Very poor rear braking

[Yolandi2]

So ever since I got my Rocco the rear drums have been terrible, I've flushed the system and bled it all correctly and fitted new rear cylinders and the adjustment is fine on them, if I yank the handbrake (in a safe empty area) the rear wheels lock up so the drums and pads are working fine I just don't seem to get the pressure back there, my servo is good also

Im a bit lost on what I can try next because I haven't really needed to fix up brakes before

[james butler]

there are 2 types of rear wheel cylinder
14mm http://www.eurocarparts.com/ecp/c/Volks ... 4a7&000371
and
17mm http://www.eurocarparts.com/ecp/c/Volks ... b4c&000371
the 17mm ones will give you better rear brakes but must be used in conjunction with bias valves usually fitted under the master cylinder
also double check all your brake lines as its possible someone has jacked up the car on the lines and squashed or kinked them.

[Yolandi2]

AHH I think that might be the problem, I have bias valves fitted to the master cylinder, the new cylinders I got from eurocarparts looks more 14mm size and the ones I took off looked smaller or the two

[mark1gls]

Wrong part.
http://www.eurocarparts.com/ecp/c/Volks ... 4a7&000371

Right part.
http://www.eurocarparts.com/ecp/c/Volks ... b4c&000371

You can see the difference in size. just check they are right for your car in case I've got the wrong ones as there is 2 others listed.

The other problem could be the automatic adjuster is not working very well, the springs go weak with age, you can adjust them by jacking up the back of the car and you can just about see the end of the wedge through a bolt hole in the drum, get someone to press the brake pedal hard in the car and you get a thin screw driver and pull down on the hole in wedge.

[Yolandi2]

Definitely the wrong part then, the ones I took out and the new ones I fitted were more cylindrical at the ends instead of come shaped , I've read about the auto adjusters and copper clipped mine with new stringer springs, I can say they are definitely adjusted up ( checked through the bolt hole)

[mark1gls]

Sorry to say but it's possibly changing the rear cylinders again and rebleeding the system.
Do you still have the receipt from Euro car parts to check the part number?

[Yolandi2]

Receipt went in the bin a while ago now, not amazingly annoyed tho I think they were £5-6 each

[Yolandi2]

Ok guys fitted the new cylinders and adjusted them via screwdriver , took the car to my mates garage and had him put it on the brake tester, came out at about 43 (not sure what the units are) for the rears, he said he would be looking for 90 or higher for them to be good
What can I try next? I've checked over the lines for links or dents etc. And they're all fine, I assume the master cylinder is ok because the front ones function perfectly, maybe the bias valves? But would it be unusual for them to both fail at the same time?

[james butler]

what was the reading on the handbrake? i dont expect the rears to put much more than the handbrake.
from memory the handbrake on mine has allways been better than the brake pedal.
dont forget the rears are realistically only going to provide 20-30% of the overall braking force especially when not under load.

[Yolandi2]

He didn't try it with the handbrake but from experience putting the handbrake on hard when moving will lock both wheels, resulting in a cool, if childish, sideways side
So I assume the shoes and drum are ok?

[james butler]

i probably would do.
like i said its better to compare results of handbrake to foot brake on the rollers
you shouldn't be able to lock the rear brakes using the foot pedal but handbrake is fine.
when i checked my rears after i changed the slaves i was happy that i couldn't turn the wheel by hand with the foot brake applied which gives you an idea how little force they apply
do you still have rubber flexi hoses?
if so check they dont bulge under pressure