them's the brakes...

October 12, 2009 1:16 AM

I've just changed the disc brake pads on my bicycle and now the calipers won't 'grab' onto the metal disc enough to brake effectively...

...the calipers still seem to move correctly, but I noticed a fluid leak when I pushed the callipers into the forks and I've lost a lot (but not all) of the pressure in my brake lever.

i'm running a shimano slx disc brake system and would very much like to fix this myself: my local bike shop will take at least a week before they can do the repair and I'm loathe to be without my bike for that long. can anyone offer any advice?

I'm guessing the either the system needs bleeding, or the seals need replacing...?

thanks in advance!

posted by hairgelburrito to Sports, Hobbies, & Recreation (4 answers total)

The Park Tool website is a pretty good resource. They have a page on servicing Shimano hydraulic brakes. And while I'm not sure they're using the exact same model as yours, I would imagine that the differences would be minor.

Any lost fluid will almost certainly have to be replaced to get them working again.
posted by le morte de bea arthur at 1:44 AM on October 12, 2009

I'd agree that a seal check / replace and a bleed sounds like it should sort things out.

SLX brake bleed instructions

My biggest bit of advice on bleeding would be to read the instructions on doing it about 5 times more than you think you need to before starting, as once you're into it it can feel like a job that needs 2+1/2 hands . . .
posted by protorp at 2:52 AM on October 12, 2009

You need to fix the brake fluid / seal problem first, but once you've got that sorted out...

Wear gloves so you don't get greasy fingerprints on your brake rotors, the skin oils will gunk up your brake pads and reduce brake grip.
posted by anthill at 10:00 AM on October 12, 2009

Air in the line will act exactly this way (a leak in the system certainly could have caused this).
Air is compressible, when you get on the brakes hard, you are putting a lot of work into compressing that air. Bleeding the line (and refilling the system if necessary) should solve this problem handily.
posted by milqman at 1:42 PM on October 12, 2009