Calculating rear braking effort. MOT Fail. (172 Cup)

[Hoaxy]

I had the cup MOT'd earlier at Renault and the car failed due to the rear brakes recording "little or no effort".

I'm aware that this is a common problem and have access to the VOSA document, however does anyone know what percentages at the rear would constitute as a fail? Or is it calculated as a total overall breaking figure? (A minimum of 50% or something) :S

I've done a search, and although everyone states that the load sensor is redundant and the bias valve is set at a low value etc, I still can't see any figures - what percentages are we talking?

Also, the percentages were not printed on the MOT Refusal. I asked and was told that they didn't know them - it had just failed. Surely that's not normal, they should be noted somewhere right?

 

[cliobritt]

theres a thread on here somwhere, search.

 

[Fred@BTM]

shout at renault UK, it'll pass, surprised a main dealer dosn't know about it

 

[Hoaxy]

Britt - I've searched and there's no detailed information regarding percentages.

I read somewhere about a 80/20 split, but is that the standard factory percentage? Is that the minimum pass requirement? Is that even a true figure?

Fred - I intend to tomorrow; hence, I'd like some rough percentages just to cement my point.

 

[Dean.]

There definately should be a sticky made for this, Admins?

 

[Matt W]

Just shout loudly at the tester.

 

[Craig Ed]

http://www.dft.gov.uk/vosa/repository/MoT Issue 31 - Apr 2006.pdf

Page 8.

 

[ben lee]

the minimum percentage is 50% for all four wheels and 16% for parking brake but is different if a wheel locks up.

a tester can fail a brake for little or no effort even if it passes the 50%.

 

[Hoaxy]

Thanks Ben, it's appreciated. Is the 50% an average of all four?

For example:

Front o/s = 90, n/s = 90
Rear o/s = 18, n/s = 20

Average of all four = 54.5% = pass

Also, you say that a tester can still fail it even if it hits 50%.. how so?

 

[Hoaxy]

Oh, and craig, that's the VOSA document that I already have. I appreciate the help though mate.

 

[Hoaxy]

Bit of an update:

I've just spoken with VOSA and they have given me the total braking figures quoted by Renault as 52%

So, surely that's a pass?

I have no figures for the rears alone, but based on reading the VOSA pdf, given that they are actually functioning (not reading at 0%) then its a pass, no?

Can anyone clarify this?