Rear Brake Balance Mot Fail

[Jon Green]

Hi all,

 

After three years laid up I've finally got my 2B back on the road... almost!

 

MOT test was today and It failed. Not much really but my back brake drums are out of balance by a lot. nearside = 150 Offside = 235

 

Apparently on monday this wouldn't have been a failure but new rules mean it is.

 

I've looked at both drums and to be honest they both have new shoes, new disks and leak free cylinders. The only thing I did spot was that the wheel cylinders are slightly different. The offside cylinder was changed at the last mot (4 years ago) due to a leaky cylinder.

 

 

Is there a chance that the wheel cylinders mismatch is causing the imbalance or are they all the same inside? I'm clueless on hydraulics.

 

Thanks

Jon

[Guest Ian & Carole]

In a word YES!!!

Start afresh and buy 2 new cylinders fit them and give them a good run with one foot on the throttle and one on the brake pedal.

[Guest chris brown]

If the cylinders are the same size then it may be one piston seized but to be on the safe side do as Ian advices change them both

[Jon Green]

Doing a little more research identifying the wheel cylinders I have... the offside (235) cylinder is from the sierra estate and the near side a saloon.

 

As my front brake force was coming in at about 160 per side would you recommend using the estate cylinders and having strong back braking force or the saloon?

 

I guess locking the back wheels before the front isn't good and therefore the saloon cylinder would keep a better balance all round.

[Snapperpaul]

You want less at the back or you will spin

Sierras had a brake proportioning valve to prevent rear lockup

 

[theduck]

Less at the back

[biksz]

use saloon cylinders on the back change them both so they are the same then you no what is what with the back brakes front brakes shoud do 75% of the braking and the rear 25% of the braking hth

[Jon Green]

Both changed now. Imbalance was due to a sticky piston.

 

Thanks for the help as always!

 

Jon