Spongy brakes

big_chris-2

Before I hit Cannock yesterday my brakes ('09 XT discs) felt solid, lever kicked in about 1/3 of the way through the lever travel and all was good.

I did the full 15 mile loop and there are some sections which require heavy braking (mostly due to my lack of skill - and 15 stone!) and both brakes now feel spongy, the rear lever especially pulls way past half way before it bites. I've checked the pads and there's plenty of life left, I can't imagine I killed them on one ride? I've been around that course a few times in much worse weather and never had this issue. It was bone dry up there, and quite dusty.

nicklouse

spongy is air in the system. give them a bleed.

bet you boiled the fluid.

Kerguelen

If the brake feel is now spongy it's possible that, as nicklouse points out, that you have boiled the brake fluid.

Unfortunately, brake fluid never fully recovers its original boiling point after that kind of treatment and you may well find that the only solution is to replace the fluid.

big_chris-2

Hmmmm... bugger. With that and the forks now leaking oil from the right seal, it was a pretty expensive trip!

There's one section which is very steep and you basically have to sit on the back wheel the whole way down. By the end of this I'd been on both brakes the whole way and they started to feel iffy after that, so I guess you're right.

Not something I really want to tackle myself (I know some say it's easy but I can mess up just about anything with a spanner in my hand) so off to the LBS it is I guess

big_chris-2

Out of interest, how do I stop this happening again in future? The obvious answer is to brake less or not weigh as much, but neither of those are going to happen!

Is there a more rubust brake fluid I can bleed them with?

nicklouse

correct.
no.
bigger discs.

or change to a braking system that does not use mineral oil.