I had a realisation today that I'll be away working when the MOT runs out so managed to get a slot at a garage I've never used before. I dropped off the RRS and went to do a few things and when I came back I saw the RRS on the ramps from the viewing area - I'd never watched an MOT before.

Anyway I noticed the rollers so asked the bloke at the desk how they did the brake test on 4x4's and he replied by decelerometer on a road test - all good I thought. I was busy playing a game with my son on his tablet when after a bit the desk bloke asked me if the RRS had selectable 2/4 wheel drive - nope, fixed 4x4....then I noticed it on the rollers. The fronts were just finished and was moving forward to do the rears, so I asked the bloke to ask the tester not to continue as I'd heard it can cause damage. He was politely told to ' off' and the rears were done - I wasn't too happy, but it passed the MOT with no issue's.

I didn't notice any issue's or sounds on the drive home so I'm hoping all is ok, but what potential damage could actually be done, and would it already be broke? 13MY Range Rover Sport Autobiography SDV6 - mine
14MY Range Rover Evoque Dynamic SD4 Black Pack - wife's
99MY Defender 90 TD5, Soft Top Conversion - my toy, and bairns favourite

Cant see how you can check brakes on an mot rig as it will not stay in the rollers it would drive itself out so on way were th brakes checked properly

I've just had my car get its French MOT (control technique...which lasts for 2 years.. yay) and when they do the brake tests they put a frame of free rolling rollers under the wheels not on the road rollers. I have never had a 4 x 4 have an english MOT so have never seen them tested any other way. Mine passed and not noticed any problem or difference with braking since. Never argue with stupid people, they will drag you down to their level and then beat you with experience.

Watch this YouTube clip

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 Never argue with stupid people, they will drag you down to their level and then beat you with experience.

You cannot test the brakes on the rollers for a vehicle that is in constant 4 wheel drive,,you have to use a Decelerometer,,on some 4x4’s you can test the park brake in the rollers.

Andy. Andy.
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Well hopefully he was just bluffing then, going through the motions to look the part?

I did see the fronts turning and rears still (could only see the passenger side so no idea if rotating opposite ways), but I'm not sure how fast things went as it was just the end I noticed. The rears were turning with fronts still, but again I never noticed if they went fast as I was asking the desk bloke what he'd said. Apparently he was told that some work, some don't and this one was working...

So are these rollers powered? I assume the are as I can't see any other way to drive them with a fixed 4x4, with rears stationary. 13MY Range Rover Sport Autobiography SDV6 - mine
14MY Range Rover Evoque Dynamic SD4 Black Pack - wife's
99MY Defender 90 TD5, Soft Top Conversion - my toy, and bairns favourite

Brit Plumber wrote:

Watch this YouTube clip

Some mot rolling roads have 4x4 function where it turns the wheels in the rollers in opposite directions. This stops the prop from turning as it is just working the open diff.
But as far as I am aware range rover sports have open centre diffs so turning the front wheels or back wheels the same way would just work the diff.
Freelanders however where the rear wheels run directly off the front diff cannot be done this way and must be run using the first method of turning the wheels in opposite directions.
Discovery 2 park brakes can only be tested using a decelormeter .
If the car for example has Ltd slip diffs then it also must be tested with a decelormeter
Rich

thanks for some sensible input Rich

rich_sargie wrote:

But as far as I am aware range rover sports have open centre diffs so turning the front wheels or back wheels the same way would just work the diff.
Freelanders however where the rear wheels run directly off the front diff cannot be done this way and must be run using the first method of turning the wheels in opposite directions.

Thats good news then, all I'd previously heard, and read on other posts here was that fixed 4x4's should not be tested on rollers.

Thanks for the info.  13MY Range Rover Sport Autobiography SDV6 - mine
14MY Range Rover Evoque Dynamic SD4 Black Pack - wife's
99MY Defender 90 TD5, Soft Top Conversion - my toy, and bairns favourite

When I had my Scooby I made the tester take it on the road to test the brakes....never even thought when I took the Sport the other week  Steve.

Your Scooby had a Ltd slip diffs so would not be able to be brake tested, if a vehicle has a locking or Ltd slip or viscous coupling centre diff then the wheels must be rotated in opposite directions. If the vehicle has Ltd slip or locking front or rear diffs then it must be tested using a decelormeter . If the vehicle has open diffs them it doesn't matter. Also to add electric locking diffs or just open diffs with a locking mechanism so can be tested normally

Ahhhh  Steve.