Soft Hydraulic Brakes

[Blakey]

So a while back my rear brake started to stop working properly. I figured it was worn brake pads, so I started a thread about it, and bought some new pads and fitted them. Now, that has improved the response a tiny bit but the rear brake is still virtually doing nothing.

My brake set up is:

Am I at the stage of having to get them bled? Is this something I should even consider doing myself (it appears like it's going to be a tough job)? Is there anything I can do to confirm/disprove they need bleeding?

Thanks in advance for any pointers,
Blakey

 

[Mikerb]

To state the obvious if the brake is not capable of stopping the back wheel then the caliper pistons are not grabbing the rotor. So your first check should be to do a visual check to see if the pistons both move. It could be that one or even both pistons are seized in which case you need to free them up. Your brakes need bleeding if you detect the following:-
The lever slowly keeps moving towards the bars/grip if you hold it on with pressure.
The distance before the grab point of the brake increases if you pump the lever ( ie repeatedly apply and release).
Both are signs that air or moisture has got into the fluid.
Bleeding the brakes is no big deal. You need to buy a kit ( try the EPIC SRAM brake kit...it comes with full instructions).

If neither of the above conditions is the case then your pads and/or the rotor are hopelessly contaminated, so you will need to clean the rotor and fit new pads.

 

[Blakey]

Thanks @Mikerb. I'll have a look at the pistons as that sounds like it might be the issue. Since changing the pads the rear brake does work a bit now (I can even get it to lock the back wheel and skid in the wet), but it's definitely not as solid as day one. The front brake lever has not changed - it has the same bite position and same feel of a strong application as it has always had, and as the rear used to feel like.

Great suggestions on how to check for brakes needing bleeding. I'll also check them out.

Thanks again - advice is greatly appreciated.

Cheers
Blakey

 

[Al Boneta]

If the pistons are not retracting back into their piston bores, the piston seals are probably dry and the pistons need to be cleaned.
A quick and easy way method involves cotton swabs and brake fluid.
Remove the wheel and then remove the pads.
Take a pad spacer and stick it in the caliper.
Squeeze the lever until the pistons make contact with the pad spacer.
Dip a cotton swab in some Dot 5.1 brake fluid and clean the cylindrical part of the pistons.
You'll probably use more than a few cotton swabs before they stop turning black.
Press the pistons all the way back into the bores.
Clean the inside of caliper with isopropyl alcohol
Install old pads and a pad spacer.
Squeeze the lever to see if the pistons still stick
If they still sick repeat the previous steps until they don't.
Once they are freed up install new pads.
If you don't feel like reading this, watch this video that's the same basic principle