Cup rear brakes. The age old 'low effort' issue.

[J.B.]

My car passed its MOT on the second attempt yesterday. On Thursday the rear brakes were at 53% efficiency, on Friday they were 60%, enough to pass. I showed them the VOSA document anyway, which they had never seen so they took a copy of it.

I thought I'd see exactly how good the rear brakes were by using the handbrake. With the handbrake fully on I was still able to drive the car along at 30mph, but it was able to slow and stop the car, it just can't lock the wheels. It also holds on a hill fine.

This can't be normal can it? The first thing I'm going to do is strip the brakes and see if they're slightly seized. Anything else I can investigate?

 

[bmh.01]

Handbrake is totally different to using the footbrake, its cable vs. hydraulic and will always be worse.

 

[Luke.]

It's all to do with that stupid compensator. I can get my cup to pass on the brake tester without fail every single time. The brakes don't need to lock to pass, they just have to meet the efficiency requirements..

Also you don't want your rear brakes to be that amazing anyway. If your trying to slow down round a corner and the rears locked before the front, your going to find yourself in a bit of a sticky situation..

A pass mark for me is sufficient enough I would leave well alone.

If your that bothered adjust the handbrake up. No more then 7 clicks and see if it makes any difference..

 

[Fred@BTM]

handbrake needs adjusting by the sound of it

 

[hilldawg172]

You should definitely be able to lock rears with the handbrake! Get it tightened lol

 

[J.B.]

Handbrake is totally different to using the footbrake, its cable vs. hydraulic and will always be worse.

Yep, I know it's chalk and cheese but my thinking was this. 60% on the footbrake is very close to an MOT fail and with the front brakes being fine it can't be hydraulics. So I think that the calipers are slightly sticky, or the rears on a cup are just this s**t, I'm not sure. A couple of years ago one of my front calipers was sticky and caused the car to fail the MOT on imbalance. Took it apart and greased, voila.

handbrake needs adjusting by the sound of it

Probably, it has to be pulled quite high to stop the car from rolling. I was in your place a couple of weeks back (leaking gearbox, my undertray is still at yours) and you commented on the amount of rust on my rears. I'll ring you about coming in this week about the leak and maybe get that seal.

A pass mark for me is sufficient enough I would leave well alone.

I do wonder if I should just leave it, but as said it barely passed and the rears are covered in thick rust. I cleared some of it by driving along with the handbrake, but not all of it.

 

[rich-6]

I managed a handbrake turn in our workshop with mine save shunting n all that, Efficiency was low on the pedal though, Which we put down to the new disks and pads.

The handbrakes a poor setup anyway, every frenchie ive had with the same rear brakes has been the same.

 

[KevF182]

Yeah, I think your right to be looking into it. I would get the discs and pads replaced, there shouldn't be corrosion of the disc face and it sounds like it will be the main problem.

Don't try and clean the corrosion off by driving with the handbrake on, there is a possibility that the piston can dislocate from the lug in the pad backing and "wedge" the pads.

 

[J.B.]

I would get the discs and pads replaced, there shouldn't be corrosion of the disc face and it sounds like it will be the main problem.

That doesn't solve the problem though. New discs and pads would help for a time, but end up the same way.