Page 1 of 1

Help: Front disc pads rubbing

Posted: 2 Jan 2008, 10:00am
by natmat
Hello all,

Problem: disc brake pads are always rubbing (rather than just brushing) on the disc, so it's like cycling with the brakes on.

I'm running a front LX hydraulic disc on my commuter bike and its pads are now persistently rubbing on the disc.

I've tried recentering the wheel in the forks (Kona project IIs), but pads still too close. The disc isn't bent/warped, the pads are reasonably worn, so surely there should be a greater gap.

My guess is that it's due to the pistons not returning into their housing after being deployed. In which case, how I clean them to correct this problem?

I've already cleaned around the pistons and squirted a bit of WD40 around the pistons, but that didn't seem to help the situation. Do the pistons come out?

I hope someone can offer some help, because at the moment even free-wheeling is hard work ;)

Nathan.

Posted: 2 Jan 2008, 11:17am
by tobyj
I had this problem. Depending on the system (this works for Deore XT) you could try:

On the bracket that attaches the brake to the fork you will see two bolts*. Loosen these bolts and turn the wheel. It should turn better. Operate the brake on / off a few time on the disc then carefully retighten the two bolts. This should centre the brake caliper on the disc.

* These are NOT the bolts that hold the whole ensemble to the fork (these are the other two bolts you will see).

Don't forget to retighten the bolts!

Good luck..

Toby

Posted: 2 Jan 2008, 11:29am
by natmat
tobyj wrote:Loosen these bolts and turn the wheel. It should turn better. Operate the brake on / off a few time on the disc then carefully retighten the two bolts. This should centre the brake caliper on the disc.


Thanks Toby, I'll give it a try later today and report back.

Posted: 2 Jan 2008, 11:44am
by Auchmill
There's some info on the Park Tool website, which may help. I'm not sure that pistons should be sprayed with WD or anything else. I seem to remember when doing car brake pads many moons ago it mentioned using brake fluid as a lubricant if necessary.

Posted: 2 Jan 2008, 5:12pm
by natmat
Thanks for link, very useful indeed.

As for oiling the pistons, I hope I haven't now done any damage to the oil seals... only time will tell. But, to be honest the amount of grit, diesel, oil, petrol, salt and slime with which they were previously coated I hope the 'few' drops of oil I applied will cause more damage that this winter has already caused.

Posted: 2 Jan 2008, 11:14pm
by andyml
natmat,

not sure how old your bike is or how well it was built but a professional build would/could include facing the caliper mounts with a special tool to ensure proper alignment....

you could ask any cytech qualified mechanic to do this for u with the special tool

brgds andy :)

Posted: 2 Jan 2008, 11:31pm
by natmat
Problem solved!!!

Thank you tobyj for solution and Auchmill for link to pictures/additional-details. Just completed in 30 seconds and I now have my disc re-aligned perfectly between pads (well, pads aligned to disc).

Since this is the first disc brake I've owned, I guess I should have read the leaflet more thoroughly when I installed them. After 3 months use, the last 2 months have been progressively more hard work as I've been fighting against the every-increasing persistent braking resistance... and I thought it was the cold weather slowing me down ;)

And, the added bonus is that I seemed to have gained an extra 2mph on my commuting average, great!

Thanks everyone, job well done.

Nathan.

ps. Oh, andml, FYI I built this complete bike (including wheels) myself and I like to think it was/is well built. But, I've learnt something extra today and so it's now built better.