Why is the front QR release always on the left?

[andrew_s]

if there were a strong tendency for the nut to precess and then unscrew with the QR installed one way then presumably the whole QR could unscrew from the nut with comparable ease when it is installed the other way round....?

It wasn't so much precession I was thinking of, but more this sort of thing:
http://www.boltscience.com/pages/vibloose.htm

If the threads are the other end of the skewer from the (possible) up and down movement, there's at least some chance that skewer flex will take the sting out of things

[Brucey]

under particular vibration conditions some bolts (in industrial settings) can lose all their preload. They are then (momentarily) completely loose. Smaller vibrations can cause partial loss of preload. I don't think these conditions are at all likely to occur in a bicycle QR. What does happen with conventional QRs is that the axle can start moving around because the clamping force offered by the QR isn't enough to withstand the braking forces when using disc brakes.

If this comprises simple back and forth sliding then it shouldn't directly promote a net unscrewing of anything. However if it comprises an orbital motion it will.

I note that the fatigue resistance of the threaded end will be less than the plain end; however the clearance between the threaded part and the bore of the axle is also increased, which means that the loading on the threaded part (if that is set to the left) is likely to be considerably less if the movement is smaller than the clearance on offer. Thus the lever end of the QR might start sliding around on the face of the dropout under conditions where the nut would stay put.

So I guess that the best way round might vary depending on what you expect to happen, exactly.

cheers

[Cugel]

It's always on the left if you always put it there. No other reason. I always put it on the left but having read Brucey's sensible suggestion I'll switch to always putting it on the right on my dynamo equipped bikes.

Just so - many of the reasons offered up in just this thread are rationalisations after the fact for following a convention. On the other hand, some reasons do have a cogent logic-driver, such as the Brucey dynamo explanation. Others are logic based on imaginary premises.

We humans do love to justify ourselves. Perhaps this is because we're told that we're responsible for everything we do? In practice, it's some long forgotten historical twitch that decides if we do this or that.

If that's the case (historical twitch puppeting) perhaps we should all be more sceptical of our everyday habits? I try to be, myself; but being an old dog - albeit one who likes new tricks - I like the old tricks a lot, as well as the comfort of my various well-used baskets. However, I may go to the bike shed now and swap the QRs around, on principle. Also I will point them in an unusual direction, such as forward. Why not?

Cugel, getting ready for "reasons why QR levers should be aligned this way rather than that".

[Brucey]

.... However, I may go to the bike shed now and swap the QRs around, on principle. Also I will point them in an unusual direction, such as forward. Why not?....

the fashion police will be after you...!

But BITD race scrutineers used to be fussed about how your QRs were pointed (on safety grounds) and curved QR levers arguably only exist at all because of CPSC rules in the USA. If you have your QR levers pointed at a funny angle and you run into someone injuring them in an unnecessary fashion, you would feel a bit gutted.

As might they....

cheers

[mig]

forward facing QRs are not very 'aero' ...er...dude.

[Cugel]

.... However, I may go to the bike shed now and swap the QRs around, on principle. Also I will point them in an unusual direction, such as forward. Why not?....

the fashion police will be after you...!

But BITD race scrutineers used to be fussed about how your QRs were pointed (on safety grounds) and curved QR levers arguably only exist at all because of CPSC rules in the USA. If you have your QR levers pointed at a funny angle and you run into someone injuring them in an unnecessary fashion, you would feel a bit gutted.

As might they....

cheers

I do recall the rooles imposed by the race marshals concerning the QRs (and much else). Being very co-operative (and also wanting to take part) I was very conformant.

But in ordinary non-racey cycling, I avoid QR-gutting by never riding into anybody. I feel this is only good manners. Of course, if I did, the front tyre would get them first. I suppose a glancing blow might allow a pokey QR lever to pierce their kneecap but what if the glancing blow was on the drive side and I was in the smaller chainring!? Multiple knee-stabbing with a goodly portion of the 52 chainring biters!

No, I think I'll just go on avoiding these collisions with other humans. Even one with a stabbed knee might turn nasty.

Cugel

[Cugel]

forward facing QRs are not very 'aero' ...er...dude.

I have calculated the extra drag and it amounts to 0.00479 watts at 78kph (my usual speed). This seems too much of a loss so I will take your advice and re-arrange them skewers. Perhaps I should just remove them and keep the wheel in the dropouts with a drop of loctite? They're sure to make some for the purpose.

Cugel

[mig]

at that speed the plume of disturbed air will cool your disc brakes dude.

good trade off against the loss of watts.

#alwaysthinking

(with the 'h')

[rmurphy195]

its convention, partly a practical one too, of keeping you away from the chain etc when working on the bike.

FWIW I usually put the QR on the RHS of hub generator wheels; I reckon it increases my chances of remembering to disconnect and reconnect the wiring, as well as leaving all the work on one side of the wheel.

With disc brakes it is probably a good idea to have the lever on the RHS too; there have been some nasty accidents with the QR lever going into the disc itself accidentally, but more prosaically you are not so likely to burn your hands on the disc is the lever is on the other side.

cheers

Exactly why I'm asking - often when undoing the QR Iend up (nearly) "leaning" on the disc instead of the fork leg!

[Brucey]

its convention, partly a practical one too, of keeping you away from the chain etc when working on the bike.

FWIW I usually put the QR on the RHS of hub generator wheels; I reckon it increases my chances of remembering to disconnect and reconnect the wiring, as well as leaving all the work on one side of the wheel.

With disc brakes it is probably a good idea to have the lever on the RHS too; there have been some nasty accidents with the QR lever going into the disc itself accidentally, but more prosaically you are not so likely to burn your hands on the disc is the lever is on the other side.

cheers

Exactly why I'm asking - often when undoing the QR Iend up (nearly) "leaning" on the disc instead of the fork leg!

IIRC the biggest cycle recall in history was implemented when it transpired that several big brands shipped thousands of bikes with disc brakes and (Taiwanese?) hubs with QR levers which could potentially flap into the brake disc. Putting the lever on the right avoids this. Needless to say some people had to die/be seriously injured before the recall was implemented. I have every reason to suppose that there are plenty of bikes still out there which are similarly affected.

cheers

[mattsccm]

Seriously injured touching a got disc?
A) they don't get red hot although I have had them change colour
B) its a glancing touch not having it shoved in an orifice.
C) it's a tiny burn not multiple limb amputation.
Touching a hot disc is natures way of telling you that you are a bit thick.
A qr tucked under a caliper is out of the way.

[Brucey]

[Wanlock Dod]

my understanding is that because horses were always mounted from the left (regardless of country) so were bicycles, and it made sense to keep out of the way of the chain. Hence chain goes on the right.

cheers

My understanding is that one generally mounts a horse from the left because that is the only practical side to mount from if you are right handed and have a sword dangling from your left hand side. I assume that left handed folks would mount a horse from the right. I have never seen anybody ride a bike with a sword but I expect that the same mounting issues would apply.

[Brucey]

I'm not sure I'd ask her....

[foxyrider]

Given that the majority of people are right handed it makes sense, stand in front of the bike and do the lever up with the right hand - knowing this is a boon to race mechanics (for whom the system was effectively fine tuned for), you don't waste valuable seconds trying to work out where the lever will be.
The rear is more complex, you need two hands to extract the wheel and in this case the more dextrous hand has to cope with the gear mech leaving the often weaker left hand to undo the QR, apart from safety concerns, that's one reason they should face backwards to give you easier purchase to undo them.