MOT place tried to fail my car on left/right brake bias – When I asked them how they knew this because I didn’t see a 4 wheel rolling road they said they tested it on a 2 wheel road. I explained that being perm 4wd this can damage the transmission and any damage caused I would be expecting them to pay for.

I said there is nothing wrong with the brakes, and that the VOSA process for any perm 4wd car is to do a road test and see if it pulls left or right. As mine doesn’t they agreed to pass it.

I should bloody well hope so. Don't mess with my car.

Oh and they slipped in that this wouldn't qualify as a free re-test if I took it away to do the work!

Riverway MOT Centre Trowbridge - Steer clear! 

Presumably in Neutral it should be OK on the rollers?

Gary

Sure you didnt let them off lightly Dan.

So when i MOT mine i have to find a place with a 4 wheel roller to test the brakes?

edit; seen gaz reply now, neutral ok? 2004 black Vogue TD6

No, neutral is NOT ok...

Your front and rear wheels are always connected via the centre diff, just like left to right, what gear your in has no relevence to the "final drive" section.

I have a copy of the page from the worksop manual to give him for future reference. 

just spoke to my boy [mot tester] and he says that you can use a de-accelerometer to test the RR brakes..


this might be useful to someone.. http://www.motuk.co.uk/manual/contents.htm ... - .- -.




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Last edited by stan on 27th Jan 2011 5:31pm. Edited 1 time in total

Dan: So is the damage done straight away? If so have you noticed anything or did they not even put it on the rollers?

scarey wrote:

just spoke to my boy [mot tester] and he says that you can use a de-accelerometer to test the RR brakes..


this might be useful to someone.. http://www.motuk.co.uk/manual/contents.htm

Vehicles not to be tested on a roller brake tester:

Certain vehicles should not be tested on a roller brake tester, e.g. vehicles with

· More than one driving axle permanently engaged

· Limited-slip differential

It's quite simple, the front and rear wheels are always connected. This is the reason you cant tow it with two wheels in the air.

The workshop manual basically says the same as the VOSA info above.

The thing that muddies the water is that the car can be tested on a 2 wheel rolling road IF the propshaft to the axle being tested is removed. Obviously this does not happen in an MOT.

Considering a road test is an acceptable method for testing, I see no reason for the RR to go anywhere near a rolling road.

On top of this, this is also how garages test the Handbrake - another surefire way to screw your tranny if left on for more than a second or two. 

I think Scarey meant a road test using a hand held de-accelerometer....

Gazellio wrote:

I think Scarey meant a road test using a hand held de-accelerometer....

Ah, in which case sorry, that would be fine

Jsb wrote:

Dan: So is the damage done straight away? If so have you noticed anything or did they not even put it on the rollers?

No damage detected, however I will be reporting them to VOSA for trying to screw me with the free re-test thing! 

So glad that the guy that does our MOTs knows his stuff! He used to MOT my 911 Carrera 4. I had similar problems with that car and MOT garages until my friend recommended his mechanic. Reformed

Taken from Scareys link:

The Testers Manual

3.7 Brake Performance (Roller Brake Test)

Vehicles not to be tested on a roller brake tester
Certain vehicles should not be tested on a roller brake tester, e.g. vehicles with

· More than one driving axle permanently engaged

· Limited-slip differential

· Belt-driven transmission

· Brakes for which the servo operates only when the vehicle is moving

These vehicles should be tested using a properly calibrated and maintained decelerometer or a plate brake tester designated as acceptable for the statutory tests, see Sub-Section 3.7B and C.

A roller brake test is also not appropriate for vehicles with damaged, under-inflated or studded tyres.

B. Decelerometer Test

1. If the vehicle is of a type which cannot be tested on a roller brake tester,

· set up the decelerometer in the vehicle in accordance with the equipment manufacturer’s instructions

· drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and note the brake efficiency recorded when applying only

a. the service brake.

b. the parking brake.

c. while the vehicle is decelerating under the action of the service brake note if the steering wheel tends to pull or the vehicle tends to swerve.

Record the appropriate results of the brake test via the VTS Device. Where the VTS Device is unserviceable see the Introduction section paragraph 3.

By service brake - do they mean the foot brake? 

yes

RE: the Limited slip differential, that would explain why my old Accord Type R didn't get put on the rollers for the front brake test. I always wondered why, I thought he was cutting corners  2006 Mercedes CLS
1991 Retro-style Mini
But really finding it hard to fight the urge for a S/C...

DAN, i did mean on a road test as GAZ suggested [ta gaz ] its just i didnt listen to my boy properly.. ... - .- -.




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