Binding Avid brakes

[geomark]

Have just pulled a bike out of storage for a year and the back Avid disc brakes are binding horribly.  Have stripped them, checked the pads, checked the alignment etc but no joy, it is as though the gap between pads has reduced or piston not returning properly and they are binding the whole time.

 

Any suggestions on what else to try or possible causes?

[Baaisikilist]

Possible that the air particles in the dot fluid have expanded and increased the pressure. I'd recommend a re-bleed...

[geomark]

Ok thanks, pity, was hoping for an easier solution for holiday bike maintainance  .....oh well

[David Marshall]

It is most likely that the piston seals in the caliper are sticking.  Try removing the caliper from the bike, remove the pads and carefully press the brake lever with something like a cone spanner between the pistons to get the pistons as far out as you can.  Make sure they come out evenly otherwise one may pop out completely.  Give the whole thing a good wash and allow to dry fully. Lube the pistons with dot fluid and push them back in.  If that does not work you probably need to replace the seals.

[Eddie Stafford]

Exactly the same thing happened to a friend’s bike that is equipped with Avid 1 brakes. After struggling to get the brake calipers off the rotors, I took the brake pads out and pushed the levers to get the pistons to stick out a bit.  I then took the caliper apart and pulled the pistons out.  What I found was that the DOT fluid in the caliper behind the pistons was semi crystalized.  I cleaned it all out, sparyed it with silicon and put everything backed together and will bleed the brakes this weekend.  Depending on the result I either stuffed it up or managed to fix it.

[geomark]

It is most likely that the piston seals in the caliper are sticking.  Try removing the caliper from the bike, remove the pads and carefully press the brake lever with something like a cone spanner between the pistons to get the pistons as far out as you can.  Make sure they come out evenly otherwise one may pop out completely.  Give the whole thing a good wash and allow to dry fully. Lube the pistons with dot fluid and push them back in.  If that does not work you probably need to replace the seals.

Thanks David, will try that and if not probably replace the brake with something else as this bike only gets used 3 weeks a year and don't want to go through this mission yearly at the start of each holiday. Is it just Avid that is especially prone to this?

[geomark]

Exactly the same thing happened to a friend’s bike that is equipped with Avid 1 brakes. After struggling to get the brake calipers off the rotors, I took the brake pads out and pushed the levers to get the pistons to stick out a bit.  I then took the caliper apart and pulled the pistons out.  What I found was that the DOT fluid in the caliper behind the pistons was semi crystalized.  I cleaned it all out, sparyed it with silicon and put everything backed together and will bleed the brakes this weekend.  Depending on the result I either stuffed it up or managed to fix it.

Lets hope it's the latter, good luck!

[igg]

On a related note, can anyone tell me if brake dust will corrode seals?

 

I had a sticky piston on my XT brakes so I could never get them centered. I lubed the hell out of the piston last night (using shimano mineral oil) and I'm happy to say my brakes are now centering and not rubbing. But it seems the process of lubing them has allowed brake dust to migrate past the seals into the caliper/brake lines as the fluid has turned black. The brakes are rock solid though.

 

Also, are XT calipers serviceable? i.e. replace seals, etc..

[David Marshall]

Thanks David, will try that and if not probably replace the brake with something else as this bike only gets used 3 weeks a year and don't want to go through this mission yearly at the start of each holiday. Is it just Avid that is especially prone to this?

I'll get shot down by the Avid fans, but in my book any Shimano (even the cheapest) is better.  The Avid kit is around R200 per caliper + labour so you may as well get the Chain Reaction special and be done with it.

[JXV]

 

 

Is it just Avid that is especially prone to this?

Avid and SRAM brakes use DOT fluid which is susceptible to absorbing water and causing corrosion. Brakes that use a mineral oil (like Shimano) might be better for a bike that stands a lot because the oil will resist corrosion and does not absorb moisture.

 

Avid also makes acceptably decent cable actuated disc brakes.

[Skylark]

My sister has an an ancient bike with budget avids on it, stands around for months with no action, gets zero maintenance and the brakes are amazing - the front are almost the sharpest brakes I've ridden. Don't understand it but the bike is around 10yrs old.

[geomark]

Stripped the calipers out, pistons seem to be running fine and clean.  Don't have a bleed kit here so just released one of the bleed screws slightly and removed a bit of fluid to relieve pressure and working ok now.  They are a little but under pressure and will need bleeding (next year!) but it seems air bubbles or similar in the systemhad expanded as er Baaisikilist' suggestion.