Rear Brake "spongy"

Makhaira

Makhaira

Makhaira

Soldato
Joined
23 Nov 2007
Posts
4,969
Location
Lancashire, UK
Learning about bike maintenance and symptoms continues...

Rear brake in question is a disc, cable operated, Avid BB5.

Front brake is what I would describe as tight and crisp. Runs cleanly when not engaged, then to engage there is a small movement of "slack" before the pad comes into contact, at which point there is a small amount of travel on the lever before I have "full brake" where the disc is well and truly gripped.

On the rear brake, there is quite a lot of movement post-engagement before I cannot move the lever any further. Looking at the assembly, clearances are nice and tight, and the caliper appears externally to move precisely in response to the brake lever. It's just that rather than rapidly gripping the disc it's almost like something is flexing?

Two parts to this question - do I need to pre-emptively do something given that it's the rear brake and it seems to work perfectly, just with a longer pull? Secondly, what is the issue?!

Cheers.
 
are you cables tight enough? a lot of "slack" will build up over a longer cable(aka rear) so they need to be at the right tension for it to be engage quicker.
 
are your cable outers flexing when you pull the brake lever? Check the outer is attached to the frame at all the places it should clip on - if any of the clips (they look like this) are missing, use a cable tie to fix the cable to the frame.
 
it'll just be your pads wearing down. cable disc brakes dont auto-adjust to wear like hydraulic brakes do.
You'll have an adjuster on the caliper to take up the slack.
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I've used that method and it sadly isn't foolproof (at least, not for the kind of fool I am).

If the pads are properly adjusted it's almost certainly the cable inner/outers as uv suggested. How old are they? Are they compressionless? If they're old and you can't replace them right now it could be at least worth removing the inner and spraying some gt85 into the outer. Then replace the inner and go from there.

You could also try taking the pads out completely and cleaning the caliper thoroughly. Spray it all with gt85 (wiping off/allowing to dry before adding the pads back) after cleaning.
 
Only a couple of years old with minimal mileage to date. I'll try the full stripdown, the furthest I've got in the past is adjusting the pad clearances so I've got plenty of good stuff to go at from everyone's suggestions :)
 
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