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"Please tell us how - I didn't know there was any adjustment to be made."
have you checked that your looking at the brakes and not a VCR, a betamax or something like that ? there are alot of adjustments immediately obvious.
the key thing is to use the mechanical leverage.... ie dont set the pads a mm away from the rim , you need the lever to travel a good distance and youll find your power improves and becomes much less wooden - common mistake most amateur MTB mechanics make winding them right up so the brake contacts the rim in the first few degrees of pulling the brake lever.
I really don't understand the opposition to choice.
I really don't understand the opposition to choice.
Choice = incompatibility.
there are alot of adjustments immediately obvious.
On road brakes? Distance from rim is one - what else?
ransos - MemberChoice = incompatibility.
😐
Its not a fact Monkfinger.
Erm, yes, it is, cynical.
It's the same fact which means every car manufactured today has conical nuts holding the wheels on - so reversal of forces (obviously on a car that happens with every wheel revolution) do not loosen the nuts.
More generally, it's the same reason why any threaded fastening can vibrate undone.
Denying it doesn't make it not true.
On road brakes? Distance from rim is one - what else?
Pad position (maybe alignment too). Pad material/compound.
and
Cleanliness of cable & outer go toward removing friction. Nicely cut (i.e. square ends not a half-assed effort) outers mean you don't have to "squash" the end of the cable as you brake.
Both of which go toward less braking effort at the hand for same braking effect.
Well I have had qrs with discs on non lipped forks that have not loosened.
Saying its true does not make it true either!
height of the pad on the rim , angle of the pad - fore and aft as well as vertically , centralisation of the caliper , ensuring the caliper is free to move , ensuring the lever is in the correct place for your hand to operate it propperly - plus what mrmonkfinger saids
Its not a fact Monkfinger.
Indeed, but it is the case that the forces that can be created by a disc brake are uncomfortably close to the clamping force required by the ISO standard for QRs, so you're relying on the QRs exceeding the standard, and on people operating them correctly.
Well, turns out that people are fallible, and given the potential consequences of wheel ejection, it seems sensible to use a mechanism that is less reliant on the user getting the tension on a QR just right.
The higher braking forces possible from rubber-on-tarmac, coupled with the smaller discs that seem to be fashionable on road bikes means the force on the axle is potentially higher than on an MTB.
As for the whatnobeer's generalisations, I have disc brakes on my commuting road bike because a) they wear down a sacrificial metal disc rather than a structural part of my wheels and b) they behave predictably in the wet. I'm in no great rush to have them on my summer road bike as the rate of rim wear is pretty much negligible, but I'd be happy enough to have them in the future.
"It doesn't alter the fact that, with current 'slot dropout QR + disc', braking will cause gradual loosening of the QR."
of shit QRs .....
I generally ride from the door or throw my bike fully built in the van , the only time i take tires off is when i get a flat - so its not like they get checked every ride - or even every 10 rides.....
when ive had skewers that come loose gradually(usually cheap ones or Hope) - i bin them and fit propper skewers from a good manufacturer. - such as shimano with propper internal cam QRs.
"It doesn't alter the fact that, with current 'slot dropout QR + disc', braking will cause gradual loosening of the QR."of shit QRs .....
My Specalized Tricross unwinds the front QR under heavy breaking regardless of the make. I even used the tried and tested Shimano QRs, yet they still undo. I've never worked the problem out, but I think it must be a fork design issue, on top of the forces acting from the disc.
It doesn't alter the fact that, with current 'slot dropout QR + disc', braking will cause gradual loosening of the QR.
If you'd said
It doesn't alter the fact that, with current 'slot dropout QR + disc', braking will cause forces that [b]can result in[/b] gradual loosening of the QR [b]if insufficiently tight[/b].
Then you'd be correct. Just because the force is there doesn't mean it's an issue in itself.
Well I have had qrs with discs on non lipped forks that have not loosened
I've got QR forks with discs. The QRs have never loosened. So what?
Sample size of 1 (again).
shit QRs
...
fit propper skewers from a good manufacturer. - such as shimano with propper internal cam QRs.
this is kind of the point - a decent QR will (a) clamp harder in the first place and (b) stay tight much much longer, maybe even so long that you'd never notice the problem... wheras a tossy lightweight (coughroadiecough) skewer with plastic cam has all the clamping force of a wet flannel and will come loose much muh easier with a painful result
also, smaller brake disc = more force applied to axle & hence more likely to loosen the QR
I've got QR forks with discs. The QRs have never loosened. So what?
It disproves your assertion. If you'd said "may" instead of "will" you'd be correct.
An analogy is pushing against a wall. If it's flimsy then I might push it over. If it's not or I don't push hard enough it will never fall over no matter how long I push. The decent QR done up properly will never move. You seem to think it will just move very very slowly. It won't.
Surprised nobody's mentioned them already, but my Giant wheels came with [url= http://roadcyclinguk.com/gear/dt-swiss-rws-qr-skewers-tested.html ]DT RWS skewers[/url] that you screw rather than lever. On the back, i'll be honest, they are a pain. On the front, they are fantastic, just unwind until you can drop the wheel out over the lawyer lips - much faster than normal QRs.
And of course you can instantly see whether they are unwinding. I've not tried them on disk wheels, but after my new Hopes loosened on the last ride, I'll give them a try. They really are very good (on the front).
The decent QR done up properly will never move. You seem to think it will just move very very slowly. It won't.
If the vertical(ish) force from braking is greater than the opposite vertical force from rider weight, then you get mechanical precession. The tightness of QR doesn't come into it, braking force does.
The tightness of QR [i]does[/i] affect how quickly that precession will result in the QR coming loose. An extremely tight QR would mean very little effect from the precession, but not 'no effect'.
It disproves your assertion. If you'd said "may" instead of "will" you'd be correct.
you're right, I should have said "never noticably loosened".
Except that (good) QRs actually bite into the dropouts (see the marks left) which stops that actually happening. One reason why Hope's original QR design with concentric ridges on the dropout facing surface was so crap.
Fair point - although dragon's experience would imply that they're not enough to prevent it happening.
I'm going to suggest that the dropout on those forks are particularly hard maybe so that the QRs don't bite in - steel fork maybe?
So Monk, you seem reluctant to fully concede your point.
Seems plenty of folk have ridden qr forks with discs without loosening (even only noticably 🙄 ).
Is this a sort of "infinite monkey" point?
They are aluminium. Maybe over the weekend I'll have a look at how marked they are.
If the vertical(ish) force from braking is greater than the opposite vertical force from rider weight, then you get mechanical precession.
Mechanical precession occurs where you have a rotating radial force, not just an alternating one, and the resulting force is dependent on the direction of that rotation. This is why it only affects pedals or bottom brackets on one side of a bike, and why switching to left handed threads fixes it.
If the issue of QRs undoing was down to precession, then surely switching to left handed threads would fix the problem?