from the skewer is a quick fix for this.

Sheldon "QR" Brown

RadioFlyer: As far as I'm concerned, the issue is solved.

Sheldon and everyone: I think we're looking at user error here. I have good quality Columbus forged dropouts, a good(?) Campagnolo skewer, and no adaptor claw. I have since put a new derailer on, but before I did I took it out for some serious (single-speed) mashing and it didn't budge a bit.

I don't know what was going on that day: I had the original destruction of the derailer (which I had attributed to bad derailer adjustment, but, in hindsight, may have been caused by a wheel slip) plus one or two slips while in single-speed mode. But given that it hasn't slipped since, I can only assume I wasn't clamping tightly enough.

Is it hard to set a good chain tension and straighten the wheel without being able to loosen one side at a time?

Is it hard to set a good chain tension and straighten the wheel without being able to loosen one side at a time?

Nope. You just tighten down the QR with one hand and pull the wheel back into the dropout/fork ends and grip down lightly on the QR lever. Once you have the desiered tension (and a centered wheel) you just grip harder on the QR to fully clamp the wheel.

Never had my rear wheel slip on my SS, EVER, when using a steel QR. Had one slip w/ a Salsa ti QR, but those don't have near the clamping force and the aluminum "teeth" don't really grip that well.

I grind up steep hills and never a whimper from the rear wheel..... I can hear my chain groaning, but no slippage.

simple


QR dropouts are fixed position, there is nothing to slide

horizontal dropouts (for adjusting chain slack) can slide, need bolts
or axle stops


no QR will eclipse a grade 8 bolt in tightness
if you tighten the bolt enough. unpossible. qr just cannot do what screw threads can do
for compression force

if you have horizontal dropouts and a qr and it doesn't slip, U are lucky but most peeps need
a surly tuggnut or something similar.

[QUOTE=Sheldon Brown;5297349]Correct. This is a widespread superstition. Good quality quick releases hold as well as nuts, if not better.
See: http://sheldonbrown.com/qr

Mr Brown.
I must preface that you have likely forgotten more about bikes, than I may ever know, but that statement is patently false in regards to my experience.

OFFROAD, I MUST use a tug on my Surly hub and steel track dropouts. The thing would dance with a QR hub on the track ends.

I notice subtle chain tesion variance after several hard backpedals even when using a tug and track nuts.

not trying to be disrepesctful, but my experience is contrary, not a superstition.

I've been losing the proper chain tension repeatedly on my bike (with quick release) during the first few pedals and back pedals immediately after re-setting the rear wheel. I've been periodically re-setting my rear wheel for about 2 months now. Although the slacking chain tension hasn't caused any problems, It just felt sloppy. Today, I'm glad I've finally discovered the problem: The hollow axle can move independently from the acorn nut and skewers; There's wiggle room for the hollow axle; Their centerline do not always align; If the acorn nut is in fixed in a position, it is still possible for the axle to slightly move fore or aft. I don't know if all quick releases are this way.



Previously, I would loosen the quick release and tug on the rim to increase chain tension. This is primarily pulling from the rim to the hub and axle, then the axle pulls the acorn nut and skewers. But this is also moving the axle aft in relation to the acorn nut and skewers. When I begin riding, the acorn nut and skewers doesn't slip on the dropouts (which I thought was the cause of the problem) and do remain where they are but it's the axle, along with the lock nuts, that move slighly forward and would cause the chain to lose tension. That wasn't a problem when the bike had the chain tensioner from the derailleur. I found that the proper way to increase chain tension is not by tugging on the rim but pulling on the acorn nut and skewer instead. This way moves the acon nut and skewers farther back than the axle so that the axle has no more wiggle room to move forward.



I noticed this this morning as I was trying to tighten the chain (again). I tried the newfound method when I got home and I just got back from doing some sprints and immediate slow downs by back pedaling and the chain tension is still how it was.



anyone else with quick release losing chain tension? might want to try this if my explanation even made sense.