Reach down to adjust brakes?

[nickw]

So I have been wondering this for quite some time. After a climb, when the riders are starting to descend they will reach down and 'adjust' their brakes front and rear. Why is that?

I know most brakes have the cam adjuster to open them up when changing a wheel, which spreads the pads further apart. Is that what they are messing with? Is it because of possible rub?

Any ideas?

[gmason]

Yes. But only on Shimano (and now SRAM, I think). Campagnolo's adjustment is on the hoods.

[jahona]

I think I remember reading that during climbs the wheels will flex and rub on the pads, so they open them on the uphill and engage them again on the downhill. I guess that flex happens when you have superlight climbing wheels.

[meb]

I think I remember reading that during climbs the wheels will flex and rub on the pads, so they open them on the uphill and engage them again on the downhill. I guess that flex happens when you have superlight climbing wheels.

That would make sense that the lower or more heavily loaded wheel might flex into the pads- which would mean the rear whilst climbing and the front whilst descending. Can anyone confim them flexing more as a function of load?

[chevy42083]

You mean weight load, or stress load?

Stress yes, but upon decent, I'm sure both front and rear calipers are "closed". It's the sideways stressing of cranking up the hill causing the flex, not the vertical weight load of the bike and rider.

[jschen]

I have never noticed that, but it begs a question from me. So how much does flex really affect performance? Evidently not much (if at all) if the pros are willing to make this tradeoff for a slight weight reduction. Even if more flexy wheels robbed them of 1% of power, they'd be way better off running somewhat heavier, less flexy wheels, right?

[gmason]

I have never noticed that, but it begs a question from me. So how much does flex really affect performance? ...

When climbing, a lot if the wheel keeps rubbing the pads. It's hard enough without the extra friction.

[FIVE ONE SIX]

i can see them opening the rear pads on a climb and closing them on the descent, but i don't see why they would need to do that with the front wheels, the front wheels aren't flexing...

[meb]

You mean weight load, or stress load?

Stress yes, but upon decent, I'm sure both front and rear calipers are "closed". It's the sideways stressing of cranking up the hill causing the flex, not the vertical weight load of the bike and rider.

I was thinking weight, but I see why light wheels would flex from the cranking.

[kesa101]

it's also psychological! i do it all the time about half way up a climb, convincing myself (well, not really, but hey, whatever works) that i'll go faster... remember though - readjust for the descent!

[Jesus Christ]

Yes. But only on Shimano (and now SRAM, I think). Campagnolo's adjustment is on the hoods.












wrong. check the calipers.

[gmason]

wrong. check the calipers.

Explain please. On what year and gruppo do Campas adjust at the caliper? I have not seen one.

We are not talking about the cable adjustment here - the round cam mechanism at the caliper - just the quick release aspect as the OP described.

[gmason]

re the cam adjuster: I see that in 2008 at least, above the Centaur level the round adjuster has become a little cross-shaped piece. That could make it a little easier to do adjustments - the rubber band on the originals could get quite slippery at times.

[EDIT] Actually, the new shape appears to have arrived with the skeleton brakes.