Quick release rear wheel

[oncemore]

By 'eck I neer knew it wer' al' so complicated...

[border-rider]

So, another question for the mathers:

can you (ie an average rider) put more pressure on the QR holding the wheel in by climbing up a real steep hill, or by trying to do an emeragncy stop by leg braking?

I ask, because being weary of the back wheel dislodging, I don't tend to leg brake much but if leg braking is much less likely to move the wheel than climbing then I might start again.

Without engaging my physics brain I think the answer is that you can put more force in when just stalling going forwards on a steep hill than when you backpedal.

[JJ]

Without engaging my physics brain I think the answer is that you can put more force in when just stalling going forwards on a steep hill than when you backpedal.

Hesitating to expose my ignorance in public.....but doing so nevertheless.  From my recollection of riding fixed "some time" ago, it was quite easy to lock the back wheel in a moment of panic-induced kick-back.  I don't remember ever spinning it while climbing.  The implication is that kick-back can indeed produce more tension than drive, perhaps only in a moment of panic.

But then it was a long time ago.

[Greenbank]

I think MV is correct.

To wheelspin you need to break the friction between road and tyre with no resistive force on the rims.

With leg braking, or general braking (think how little effort you have to put in on a brake lever to cause the rear wheel to lock), you're using the momentum of the bike and rider to break the friction between road and tyre once you've locked the wheel from turning.

[border-rider]

I think also that momentum tends to unweight the back wheel a bit.  But I must admit I can't skid-stop anyway, unless I'm running a very low gear or going down a very steep and slippy hill.  I reckon I can climb hills that I can't leg-brke to a standstill on.

[Crumbling Nick]

My fixed is a Claud Butler Audax 531 frame with forward-facing dropouts - and a nutted wheel tightened with two spanners, a great deal of force and a final tighten with a foot on each spanner ... but I'd really like some insurance too in the form of a chain tug of some sort

Rob

I wouldn't bother. Chain tugs are a bit of extra hassle if you have a derailleur hanger.

My frame is of the same material and I only use a standard Allen key (about 80 mm long) and hand pressure to tighten the Goldtec bolt, which doesn't even have a serrated washer. I don't get slip. At a guess, you have 4 times a much resistance to slip as I do, unless you have chromed drop-outs or some other slippery finsh.

[Crumbling Nick]

I think also that momentum tends to unweight the back wheel a bit.  But I must admit I can't skid-stop anyway, unless I'm running a very low gear or going down a very steep and slippy hill.  I reckon I can climb hills that I can't leg-brke to a standstill on.

That's my experience as well.

[Crumbling Nick]

I thought a QR can actually be tighter than nuts.

That sounds plausible, given the scepticism that must have accompanied their introduction (in 1920 according to Sheldon), though it appears that wing nuts were the norm in those days.

Thought for the debate... If those guys coped with only the leverage of wing nuts, why are we worrying so much?

[oncemore]

"...tightened with two spanners, a great deal of force and a final tighten with a foot on each spanner ... "

So do you carry two spanners with you all the time? Sounds a bit unnecessary to me - and I doubt you need the "insurance ......of a chain tug"!

"If those guys coped with only the leverage of wing nuts, why are we worrying so much?"

Ah but they wuz real men in they days. And I'm not (worrying so much, that is!).

[donpedro]

I thought a QR can actually be tighter than nuts.

That sounds plausible, given the scepticism that must have accompanied their introduction (in 1920 according to Sheldon), though it appears that wing nuts were the norm in those days.

Thought for the debate... If those guys coped with only the leverage of wing nuts, why are we worrying so much?

A good nut has three times the force of any QR, period!
With a solid axle it's also many times stronger and more durable.
Question is if you need all that force and willing to find out the hard way?

I wasn't and think the one I used was a simple Shimano solid CroMo-steel axle for three-speeds or such. A hours job and cost with nuts came to £10.

[Crumbling Nick]

A good nut has three times the force of any QR, period!
With a solid axle it's also many times stronger and more durable.

Can you provide a source for those two assertions?

[rogerzilla]

You can probably work it out...but I can't be bothered, and I don't know the cam size of an average QR.

[donpedro]

A good nut has three times the force of any QR, period!
With a solid axle it's also many times stronger and more durable.

Can you provide a source for those two assertions?

Yup, just read it in a very refreshing article by Grant Petersen while taking a dump:
Rivendell Reader Issue 2 Vol 1 (June/July issue 1995) page 7,
"Interview with Roger Durham". He's the owner and designer of Bullseye Cycle:
Bullseye Cycle USA 35 Years of Cycling

[border-rider]

You can probably work it out...but I can't be bothered, and I don't know the cam size of an average QR.

That was exactly my reaction.

The q/r lever is about 3/4 the length of the Jethro Tool I use on the track nuts on the MC,  so the cam'd need to give you a leverage of 4 or so...

Whether solid/hollow axles are stronger depends on what they're made of too.  I must admit that the only axles I've ever bent have been solid, but they've been cheapo ones.  CrMo solid or hollow is plenty strong enough either way

[rogerzilla]

You'd have to make some sort of assumption about friction too, and I guess it's lower in a small polished QR cam than it is in a less polished nut's worth of threads.

[border-rider]

True.

But friction's a dynamic force so in the limit, as you tighten it down, won't it be not-very-relevant ? 

[rogerzilla]

I don't think so.  It's easy to observe that a spot of lubrication can allow the QR adjusting nut to be screwed in a bit more while still permitting the lever to be closed, allowing much more effective clamping.  Likewise, with dry and dirty threads you can reach the limit of hand strength on the spanner before the wheel is held properly.

[Crumbling Nick]

A good nut has three times the force of any QR, period!
With a solid axle it's also many times stronger and more durable.

Can you provide a source for those two assertions?

Yup, just read it in a very refreshing article by Grant Petersen while taking a dump:
Rivendell Reader Issue 2 Vol 1 (June/July issue 1995) page 7,
"Interview with Roger Durham". He's the owner and designer of Bullseye Cycle:
Bullseye Cycle USA 35 Years of Cycling

Is that article available online? I'd like to read it.

[Crumbling Nick]

You can probably work it out...but I can't be bothered, and I don't know the cam size of an average QR.

I think the first one has too many unknowns.
The second one may be OK for values of many that are less than 2.

But I'm not an engineer .

[rogerzilla]

I am (or at least, I have a degree in engineering), and I still can't be bothered 

[donpedro]

A good nut has three times the force of any QR, period!
With a solid axle it's also many times stronger and more durable.

Can you provide a source for those two assertions?

Yup, just read it in a very refreshing article by Grant Petersen while taking a dump:
Rivendell Reader Issue 2 Vol 1 (June/July issue 1995) page 7,
"Interview with Roger Durham". He's the owner and designer of Bullseye Cycle:
Bullseye Cycle USA 35 Years of Cycling

Is that article available online? I'd like to read it.

I have no idea!

[nuttycyclist]

So, another question for the mathers:

can you (ie an average rider) put more pressure on the QR holding the wheel in by climbing up a real steep hill, or by trying to do an emeragncy stop by leg braking?

I ask, because being weary of the back wheel dislodging, I don't tend to leg brake much but if leg braking is much less likely to move the wheel than climbing then I might start again.

I left the maths in the classroom as it doesn't work outside of school.   In real world circumstances I found that leg breaking was what pulled the wheel forward on frankenfixie.   

The few times I forgot and slammed it into a skid stop from high speed I then had to get off and put the wheel back in.