Rear brakes not good enough to pass MOT
Turbo Mini Forums

How do folks,

Right... The car has just been for an MOT and failed on the rear brakes.
It has a single line system with 4 pots on the front, a cooper s master cylinder and brand new back plates with new wheel cylinders etc so everything is moving freely and isn't seized. There are no other valves on the system anywhere apart from a bias valve which is wound all the way out to allow for full use of the rear brakes. When the bias valve is wound all the way in, it cuts off even more of the rear brakes as we watched this on the brake test rollers.

The system has been bled from the furthest away from the master cylinder to the closest in order about 6 times.

The front brakes passed no problems at all and the tester said that the pedal feels good.

The rear shoes have been set so that they catch and then returned to where they are just free of the drum.

After chatting with Rich I fitted some smaller rear cylinders but this doesn't seemed to have fixed the problem.

Does anyone have any ideas of what else I can do? Its doing my head in.

Silly question but no grease been left on inside of the drums or on the shoes? sounds silly but coukd be something silly like that

What condition are the drums in? Did you file the leading edges of the shoes?

There is no grease unfortunately, that would be a easy fix

The drums are not very old superfins (copies) that have very little wear to the braking surface...
They are the same as these on this post as the quality seems very good if not as good as the genuine ones http://www.turbominis.co.uk/forums/index.php?p=vt&tid=8942

I didn't file the leading edges of the shoes, would that help?

Edited by tomkidd on 15th Aug, 2012.

Could be the copy superfins - I had the same with mine, they really are crap.
Did the tester input the correct weight of the car? Their chart puts all Minis at 750kgs but my MK1 is only 650kgs so after altering that on his computer it passed ok

I seriously doubt it!

+1 with Paul I bet the weight is wrong for your car....

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

If you don't file the leading edge of then they can catch on the drum giving the impression that they are adjusted when they might not be.

Whats the handbrake like? If that works well it'll narrow the problems down to hydraulics/ proportioning problems.

It could be something silly like a restriction in the line eg. kinked or maybe a flare on one of the unions not formed correctly and partly blocking the line?

Edited by matty on 14th Aug, 2012.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Also, adjust the handbrake right off, then adjust the shoes to where they lock the drum and back it off 2 flats then re-adjust the handbrake

I seriously doubt it!

Make sure the shoes are installed the correct way up otherwise efficiency drops dramatically. The shoes are designed to give 'servo' action, which is why it is always easier to push a car backwards with the hand brake on, than it is forwards with the hand brake on.

Small wheel cylinders equals less brakes.

One of the items a failed on yesterday was handbrake efficiency.
It passed on the testers system which weghs the actual axle weight of the car, but not on DVLA as the weight is a fixed 750 kgs.

For the retest I shall have a bag of sand or an engine block in the boot.

Metric is for people who can't do fractions.

Hmmm... The drums were on my blue mini before and I had no issues there.

The shoes are installed correctly as I had rich at minispares check them.

The handbrake feels crap to be honest, I'm not sure whether it's user error in adjusting it.

How would I suggest we change the weight of the car? He has to go off a chart which just says 'Austin mini 780kg'

Some MOT gibbons, and that's all they are have a labotomy, put a sack if spuds in the boot and it will pass, ask the Gibbon. To set the brake machine correct!!

Edited by BENROSS on 15th Aug, 2012.

what reading did you for each wheel ?
weight in the boot wont help. if 3 or more wheels lock it will pass as long as they dont grab to lock

http://www.fishfight.net/

What mark is your car? Check the Haynes manual which will give the kerb weight - take that to the MOT with you as proof and he must change his computer, this is what I have to do

I seriously doubt it!

Did you, before you adjusted the shoes disconnect the hand brake cables at the back plates, 2 to 3 turns back from drums locked, then attach the hand brake cables, then adjust your hand brake to two or three clicks, I have the copy Finns and my brakes are good.. Alan

Main Build
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=489133

Upgrade to Turbo
http://www.turbominis.co.uk/forums/index.p...tid=448367&fr=0

As above make sure you have fitted the shoes the right way round, should look like the lining on the shoes as slipped in the direction of travel, as shown below..

Main Build
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=489133

Upgrade to Turbo
http://www.turbominis.co.uk/forums/index.p...tid=448367&fr=0

Tit at the top at the front.

Much easier to remember "the tit" than "the bit on the shoe without any friction material thusly exposing ferrous metal"

No?

V all I can say is you must of hand your hands on some strange looking tits in your time....

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Geoff

Edited by Vegard on 17th Aug, 2012.