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Brake testing?


steve_d
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The RR has permanent 4 wheel drive but there is a differential between front and back.

Is it possible to test the brakes using MOT brake testing rollers where only one axle is on the rollers?

My Dakar will be going for SVA soon and they would ideally want to find brake efficiency for each axle and each wheel. If they have to use the Tapley Meter it will only give overall brake performance.

Many thanks

Steve

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The RR has permanent 4 wheel drive but there is a differential between front and back.

Is it possible to test the brakes using MOT brake testing rollers where only one axle is on the rollers?

My Dakar will be going for SVA soon and they would ideally want to find brake efficiency for each axle and each wheel. If they have to use the Tapley Meter it will only give overall brake performance.

Many thanks

Steve

Yes,the garage I bought my 110 from & they MOT it, does 1 axle at a time, no props removed either,hasn't caused my 110 any problems, just put the transfer box & main gearbox in neutral, then the rollers turn the wheels not the engine/transmission.

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Yes,the garage I bought my 110 from & they MOT it, does 1 axle at a time, no props removed either,hasn't caused my 110 any problems, just put the transfer box & main gearbox in neutral, then the rollers turn the wheels not the engine/transmission.

Same as this my garage MOT's loads of LR 4x4s and does them 1 axle ata time without taking props off.

Once told a garage that my Series 1 V8 was perm 4x4 as old drums don't pull straight. The garage had a floor mounted test system using some mechanical method and sat a frightend apprentice in the passenger seat.

1955 LR

V8

no roof

no door tops

no seatbelts

told me to drive rather quickly towards a row of new cars and hit the brakes!

Poor bloke s%*t himself but it passed :P

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Yes,the garage I bought my 110 from & they MOT it, does 1 axle at a time, no props removed either,hasn't caused my 110 any problems, just put the transfer box & main gearbox in neutral, then the rollers turn the wheels not the engine/transmission.

But it's still running the centre differential at a higher speed than Land Rover recommend.

If they bothered to read the VSI (Vehicle specific information) displayed when they log the vehicle in, they would see that a permanent 4wd Land Rover is NOT suitable for roller brake testing.

With a centre diff in good condition and for the short period it's on the brake tester then no, it probably wont do any immediate damage. With a worn diff, and on a continued basis, they're chancing it. If they do go ahead, and damage the transmission then the garage will be liable for the cost of repairs.

Over speeding the centre diff wears the internal thrust washers, this causes poor mesh between the sun and planet gears.

The result is clunky transmission and eventual failure/broken gear teeth.

This does not happen immediately , it's a gradual process.

Next time it's in for an MOT, ask them to print off a copy of the VSI. Then ask them why they are still sticking on the rollers.

It's either ignorance, or laziness because they cant be bothered to pop a tapley meter in and run it up the road.

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But it's still running the centre differential at a higher speed than Land Rover recommend.

If they bothered to read the VSI (Vehicle specific information) displayed when they log the vehicle in, they would see that a permanent 4wd Land Rover is NOT suitable for roller brake testing.

With a centre diff in good condition and for the short period it's on the brake tester then no, it probably wont do any immediate damage. With a worn diff, and on a continued basis, they're chancing it. If they do go ahead, and damage the transmission then the garage will be liable for the cost of repairs.

Over speeding the centre diff wears the internal thrust washers, this causes poor mesh between the sun and planet gears.

The result is clunky transmission and eventual failure/broken gear teeth.

This does not happen immediately , it's a gradual process.

Next time it's in for an MOT, ask them to print off a copy of the VSI. Then ask them why they are still sticking on the rollers.

It's either ignorance, or laziness because they cant be bothered to pop a tapley meter in and run it up the road.

Your garage should do a road test with a tapley meter that measures the deceleration and will not wind up the transmission. No full time four wheel drive should be put on brake testing rollers damage will ensue

:(

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We always test Land Rovers on the brake tester.

I dont think it turns quick enough to wind the transmission up. It says in the Land Rover manual I think, that it is suitable to do so aslong as the wheel doesn't exceed 5km/h.

Certain four wheel drive cars cannot, such as a new Jaguar we tested the other day, as it has the part time 4wd. The 4wd only works when the ECU senses that the front wheels are turning at a differnt speed to the rear ( fed by the ABS sensor) and supplies drive to the rear wheels.

Our brake tester also has an option to test the transmission brake.

Mick

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We always test Land Rovers on the brake tester.

I dont think it turns quick enough to wind the transmission up. It says in the Land Rover manual I think, that it is suitable to do so aslong as the wheel doesn't exceed 5km/h.

Certain four wheel drive cars cannot, such as a new Jaguar we tested the other day, as it has the part time 4wd. The 4wd only works when the ECU senses that the front wheels are turning at a differnt speed to the rear ( fed by the ABS sensor) and supplies drive to the rear wheels.

Our brake tester also has an option to test the transmission brake.

Mick

The transmission wont wind up, it's overspeeding the centre diff that's the problem.

You're absolutely correct, Land Rover do say up to 5Km/h is OK, I think brake rollers top out about 4 or 5 MPH.

