XT785 brake problem.

I’ve had a problematic rear brake for a while now, asked about it a while ago on here and was given the diagnosis of contamination. Which was unlikely but I couldn’t rule it out.

Since then when I use the bike (it’s not my main bike) almost every time the rear brake has no bite to it, been through discs and pad change outs including make and compounds, brake disc cleaners, bleeds and rebleeds. The rear needs a hefty pull to lock the wheel up (not back to the bars) whereas the front brake is perfect and would quite easily put me over the bars with half the force used on the rear. It is a little more spongy than the front but I had put this down to hose length.

I am ruling out contamination, I have three bikes which get treated/cleaned/maintained identically but this is the only brake I ever have problems with. Sometimes it is adequate but not great, next time it useless.

Any ideas? Was about to buy a new one but I like to mend and fettle with things.

Cheers

Sonnyjim

Faulty master cylinder would be my guess.

Is this in the lever?

Cheers

Sonnyjim

I am ruling out contamination

I wouldn’t just yet – my front 785 weeped oil where the hose joined the calliper causing it. LBS sorted it so I’m afraid I can’t remember what exactly they swapped to fix it.

Thanks brass neck, I had thought about that but presumed I would loose pressure in the system, this is never the case. I will have a very close look at this tomorrow though. Probably a seal at the banjo fitting or the fitting its self.

Cheers

Edit. Clean disc and another new set of pads in today made little difference, so oil had no time to weep onto pads.