Cable Disc brakes - rear one keeps "fading". Advice needed.

[al Mossah]

Hi all,

I recently got a Giant Yukon MTB with Hayes cable disc brakes, and would
like the benefit of URC's wisdom.

Initially both brakes were fine. Then, after a couple of weeks it was as
if the combination of rear disk and pads was coated with a special
zero-friction coating. The front brake remained very good. I took out the
rear pads and cleaned off any dirt. No change. I took the pads out and
cleaned the disc with meths. Replaced pads, and the friction was reduced
still further, if that was possible.

Thinking that I needed to isolate the problem to the disk or the pads, I
swapped the pads over with the front pair. Result: Both brakes worked well
for a couple of weeks.

Now the rear one has "faded again", i.e. when I apply full pressure, it
slows down the bike, but it only takes a slight downward slope and the rear
brake cannot bring the bike to a halt. Even on a dry dirt path it has
difficulty locking up.

I've adjusted them according to the Hayes instructions. The amount of
travel before the moving pad hits touches the disk is very small; the brake
lever is not pulling far enough back to touch the handlebar.

I'm about to repeat the swapping of pads, but wondered if anyone had had a
similar experience. If I ever end up with both front and back mis-behaving
at the same time, then I will die.

Peter.

 

[Paul Boyd]

al Mossah said the following on 29/06/2006 21:49:
> Hi all,
>
> I recently got a Giant Yukon MTB with Hayes cable disc brakes, and would
> like the benefit of URC's wisdom.
>
> Initially both brakes were fine. Then, after a couple of weeks it was as
> if the combination of rear disk and pads was coated with a special
> zero-friction coating. The front brake remained very good. I took out the
> rear pads and cleaned off any dirt. No change. I took the pads out and
> cleaned the disc with meths. Replaced pads, and the friction was reduced
> still further, if that was possible.

I don't think meths should have been used - on Shimano discs they
recommend IPA (Isopropyl Alcohol, not India Pale Ale!). I guess Hayes
might be similar. It does sound like oil or grease contamination - have
you been spraying oil on your chain or cassette? The mist can drift
around if you're not careful. Or used an incompatible bike cleaner?

I think you have two options:

1 - chuck away all four pads and buy new (you've probably just
contaminated the fronts by putting them on the back.) Clean the rotors
up with IPA and refit the new pads. Keep them scrupulously clean - not
even a fingerprint on the rotor. I don't know about Hayes brakes, but
make sure (if it's an option) that you get the right pads for the rotors
you have. Once pads have absorbed contaminant, they're dead, but rotors
can be cleaned.

2 - if the above hasn't worked, do what I've done and chuck away the
cable discs and replace with hydraulic. All comments about cleanliness
still apply, but my reasoning is that cable discs are always the budget
end of the market, so they may simply not be as effective as hydraulics.

--
Paul Boyd
http://www.paul-boyd.co.uk/