MOT- brake test on a 4wd car, how?

[Jon_Bmw]

I think I know how they do the normal brake test, but what about the handbrake? For the footbrake they take the car out and use a potentiometer?(or something like that) which measures G force in different directions, i think. Having to meet certain requirements to pass.

But for the handbrake how is it done, its the type that squeezes the pad onto the disc via the caliper(these are always a fairly crap way of doing things, but thats another story) so being 4x4 no matter how hard you pull the handbrake you'll be able to drive off fairly easily. So how do they test it, is it a visual and judgment thing?

This isn't stricly e30, but it would apply to the IX.

All the above is presuming said garage has only got a 2wd bake machine.

[Ant]

mobile decelerometer Jon, TBH if it stops, then it passes normally

nice to chat to you @ ace BTW

[dobbie82]

I thought they just put the front wheels on the rollers to check the front, and the rear wheels on the rollers for the rear. they just check that the braking is of a certain strength, but more importatly that its equal.

[Jon_Bmw]

mobile decelerometer Jon, TBH if it stops, then it passes normally

nice to chat to you @ ace BTW

Taa, couldn't think what it was called, wtf is a potentimeter then! lol

Nice to chat to you too, very nice car, very clean setup,

Will probably try and make the august german night too.

[Jon_Bmw]

I thought they just put the front wheels on the rollers to check the front, and the rear wheels on the rollers for the rear. they just check that the braking is of a certain strength, but more importatly that its equal.

exactly right...for a 2wd car, but you can't do this as it permanant 4wd and something nasty would happen!!

[dobbie82]

I thought they just put the front wheels on the rollers to check the front, and the rear wheels on the rollers for the rear. they just check that the braking is of a certain strength, but more importatly that its equal.

exactly right...for a 2wd car, but you can't do this as it permanant 4wd and something nasty would happen!!

ahhh I see! to be fair I only did 5 years of engineering college! I didnt take in much!

[Gwynleym10]

I thought they just put the front wheels on the rollers to check the front, and the rear wheels on the rollers for the rear. they just check that the braking is of a certain strength, but more importatly that its equal.

exactly right...for a 2wd car, but you can't do this as it permanant 4wd and something nasty would happen!!

Could they not jack the other wheels up? but suppose this could be interesting if it fell!

[stonesie]

I thought they just put the front wheels on the rollers to check the front, and the rear wheels on the rollers for the rear. they just check that the braking is of a certain strength, but more importatly that its equal.

exactly right...for a 2wd car, but you can't do this as it permanant 4wd and something nasty would happen!!

Could they not jack the other wheels up? but suppose this could be interesting if it fell!

No because the car moves about in the rollers as the brakes are applied so it would probably fall off the jacks.



and transfer boxes can be pricey

[Chris-W]

No handbrake test on our Range rover either - it's a transmission brake.

[maxfield]

Great question!

[Jon_Bmw]

I guess i'll find out exactly what they do with it tomorrow, its binding slightly and a pain in the arse to fix without taking off the prop and exhaust!

Chris your handbrake is connected to the drivetrain somehow then?

[Chris-W]

Chris your handbrake is connected to the drivetrain somehow then?

Here's the general idea:



A drum brake acting behind the transfer box.

[Jon_Bmw]

I found out today, they test both the footbrake and the handbrake on the little g meter thing. Footbrake got 55(units?) and the handbrake about 15(?) both passes