Rear hydraulic brake always spongy

Rodders30

Hi all,

I've had my bike a while now and I guess its about time I sorted the rear brake.
Ever since I have had it, its been spongy. I bought the bike mail order so didnt want all the hassel of sending bits back etc...

So I re bleed it by pumping/releasing the bleed nipple etc... and its still bad. I tie wrapped the brake lever to the handle bar over night with the reservoir cap off, but made no improvement.
I have bleed from the caliper with a syringe.
I have pushed the pots fully back in and bleed.
I have taken the caliper off and had it up so its the highest point and bled. I've held it in all different angle and bled.

Its still spongy, lol. I cant think of anything else? Dodgy seal in the master cyclinder? Theres no leaks on the system.
Front brake is fine. Pics attached.

I think its shimano deore M555 ?

Pics attached.

nicklouse

So what are the pads doing to the rotor?

Have you bedded it in again?

Rodders30

Pads and rotor are fine. The brake is powerful enough to lock the wheel, its just spongy.
Typical 'air in system' feel, but I cannot get any air out.

allthegearnoidea

this May sound a bit daft, but are both of your levels the same distance out from the bars??? my rear hope was always a different feel to the front, hadnt noticed it was quite a bit closer to the bar to start with than the front!

Rodders30

Yes, both exactly the same

allthegearnoidea

Was Worth a try! ;-)

Rodders30

Yea, im up for trying anything as I have no idea now, lol

nicklouse

Rodders30 wrote:

Pads and rotor are fine. The brake is powerful enough to lock the wheel, its just spongy.
Typical 'air in system' feel, but I cannot get any air out.

Yes not what I am asking.

When applying the brake watch the rotor. Does it get deflected? This is one of the most common reasons fr a spongy feel lever.

cycleclinic

Nick is pointing to centering the caliper around the disc. Depending on the mounting system used this is either easy or requires thin shims.

Rodders30

When I do the caliper up I:

Leave bolts loose on caliper (finger tight)
Pump up brake and hold to align caliper centre to rotor
Do up bolts
Release brake.

I have no rotor warp and it doesnt rub the pads when I rotake the wheel.

mister p

That method doesn't always work unfortunately. Pull the lever and see if the rotor deflects as the brake pads hit it. Then loosen the bolts and move the calliper the opposite way to the deflection by the amount the disc has moved. Tighten and try again. The aim is to get no deflection in the rotor. It may take a few goes to get it bang on but when you do the brakes feel great.

nicklouse

Rodders30 wrote:

When I do the caliper up I:

Leave bolts loose on caliper (finger tight)
Pump up brake and hold to align caliper centre to rotor
Do up bolts
Release brake.

I have no rotor warp and it doesnt rub the pads when I rotake the wheel.

yes but is the rotor being moved by the pads?
yes or no?

if yes do as above. if no then we need to look at other possiblities such as there is actually some air still in the system or you have a damaged hose or........

Rodders30

Hey all,

Whilst checking the rotor, which maybe had 1/4mm movement, I've tweaked this also, I had a thought. A while ago at work a mate had this on his motorbike, so I checked the lever and found the problem, photo attached! screw not adjusted properly! DOH!! school boy error, lol. :oops:

Now they both are the same!

allthegearnoidea

This was what I was asking much higher up! ;-)

Rodders30

Lol, yea, by eye they looked spot on, but in reality no! Shoulda measured accuratly!