Not much in it i know, but...If the VSI states the vehicle is unsuitable for roller testing and something goes bang when you do, the testing garage is liable. And there is always the potential to do harm that's not immediately apparent

We repaired a Suzuki Ignis 4grip last year that had been put on the rollers at another garage, the bill was in four figures.

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Hi,

Forgive my ignorance, but aren't there two different issues here?

I have never owned or worked on a defender, but I think that they have a lockable centre diff right(?) and hence this can be left unlocked for the test. The risk of over speeding this diff is something I can't comment on.

The Range Rover on the other hand (as mentioned in the original question) has a centre diff with a viscous coupling unit and so, assuming this is working, I would think that it can not be tested one axle at a time since the VCU would apply significant torque to the other axle which would probably result in it climbing out of the rollers even before putting the brakes on..

It's a few years now since my RRC was near a test centre, but last time it was they certainly took it for a drive to do the brake test - I didn't see them put anything in it though, what do these Tapley meters look like?

Roger

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Hi,

Forgive my ignorance, but aren't there two different issues here?

I have never owned or worked on a defender, but I think that they have a lockable centre diff right(?) and hence this can be left unlocked for the test. The risk of over speeding this diff is something I can't comment on.

The Range Rover on the other hand (as mentioned in the original question) has a centre diff with a viscous coupling unit and so, assuming this is working, I would think that it can not be tested one axle at a time since the VCU would apply significant torque to the other axle which would probably result in it climbing out of the rollers even before putting the brakes on..

It's a few years now since my RRC was near a test centre, but last time it was they certainly took it for a drive to do the brake test - I didn't see them put anything in it though, what do these Tapley meters look like?

Roger

All COIL sprung Land Rovers have permanent 4wd. They have a centre differential to allow variations in axle speed during on road cornering. The centre diff would only be locked where this would cause loss of traction, ie off road.

So yes, the diff is normally left unlocked.

The problem is, when brake testing on rollers, one axle is stationary whilst the other can run up to 4 or 5 mph, this speed differential is taken up in the centre diff, land Rover recommend that this speed is no higher than 5KH/H.

If the manufacturer recommends not to brake test on rollers, as does VOSA via the vehicle specific information contained in the MOT computer database, then any tester who does, leaves themselves liable SHOULD damage occur.

The viscous coupling transfer box only came in with 1990 model year Range Rovers, all previous models had a manually lockable centre diff. These will climb out of the rollers as you say.

A tapley meter is a decelerometer, it measure the rate of retardation when the brakes are applied, then gives a print out as a % efficiency. This is entered into the MOT computer in a separate box from where normal roller test readings would go.

The one Les put up is a modern digital one, the older ones were about a foot square and looked a bit like a ships compass.

Put in the passenger footwell, zeroed, then up the road 15-20mph brakes on. Take a reading. They will also measure brake imbalance as they can detect the vehicle slewing sideways under braking.

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I'm with Mr. Pending on this one. No garage that I have ever used has put my Land Rovers on the rollers for the brake test, and in fact, one garage said he couldn't do the mot because he couldn't put it on the rollers.

Mo

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Not sure where you're going here Western.

Earlier you posted that you had no problems with your Land Rover being roller tested.

Now what you post up clearly states that Land Rovers are unsuitable for roller testing.

Yes, if you remove a propshaft and lock the diff, then the issue is avoided.

But...in the context of an MOT, where NO dismantling is allowed, the answer is in the text, don't.

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just making the workshop manual info available & saying that LR isjust protecting itself from any claims that could result from not carrying out the test to the book.

as for my 110, it will be tested as it always has been, & as you say MOT test doesn't allow any dismantling.

Yes, if you remove a propshaft and lock the diff,

maunal extract says transfer box & centre diff & main gearbox in neutral

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just making the workshop manual info available & saying that LR isjust protecting itself from any claims that could result from not carrying out the test to the book.

as for my 110, it will be tested as it always has been, & as you say MOT test doesn't allow any dismantling.

maunal extract says transfer box & centre diff & main gearbox in neutral

Same as mine Ralph. I've used the same garage for about the last 18 years - my 110 has been tested on the rollers for since I've had it (7 years) and the Range Rover prior to that (about 6 years). The rollers rotate at about 3km/h - nowhere near fast enough to cause any issues at all.

Matt

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just making the workshop manual info available & saying that LR isjust protecting itself from any claims that could result from not carrying out the test to the book.

as for my 110, it will be tested as it always has been, & as you say MOT test doesn't allow any dismantling.

maunal extract says transfer box & centre diff & main gearbox in neutral

Actually it doesn't mention the diff lock, just says main and transfer boxes in neutral.

With both boxes in neutral and a prop off it wouldn't really matter if the diff was locked or not.

The rollers on a brake tester definitely run faster than the 5kh/h Land Rover recommend, I've done enough MOTs in my time.

If you or any MOT tester is happy to go against the advice of both the manufacturer and VOSA, then fair enough.

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Well I use the same MOT station as my daughter does for her Discovery. The garage where I have work done uses the same place.

When I had the Range Rover they took it out and used the Tapley Meter.

A few years ago I was aked to drive it onto the rollers.

Why I saked aren't you using the Tapley meter.

"Because we have this new roller brake tester that can do perminant four wheel drive, that's why.

So far I've not had a problem

mike

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