denada

anyone have a link on how to adjust trek 700 brakes? it's a '92, in case the brakes changed over time. i can't even figure out what the brakes are called. i figure v-brakes, but all the videos and step-by-step guides for v-brakes look significantly different from my brakes.

after changing a flat tube and putting the rear wheel back on, the rear brake is ****ed. do not understand what happened.


thanks!

edit:
oh, maybe because they're cantilever brakes. figuring that out didn't help at all. these brakes have no centering screw, or it looks different than in the videos

katsup

Post a photo of the front as well as both sides of the brakes.

DorkDisk

They might have wrench flats for spring tension. I was trying to point you to Keith Bontrager's guide to cantilever setup but it seems like the internet black hole ate it up, along with his rants against oversize everything, what quality means, and other gems.

This guide seems a good place to start

Edit: This is the MBA article I read BITD on how to adjust canits. Every month they would have a how-to section. Cantis came up quite a bit

denada

there an allen wrench screw on one side. twisting it didn't help me. it's now all the way tight.

when the wheel spins, the left side rubs. it also gets stuck on the rim when the brake is pulled, demonstrated in the video.

hokiefyd 

It looks like there's a lot of corrosion on the brakes and on the bike in general. It's only a guess, but I'd say the internal return spring (one or both of them) may be broken, or the adjuster may be seized or stripped. It doesn't look like the brake pad or shoe is getting stuck on the rim or tire (through physical contact) -- it may be an internal problem with that brake arm on its mount.

I think your only option, if you want to save these brakes, is to remove them from the bike and try to lubricate what you can and see from the backside of the arms if anything is broken. Alternatively, new brakes aren't very expensive, and it may be worth it to simply replace them. Shimano's CT91 cantilevers are pretty inexpensive (about $10 per wheel, new), and are a good option for recreational riding. There are, of course, other styles as well. I have Tektro CR510s on one of my bikes, and I like these a lot because they use threaded post brake pads (very easy to setup).

denada

it’s definitely getting stuck on the rim through physical contact. i accidentally took the breaks apart. the springs are in place and working. the bike is just dirty because it’s winter.

everything was fine until i removed the wheel to change a flat. i think maybe the back wheel was not all the way seated in the frame when a shop adjusted the breaks. that guess is very much a guess, as i obviously don’t have the expertise to know.

dabac

Generally, there is a flange at the base of the brake boss. This flange usually has three holes in it. The return spring - one way or another - anchors into one of those holes. If you bottom out the fine adjustment screw, pull the brake arm off, reposition the return spring anchor point and reset the fine adjustment screw.
Keep in mind that you can move the spring on both sides.
I think we’re up against a language issue here. ”Stuck on rim” usually refers to when a brake pad overhangs the brake track towards the hub side, and gets hung up there.
You don’t seem to have that. Yours is simply getting stuck against the rim. Not retracting freely.
Most cantis and v-brakes don’t pivot directly against the post, but around a bushing pressed into the brake arm. Bad-weather use can cause dirt to get in between bushing and arm, preventing the arm from moving freely.
Some canti/v-brakes do pivot directly against the post. These too can suffer from contamination, but also be bolted in too hard to move freely.
Either way, make sure the brake arms do move freely. Remove the wheel if you have to. If they aren’t moving freely, lube, jiggle arm, repeat. Continue until arms do move freely. Reinstall and try again.

denada

the pad is worn at an angle. when it becomes pressed against the rim, it sticks the because the angle of the pad locks it in place against the rim. if the wheel is not there, the break moves fine. when the wheel is there, the pad makes contact at an angle that causes it to stick there. it gets stuck against the rim because the rim is there.

also the breaks are sitting at a funky angle. like tilted to the left.

i see the three holes you are talking about. i figure moving them would increase the spring tension. but that little spring could never have enough tension to free the break from the rim once it's wedged in place. i have to pull reasonably hard, so that the bottom edge of the break pad slips free.

i would think the breaks need to move to the left and be straightened out. i know the left one needs to move to the left, somehow. because even when it is not stuck against the rim, it's close enough to rub. nothing i do makes these brakes move to the left. i've screwed and unscrewed everything i can find to screw. only thing i cannot do is move the pad independent of the arm. the bolt is too stuck to remove with the tools i have.

denada

i'm taking it to the shop. i'll report back with what was actually wrong. i'd like to learn how to do this stuff. it's not that these repairs are too expensive; it's inconvenient. i'd like to be able to make minor fixes to my bike so i can use it.

denada

guy wasn't who worked on it wasn't there when i picked it up, so remains a mystery.

also, i went down like a brick on the ice today.

but that's fine. my commuter works again. free like a bird.

appreciate everyone's attempts at guidance. one day i'll be able to fix my own bike.

DorkDisk

These look like GS brakes to me. They were rubber coated steel and not worth fixing up too much.

Did you remove the brakes, take it apart, clean all the parts, and put it all back together? That'd be my first step. If it still doesn't work, I'd get some aluminum brake calipers with quality hangers and nice pads. There is only so much dirty low end hardware can do.