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Rolling roads and LSD's?


Arran

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Afternoon all

 

Just had my mate ring me up and tell me that his E46 M3 diff has started whining etc on the way back from pod last weekend. I said to him before he went on the dyno that there is speculation about rolling roads messing with the LSD, sure enough when he came off the dyno the dash was lit up like a christmas tree and then on the way home was making noise. The reason I ask is when I get the Uprev done it was be dynod several times and I slightly anxious as to what it will do to the diff

 

What's the deal with this guys?

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Abbey don't have a rolling road.

They have a system that spins the hubs.

If you go onto there Facebook page you will see that Mark

uploaded a full demonstration in video format a few days ago.

You will be safe there and no doubt answer you question in due course.

Fear not young Arran your diff is in safe hands.

:lol:

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The rolling road for testing brakes can damage the diff.

 

 

Yes, it's possible but as long as you make The M.O.T tester aware that your car has an LSD there shouldn't be any problem. A diligent tester will bring up on his computer any special requirements for the car he is testing anyway. Now then, my mate owned and ran an M.O.T garage for over 30 years and he told me that he only used the Tapley for vehicles with permanently engaged 4wd. For cars with LSD's he simply ran the test with both rollers running. He said that using a Tapley for a road test is pretty worthless as this only gives you an overall braking efficiency test on all 4 wheels whereas running on a rolling road (with both rollers running) gives the tester a lot more information on the rear brakes :shrug: .

 

 

Pete

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Just ask the MOT tester to road test the car, rather than putting it on the rolling road. Thats what I did and I was more than happy for him to go for a spin round the block. If he was a 19yr old trainee on the other hand I would have taken my car else where :lol:

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The rolling road for testing brakes can damage the diff.

 

 

Yes, it's possible but as long as you make The M.O.T tester aware that your car has an LSD there shouldn't be any problem. A diligent tester will bring up on his computer any special requirements for the car he is testing anyway. Now then, my mate owned and ran an M.O.T garage for over 30 years and he told me that he only used the Tapley for vehicles with permanently engaged 4wd. For cars with LSD's he simply ran the test with both rollers running. He said that using a Tapley for a road test is pretty worthless as this only gives you an overall braking efficiency test on all 4 wheels whereas running on a rolling road (with both rollers running) gives the tester a lot more information on the rear brakes :shrug: .

 

 

Pete

 

:thumbs:

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Il be taking it to a friends garage or my work for the mot, will just get them to road test it tbh, not worth the aggro doing my thoughts in :lol:

 

M3s do have LSDs yes, the E46 has what's called an M active differential, slightly different to a normal LSD. Quite fragile though along with their boot floors (quite common for them to tear)

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Chaps, a Rolling Road isnt the same as the brake tester on the MoT. The former is not a problem at all, the latter can have issues with LSD's (and is hilarious with a locked diff) though but MoT testers know this.

The fact that M3owners havent reported there is an issue would suggest this is a one off. :)

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Chaps, a Rolling Road isnt the same as the brake tester on the MoT. The former is not a problem at all, the latter can have issues with LSD's (and is hilarious with a locked diff) though but MoT testers know this.

The fact that M3owners havent reported there is an issue would suggest this is a one off. :)

This.

 

The only thing you will get with the RR as reported above is that the dash will light up like a Christmas tree and the car may go into a limp/snow mode was it detects the rear wheels spinning and fronts not. Anyone that has taken a RWD car to the dyno will tell you that the lights tend to go out when you drive the car down the road. Its certainly what happened in my 350z. I dont remember it in the 370z as Mark went to "test" his mapping work on the road :drive1:lol:

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