Hi all - a little help, please?
The nice people at Biketart sent me some formula mega brakes in replacement for some Avids that were not right. All very good so far.
However, the front brake won't actually brake, as in the pads don't apply any pressure to the disc. There's no contact point adjustment that I can see, and I've bled them (twice). The pads move, but they're just too far apart to brake the wheel.
Would Formula discs be wider than the Avids that are on the bike, or is something wrong? I've obviously mailed Biketart, who have been more than helpful (not to mention generous) so far, but I'd like to fix this today if possible.
There's also the slimmest possibility that I'm being a numpty...
sticky pistons. Pump 'em a few times with the wheel out watching to make sure the pistons don't pop right out. Work 'em in and out a few times
The movement in braking action the piston does not move thru the seal - the seal deforms and moves with the piston - its only when taking up slack / free play the piston actually moves thru the seal.
Maybe lube the pistons / seals with the correct brake fluid for the brake
When I've used other brand discs with my Formula brakes in the past they didn't perform as well - loads more lever travel.
I couldn't be bothered to measure the discs thickness but came to the conclusion that Formula discs are indeed thicker than Magura and Hope ones so the same may be true for Avid discs.
As above you could try removing the wheel and gently applying the brakes to move the pistons out a little more.
Thanks both - Makes perfect sense about the pistons stuck to the seals. I've taken the wheel out, and the lever stops before getting far enough to free the pistons up, so it may be that my bleeding technique isn't what it could be!
Assume that lubing the pistons is a relatively simple matter of removing the pads, then putting a drip of DOT4 around the edge of the piston? I've tried that, and will see if they free up.
Then I'll try bleeding them again - not the easiest thing in the world with these, is it!
Thanks again
Hmmm - sounds like yo may well have air in them then. with the wheel out they should move.
They move a bit, and it's even both sides, just not very far. Less than a millimeter each pad/piston. I'll give 'em another bleed!
try bleeding them with a very worn set of pads so you can get more fluid in them than you need, then you should be able to let it out when you put then new pads in, to the right bite point you need.