172 Cup rear brake effort

[Cup_Phil]

Yeah I know all about the VOSA announcement - gave it to my MOT bloke and he said he's happy to pass it with the bias valve disconnected BUT

The rear brakes are showing 18% and 31% - and from what I've read they must be about 30% on each side to pass

So even if I take it in for a retest he's saying it will fail as it's his discretion as to whether the rear brakes are working fully

Does anyone know exactly what force the rear brakes on a CUP are supposed to apply??

I read a thread on here where someone had a problem with too much braking on one side and he took the bias valve off and put a brand new one on and it was ok after that
So I'm wondering if my bias valve is seized up?

I'm considering "cheating" and just cable tying the bias valve so it applies loads more braking force to the back - but I suspect he'll just fail it then for having a cable tie holding the bias valve open lol

 

[Fred@BTM]

they can seize, grab the arm and give it a yank!

 

[LouisQ]

Cup doesnt use the rear proporting valve? There is a VOSA descrepancy note about the rear bias on 172 Cups.

 

[Fred@BTM]

yeah but a lot of MOT stations never got the note, my local ones certainly didn't, i had to get them to call up

 

[LouisQ]

But the note exists yes? So get them to give VOSA a call Phil

 

[Tom]

Yeah I know all about the VOSA announcement - gave it to my MOT bloke

??

 

[Cup_Phil]

Yeah guys - I know all about the cup bias valve and the VOSA announcement

They still use the load compensating valve but with the arm disconnected - so it stays fixed on the lowest amount of braking - that's fine - he's happy with that

But he's saying 30% and 18% isn't enough even taking into account the VOSA announcement

I don't want to try to "fix" the brakes if they aren't broken - so I was wondering if someone knows what braking force the rear brakes are supposed to apply - so that I can have it put on the rollers again and see how far out they are

 

[Sir_Dave]

Its probably as they are all seized up from lack of use. Once a week, I used to drive with the handbrake on when pulling off the drive ... keeps the pads/discs free.

Maybe try that?

 

[Cup_Phil]

Done that mate - drove around the village with the handbrake on - they were red hot lol
He says on the handbrake they are working fine - so surely that means pistons are free and discs/pads are working fine
But foot brake there is no effort

I'm very VERY tempted to cable tie the bias valve open - just so it passes - then cut the cable tie off

I was just wondering if anyone has a brake test from a PASS mot that they could scan or type the figures up - so that I know whether there really is something wrong with mine or its just the MOT tester being anal