Disc brakes losing pressure?

[Gazzab]

Not a great title for the thread but my back brake (avid juciy 5s) seems to be losing pressure ie the brake lever will sometimes go quite floppy and will require pulling right in to apply the rear brake. It will then pump back up and be fine later on. Seems to struggle when I am on a hard downhill section only! Is this bleed the system time?
Gary

[longblackcoat]

Gazzab said:

Is this bleed the system time?
Gary

Yep, as a start. I have had bad experiences of Avid Juicy brakes - sticking pistons, brakes needing repeated bleeding - but if they're in otherwise good condition, a bleed might well sort it out.

[Gazzab]

yeah I have Avid 7s on my full suss. I had to unstick the pistons on those !

[mk1fan]

A bleed should sort them out. Use 5.1 DOT fluid.

[Gazzab]

Got round to it !!! The rear seems to need more work! At the lever I couldnt stop the bubbles coming and think i got some black bits. Reckon this might be the seals? Any thoughts?

[mk1fan]

It's just the gunk that accumulates in the fluid. If taken black fluid out of one of my brakes after a few very heavy months use.

Nout to worry about.

[Gazzab]

Gave the bike a good thrashing today and the freshly bled brakes were fab! I was a little anxious on the first downhill section. Didnt want to kill myself after some bike work but I neednt of worried. They are back to rude health. Really easy job etc..