8 replies to this topic

[lrostoke]

Anybody know anything about what the % mean on brake tests.

Sisters mini 1989 failed MOT last week, split gaitor, worn subframe mounts, and brakes

RBT service brake 49% fail
Park brake 16% fail

So we stripped both rear brakes, everything was new but checked anyway, drums, shoes, cylinders..everything working no leaks..So basically blew the dust out, readjusted..
Handbrake goes 2 clicks on lever, and holds no problem, stalls the engine trying to move it.
service brake stops straight, and works fine, pedal is good. Also checked front calipers, working fine, again they had new pads and disks 12 month ago

Take it back today and he's passed it with following

RBT service brake 51%
Park brake 14%

Park brake as gone down and service brake as hardly changed ???

[Guess-Works.com]

Nowadays the braking efficiency ( pass / fail ) is determined by the computer based on the type of vehicle, all the MOTer does is plug in the numbers and then the system decides whether it's a pass or fail.. what the algorithm is I haven't a clue, but your results suggest that its something like 50% what ever that means...

[lrostoke]

Just a bit weird, because not really anything else we could do to make the brakes better appart from upgrading them ? The MOT man said the brakes had just passed ?

Made me wonder if the smaller 12" wheels where throwing his rollers ?

[JohnGordon]

Just a bit weird, because not really anything else we could do to make the brakes better appart from upgrading them ? The MOT man said the brakes had just passed ?

Made me wonder if the smaller 12" wheels where throwing his rollers ?

I don't think the wheels will have thrown out the reading because its all down to force the brakes are applying, was the reading you have there effort or balance?

[lrostoke]

I didn't take the car for the test, but he's not mentioned balance, so I'm presuming its effort..

The weird one is the % for the park brake as gone down ???
We restored the car 12 month ago, so all the rear brakes are new, drums, shoes, cylinder, backplate, cables..
quadrants cleaned and greased.
No sign of contamination when we stripped at the weekend, everything still clean and free.
Adjusted shoes so they locked, then back off qtr turn with adjuster.

Fronts had new disks, and shoes..Calipers not seized , pistons fine, no leaks.

Good pedal, servo working fine..

When I took it for a test run, hit brakes and it stopped dead.

oh well it passed so guess its ok, just a mystery why he still moaned about them.

[JohnGordon]

I think it will be because its all new and hasn't had time to bed in yet, it usually take about 2 - 300 miles you wont notice till you really need them!

[lrostoke]

I think it will be because its all new and hasn't had time to bed in yet, it usually take about 2 - 300 miles you wont notice till you really need them!

No it was all new 12 month ago, done 8000 mile since, so nicely bedded in, and shoes have plenty of meat left on them.

Like I say they are working really good, I did a lovely skid in it testing it, scared the life out of some people stood by the road when the tyres squealed , and it stopped in a straight line, no pulls to either side.

To be honest with them working so good we aren't even going to mess with them till next year, was more a mystery why he still put an advisory about the brakes but still passed them, even though park brake was actually a lower % than when he failed it originally ?

[998dave]

Why not ask the MOT man what the percentages mean, and for more detail on your advisory.

It is part of his job to explain these things so you can fix them.

Dave

[2lrminivan]

would have been the dust making the the drum not grab on the shoes.so cleaning them out has solved that prob.also is one side was adjusted slightly more the other side would have failed as they are not the same pressure on each side.