Break pad rubs tire. Why?!?!

[trekingmadrid]

Hey all, a break pad problem that I am at my wits end on fixing.

I ride a Trek 1000 and, upon deciding to try to fix the weak spongy brakes that it has had for a long time (I've just started riding again after a few years off), I noticed that the top edge of the front left brake pad rubs slightly on the tire and has worn the pad funny -- no noticeable wear or damage on the tire, but it can't be good for it of course.

It has the stock Shimano side-pull breaks, and I have tried every adjustment I can find, but don't find a way to fix it. The right pad is perfect, falls perfectly in the center of the rim wall, is toed in nicely, and gives no problems, but the left pad makes contact high on the rim with the top edge hanging over towards the tire. The brake shoe is all the way at the bottom of the slot in the caliper arm. The caliper appears centered, and I don't see any other obvious problem or possible adjustment.

The one other oddity that I notice is that, when squeezing the breaks, the right (good) pad goes slightly downward from horizontal as it moves towards the rim. Whereas the left (bad) break pad moves upward a bit, ending up too high on the rim. From what I can see about the way the caliper mechanism works, this looks inherent in the construction of it, but maybe I'm missing something that can be adjusted?

Any help would be GREATLY appreciated.

Thanks!!

Tyler

 

[TKOS]

The pad has shifted. Sometimes a good bump can do that as they are held in place by a single bolt. Get an allen key and unscrew the bolt. Reset it so that it doesn't rub. If that doesn't make sense then I suggest going to the Park Tools website and checking out brake adjustments. It is a great site to see.

If you adjusted the tension it can sometimes throw off wear the pad sits, so the pad itself needs adjustment.

 

[trekingmadrid]

TKOS, I wish it were that simple. But I have made all the basic adjustments I know of on the brakes short of removing the caliper (adjusted pads, cables, centered caliper, centered wheel, etc), but I can't find any way to make it sit down lower on the rim. I've got the break shoe bolt as far down in the adjustment slot as it will go. In fact, after writing the original question I went on to adjust the cables and pads on the back and, while neither one hangs over the edge, both back pads are also adjusted as absolutely low as possible and still sit close to the outer edge of the wheel.
It looks to me as if the caliper arms are somehow not really made long enough to get the pad where it goes, but I can't imagine that the bike came with stock parts that don't fit right.

So short of filing out a bigger slot to allow it to sit further down in the caliper arm, I don't know what else to try. Either a technical adjustment I don't know how to do (which wouldn't be surprising, I'm quite novice) or some other problem I'm not seeing. Been trying to avoid shops and get to know my own bike and fix it myself, but it looks like I might be out of options on this one.

Anybody else have any other suggestions before taking it in?

 

[skinnyman]

Hey trekingmadrid, I'm in the same position as you ... same bike, too. My pads (left only?) run high, in fact I've gotten a couple of flat due to the pad rubbing into the sidewall. I stopped at a bike shop yesterday to see if they'd seen it before - nope.

Have you found any solution besides filing down the slot for the brake shoe? I'm about to do this unless I find some other info to the contrary.

 

[davereo]

Your entire caliper is off center. The reason you can not lower one pad enough is because the caliper needs to be adjusted back on center. Screw the barrel adjuster all the way in. Loosen the caliper and center it over the rim. Tigthen the caliper and reposition both pads to line up with the rims braking surface. Both pads will need to be adjusted to get your brakes lined up right. Screw the barrel adjuster backout.

 

[skinnyman]

Thanks for that, davero!

You got me to take another look at the caliper centering. It was the small adjustment screw that needed to be turned in significantly from where it was. I haven't ridden the bike yet, but it looks to be much better. /img/vbsmilies/smilies/icon14.gif