Car just passed her MOT, but, what do the braking figures mean?

[StephenFord]

An hour ago my 17 year old car passed her MOT, not even an advisory! Can anyone explain to me what the 'braking' figures actually mean? Last year I had a 'service brake' efficiency of 76% and 'parking brake' of 17%. After some money spent, this year was a 'service brake' of 87%, and 'parking brake' of 30%

But what does that mean??

[mickywrx]

It means your hand brake is a bit crap, but, your foot brake is alright.

You could take it elsewhere and get different reading though, it all depends on the tester and brake rollers.

[StephenFord]

3 minutes ago, mickywrx said:

It means your hand brake is a bit crap, but, your foot brake is alright.

 

When handbrake was 17%, yes, it was a bit crap, but now at 30%, I can stop on the steepest hill without drama - what is it 30% of?

[jmurray01]

I never trust MOT brake tests, aside from identifying binds and imbalances, they are next to useless.

As said above, depends on the MOT tester and equipment also, with handbrake some pull it tighter than others therefore getting a better/worse result and same with the service (foot) brake.  My mother's Focus has a crap handbrake (which I was certain would have failed) but it passed with no advisories, yet unless you pull it on far harder than my mother would/could, it won't hold on a hill without being in gear.  Go figure!

[StephenFord]

1 minute ago, jmurray01 said:

As said above, depends on the MOT tester and equipment ...

I'm in Northern Ireland, all our MOT centers are government run, so you can't just pop to another garage LOL I still have no idea what the %age figure means...

[mickywrx]

3 minutes ago, StephenFord said:

When handbrake was 17%, yes, it was a bit crap, but now at 30%, I can stop on the steepest hill without drama - what is it 30% of?

30% of overall braking efficiency within the tested components, I "think".

[jmurray01]

Just now, StephenFord said:

I'm in Northern Ireland, all our MOT centers are government run, so you can't just pop to another garage LOL I still have no idea what the %age figure means...

I can't answer that question, but personally I'd go by feel.  If you pull it on at low speeds and it stops well and holds on hills without being yanked all the way up, I'd say it is alright.

Perhaps someone can give an answer on the percentage though which I'd also be curious to know truth be told.

[StephenFord]

1 minute ago, mickywrx said:

30% of overall braking efficiency within the tested components, I "think".

LOL that is a meaning without a definition, so, you don't know either then 🤣

[mickywrx]

Just now, StephenFord said:

LOL that is a meaning without a definition, so, you don't know either then 🤣

I can show you any amount of brake tests from MOT's for the trucks we run at work.

Some pass the brake test, some fail the brake test, but, all pass the MOT.  All the MOT's are carried out by Vosa.  As above, go figure. 😕

[StephenFord]

2 minutes ago, mickywrx said:

I can show you any amount of brake tests from MOT's for the trucks we run at work.
 

Micky, with respect, that is NOT the question I asked. My car passed the MOT, that is simply not the issue. I really would like to know what the %age figure quoted on the certificate means. Hopefully @unofixor @tomfocuswill be along in a bit...

[F0CUE]

16 minutes ago, StephenFord said:

Micky, with respect, that is NOT the question I asked. My car passed the MOT, that is simply not the issue. I really would like to know what the %age figure quoted on the certificate means. Hopefully @unofixor @tomfocuswill be along in a bit...

It means they have a certain percentage based on their machines to test what power the brakes have. Drum brakes only use a small amount of power when you brake. When using the handbrake it uses as much percent depending on the cable and adjustment of the adjusters (how far they are adjusted). New shoes and a new cable with the adjusters back to the start would probably never gain 100% as I am sure they use the values based on braking but may be wrong. So 30% is a pass and if it holding well I wouldn't worry about it.

[mickywrx]

35 minutes ago, StephenFord said:

Micky, with respect, that is NOT the question I asked. My car passed the MOT, that is simply not the issue. I really would like to know what the %age figure quoted on the certificate means. Hopefully @unofixor @tomfocuswill be along in a bit...

When anyone says "with respect", it's not meant that way. Hey ho. 🙂😉 

That one passed an MOT last week, but, supposedly the brake test was a fail.  😕

 

[StephenFord]

2 minutes ago, mickywrx said:

When anyone says "with respect", it's not meant that way. Hey ho. 🙂😉 

That one passed an MOT last week, but, supposedly the brake test was a fail.  😕

 

I have absolutely NO idea why you are showing me a bit of paper with %ages on it?? I already have one when the MOT tester gave me my own pass certificate. If you could take a breath...... I wanted to know WHAT the %ages meant, not how they are written down on a form 🤣

[unofix]

Brake % is the amount of force being applied to stop the rolling road. Each rolling road in an MOT station will be calibrated so that each testing station should be the same within the tolerances allowed.

In a prefect world a brake would apply sufficient force that the rolling road would be locked solid and totally unable to move. This would = 100%

If there was zero braking force or restriction to the rolling road then the brake force would = 0%

A service brake (foot brake) reading of 87% is very good. The roller is being stopped with a force approaching total lock.

A Parking brake (handbrake) reading of 30% is fair. The roller is being held with a force that is about a third of what it would take to totally lock the rolling road completely.

Sorry, but that's best I can think to explain how it's measured. Hope it helps a little.

 

[StephenFord]

I just googled the NI MOT web site and have found the following:

Brakes testing criteria

Any one of the following points about brake performance will result in a vehicle being refused a certificate:

• The service brake efficiency is below 50 per cent (58 per cent for cars first used on or after 1 January 2012)
• The parking brake (hand brake) efficiency is below 16 per cent

So, last year my handbrake passed by just 1% (I knew it was rubbish), quite an improvement this year getting 30% (14% more than a fail rate)

[isetta]

Section 1.2.2 of mot manual explains how it is worked out. I don’t just mean what the pass and fail thresholds are,  it also explains a bit more about it. If you really want to know

[TomsFocus]

13 hours ago, StephenFord said:

 Hopefully ... @tomfocuswill be along in a bit...

That poor guy must get so many tags...  

30% on a cable handbrake is pretty impressive.  They're not designed to apply much force (unlike the hydraulic system) so will never be anywhere near 100%.  

[StephenFord]

40 minutes ago, TomsFocus said:

That poor guy must get so many tags...  

30% on a cable handbrake is pretty impressive.  They're not designed to apply much force (unlike the hydraulic system) so will never be anywhere near 100%.  

I got my brakes refurbed after my last MOT, new discs, pads, drums, shoes etc. To be fair, the braking on this car now is so much better than I ever managed to get on my old Celica GT4! I have never had one single roll back after 4 x clicks on the steepest of hills!