[Mudpuppy]

I have hayes mechanical disc brakes. The rear is a six inch rotor. Over the last maybe 3 rides the rear brake has pretty much stopped workin. I can coast down gentle hills with the brake full on.

Does anyone have any suggestions on how to fix this, or what the problem might be?

Thanks for the help.

 

[Orvan]

Originally posted by Mudpuppy
I have hayes mechanical disc brakes. The rear is a six inch rotor. Over the last maybe 3 rides the rear brake has pretty much stopped workin. I can coast down gentle hills with the brake full on.

Does anyone have any suggestions on how to fix this, or what the problem might be?

Thanks for the help.

maybe adjust the cable tension......

 

[Orvan]

oh and you have the best avatar by a long stretch

 

[sub6]

Perhaps your pads are worn off.

Or perhaps you got some chain lube on the rotor and it's too slick to stop.

In either case, clean the rotor with alcohol (b/c you should do that anyway from time to time) and get a new pair of pads.

I can't think of anything else...

 

[Mudpuppy]

Ok thanks for the suggestions and thanks for the avatar compliment.

I tried adjusting cable tension and it just makes it grab sooner, but I keep rolling just as easily.

could I use fingernail polish remover on the rotor? I just moved into the dorm and I don't have any alcohol though i do have non-acetone fingernail polish remover.

 

[Roasted]

You could take the hayes hmx apart (I just finished doing this myself) and overhaul it but regreasing the bearing. There are bearings you can ensure are still bearings. This is actually a fun job, you learn a lot about the mechanics of the brake.

Take the wheel off of the bike. Squeeze the brakes. Do they touch? Are they close? If they have a gap you need new pads. I am having the same problem with my front brake (a far mroe dangerous situation) and I tried everything. While most things helps I am now sure it is worn pads.

To be honest I just find these brakes suck. My v-brakes were more consistant and offered close power. These things either work AWESOME or not at all and need adjustment.

 

[Rustmouse]

sounds an awful lot like yer pads are worn off...

 

[Mudpuppy]

Ok this evening after classes I'll take the wheel off and check things out.
I'll keep you updated on what's happening

 

[sub6]

This may be a dumb question, but you DID tighten the pad adjuster to account for the pad wear, didn't you? On a mechanical disc, as the pads wear down, you have to tighten the pad adjuster to bring them closer to the rotor.

This isn't necessary, of course, on most hydro discs, which are self-adjusting.

Also, I don't know if nail polish remover will work, but you're in a dorm? And you don't have alcohol?? Get with the program, man!! j/k - it's only like $1.00 for a bottle at the drug store; pick some up it's great stuff (unless you drink it, then you die ).

 

[sub6]

the point of my above post is that you may not need to replace the pads, just turn the pad adjuster.

 

[Mudpuppy]

Any pictures of exactly what the pad adjuster is? I've looked at the brake before and the only adjuster I found turned about 1/4 turn and did about 0 good. A good explination of what it is would be good.

 

[Mudpuppy]

There probably is alcohol here, but I'm not into that stuff so I wouldn't know where or who to get it from. I'm also in the honors dorm so things are a bit quieter here.

 

[sub6]

Originally posted by Mudpuppy
There probably is alcohol here, but I'm not into that stuff so I wouldn't know where or who to get it from. I'm also in the honors dorm so things are a bit quieter here.

oh, I mean rubbing alcohol - totally legit stuff - get it at any drugstore or walmart.

Pad adjuster-wise, I dont' know about Hayes HMX b/c they aren't as common as the similar Avid brake, but on the Avid there's a great big red knob on the side of the brake, and you turn it clockwise to move the pad closer to the rotor. The other (fixed) pad is adjusted by a set screw on the backside (wheel side) of the caliper, but it's not necessary to adjust it as often.

Most mech. discs work this way, there should be a pretty easy way to account for pad wear.

 

[sub6]

Okay, this is starting to not look good. I'm looking at the HMX manual on the Hayes site Here.

It looks like there is no adjustment for the moving pad (there's one moving pad and one fixed pad) which is pretty crappy. It looks to me like you need to do this:

1 - loosen the bolts that hold the brake to the frame - the bolts go through a pair of slotted holes. With the bolts loose, you should be able to move the brake sideways so that it bumps the rotor on each side.

2 - squeeze the brake lever hard and hold it there. the pads should squeeze the rotor and this will tend to center the caliper over the rotor; you may have to poke at it a bit to get it to move where it needs to be (centered).

3 - while still holding the lever down, tighten the caliper bolts. This will lock the caliper in position.

4 - at this point, if you let go of the lever, the wheel will spin but the fixed pad (the one closest to the wheel) will be dragging the rotor, so you need to get a 4mm allen wrench and back out the fixed pad adjuster a bit, so it won't rub. This bolt is probably on the backside of the caliper; you might have to work through the spokes of the wheel, or even take the wheel off to get to the adjuster bolt.

5 - at this point, the cable will be too loose, so you'll need to either tighten the barrel adjuster on the caliper (the silver screw thing at the end of the cable housing), or the adjuster on the brake lever. Turn either one or both counterclockwise. If there isn't enough adjustment left in the barrel adjusters (i.e. if they're backed out all the way), then you need to loosen the bolt that holds the cable to the caliper, and pull some more cable through.

At least that's what it looks like from here................

edit: If you need any clarification on this process, check out the Hayes manual; that's where I paraphrased my advice from. http://www.hayesdiscbrake.com/manuals/45-15216AEnglish.pdf

 

[Mudpuppy]

Ok well I got in there and fiddled with stuff.

So now its constantly rubbing like it used to.

I'll get back to you guys after I have time to turn my bike rightside up and test my brakes while riding through the dorm.

It looked like there was plenty of pad left, maybe about as thick as a nickel?

Thanks for all the help.

 

[Roasted]

That sounds a little thin...mine are at that point and I had to replace them..

 

[Mudpuppy]

My fiddling seems to have worked.

I cruised through the lobby and my rear wheel locked up easy even though I was on carpet.

My problem seems to be solved.

Thanks for all the help everyone.