Torsen and MOT brake tests

[20Vcqdriver]

Having just finished my 6 speed and 3B project I am about to take the car for an MOT. Is it safe to carry out the normal brake tests on the car (fronts turning rears stationary etc) or will it have to have the box on the passenger seat and be driven down the road to test brake efficiency!? Know this is not a problem on non torsen quattros but not sure about the Torsen version. Thanks

[ericd]

from experience, each Mot station/tester do it differently , depending on whether it's a large dealership or a private garage, and most importantly whether they know they're dealing with a 4wd car/system, been in the car doing the brake test with the dynometer/gmeter box or whatever you wanna call it, I think you'll find it rarer and rarer to find places that do that though...

[Rusty]

My mechanic chap seemed to think it was OK to do the test on the brake tester providing he was quick!

[stiglet]

Absolute no no!! Not only is it likely to bust your torsen but it could also roll of the test rollers into a hard object!

My local MOT guy drove it into the car park, locked up all 4, then returned saying "that'll do, son". I was happy with that.

[quattronutter]

my mot man put a new jag on the rollers yesterday.....bye bye gearbox

[S2central.net]

The Jag has Torsen centre dunnit ?

On the UK mainland I have always had my MOT brake test done with the g-force test widget on the floor during an actual road test (round the car park).

In NI, the brake test machine is a two-wheeled affair but is smart enough to run in opposite directions during the test so that zero torque is transferred up t'other end.

In saying all that - all the factory info I have says that 2-wheel brake tester is OK for use up to a certain speed - 15km/h rings a vague bell.

Paul

[HPmuirt]

Absolute no no!! Not only is it likely to bust your torsen but it could also roll of the test rollers into a hard object!

Sorry stiglet, but IMHO that is utter tosh!

This has been debated to death on here and too many people believe that a few seconds on the rollers will burst their torsens, yet I would suggest that every car on this forum has been MOT'd several if not many times on a standard 2WD brake tester. My 13 year old car has been tested 10 times.

The tests are carried out at 4MPH which is significantly less that the differential speed between the 2 axles if you spin up or skid the front wheels. How many cars do we know of that have had torsens fail at all, let alone during a 4MPH brake test?

Also, all main steelers in my area use standard brake test rollers and not all are the reverse wheel type Paul mentions. Are they all wrong?

Finally, whilst a G-meter will show that the car can stop, it will not show with the same accuracy the actual braking capacity at each corner and therefore highlight any potential issues....something I would definately want to know.

Please prove me wrong if anyone has hard evidence, otherwise let's put this ridiculous myth to bed....where are the MythBusters when you need them?

Cheers n

Si

[stiglet]

Fair enough, but everything i've read proves otherwise. I can definately back up the car rolling off the rollers though, as this did happen to mine when testing the rear brakes (or so my mechanic said first time he tried it).

Does it not at the very least strain the torsen? The moment you put the brakes on, that acts as a torque differential so surely the torsen would be active? I don't know about the low speeds, wasn't aware of that.

EDIT: No, now that i think about it i am completely wrong! I remember reading somewhere torsens don't have any effect under braking, only when accelerating?

My bad!

[Keeper of The Kitten]

Remember that it is a differential, and that no matter how much you might try to prevent it, the front and rear wheels turn at different speeds when you negotiate corners (or indeed if the tyres at one end are more worn than the other).

If you drove round in circles for about 25 miles non stop you might hurt it (note: I don't think so), but I really don't think a few seconds on rollers will kill a torsen - I'd be upset if they're as weak as that.

They are designed to allow the front and rear outputs to turn at different speeds - as it happens, 0mph and 4mph are different speeds in exactly the same proportion as 60mph and 64mph.

[s2driveruk]

mines been done at VAG dealers on the brake tester the last few times without issue and i have been assured of no probs with 'old' quattros Actually i think its less stressfull than some mot guy launching your car from their premises while u sit in the waiting area and they go with the g-meter thingy!!!!

[dubmeister]

As an MOT tester I don't test any permanent 4wd vehicles on the rollers- you aren't even supposed to test cars with traction control on them.- when you try and get the car off the rollers with TC it just bogs down, and will not allow the car to drive off until you disable it. With permanent 4wd cars they give slightly false readings on the rollers and the 4wd /diff/?? causes the car to lurch from side to side! I've seen boys test 4wd cars and the noises from the centre diff don't sound too good!!

Remember- if your car blows up/overheats/ dies while being tested that's YOUR problem - you allowed it to be tested, you try taking the station to court after they have blown your car up!!
Beware!!
Make sure the tester uses the Tapley meter(or equiv) to test the brakes- most testers are testers 'cos they are crap mechanics!!!!

This is what it says in the manual:

http://www.motuk.co.uk/manual_370.htm

[Fat Audi 80]

Mine is always done with the box on the floor and my Tester launching the car up and down his very small car park!

It keeps the numpties amused as they think he has lost the plot!

Cheers,

Steve.

[HPmuirt]

Mine is always done with the box on the floor and my Tester launching the car up and down his very small car park!

It keeps the numpties amused as they think he has lost the plot!

Cheers,

Steve.

And everyone is worried about breaking the torsen or the car jumping off the rollers

What about the tester crashing the car or damaging something as he launches? Remember that far more people on this forum have lost gearboxes though launching than have lost torsens through MOT brake tests on rollers. In fact I still maintain that NONE of our cars have lost a torsen due to an MOT.

cheers n

Si

[Error404]

also the owners manual states you can tow one axle for up to 30miles at a max of 30mph....

[PeteRR]

The S2 is having its MoT today and so I quizzed the guy about how he'll go about the brake test. He said he'll use a deccelerometer as he's not allowed to use the brake roller on 4wd cars like these (Though he did say some of the big 4x4's are ok on the rollers).

Ok by me I thought, just hope she passes now.....