Arran Posted September 22, 2012 Share Posted September 22, 2012 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? Quote Link to comment Share on other sites More sharing options...
4RE Leather Posted September 22, 2012 Share Posted September 22, 2012 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. Quote Link to comment Share on other sites More sharing options...
glrnet Posted September 22, 2012 Share Posted September 22, 2012 +1 What Pete said ^ Quote Link to comment Share on other sites More sharing options...
Arran Posted September 22, 2012 Author Share Posted September 22, 2012 Il take a look the video pete, glad that puts my thoughts at ease, my mates is definatley ****ed Quote Link to comment Share on other sites More sharing options...
glrnet Posted September 22, 2012 Share Posted September 22, 2012 Il take a look the video pete, glad that puts my thoughts at ease, my mates is definatley **** Can't say I blame him, you'd expect the rolling road people to know what they are doing Quote Link to comment Share on other sites More sharing options...
Dblock Posted September 22, 2012 Share Posted September 22, 2012 The rolling road for testing brakes can damage the diff. Quote Link to comment Share on other sites More sharing options...
Chris AME Posted September 22, 2012 Share Posted September 22, 2012 its to do with how brake tester rolling roads put a load into the diff, as far as i know the type on a dyno should be fine as there is no load forcing the diff to turn Quote Link to comment Share on other sites More sharing options...
4RE Leather Posted September 22, 2012 Share Posted September 22, 2012 Just based on this theory then, Could a over zealous MOT tester bust it ! Like Halfords Test stations? Quote Link to comment Share on other sites More sharing options...
Dblock Posted September 22, 2012 Share Posted September 22, 2012 Do m3's have lsd's? Quote Link to comment Share on other sites More sharing options...
Ekona Posted September 22, 2012 Share Posted September 22, 2012 On some cars, if the rear wheels are turning but the fronts aren't then it can put the car into limp mode, as it tries to protect the drivetrain because it thinks you're revving the car whilst it's stuck in snow or mud. Quote Link to comment Share on other sites More sharing options...
Dblock Posted September 22, 2012 Share Posted September 22, 2012 Just based on this theory then, Could a over zealous MOT tester bust it ! Like Halfords Test stations? Halfords test station in my city is still the same staff as the old garage before Halfords took over. Good staff. Quote Link to comment Share on other sites More sharing options...
JetSet Posted September 23, 2012 Share Posted September 23, 2012 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 . Pete Quote Link to comment Share on other sites More sharing options...
DoogyRev Posted September 23, 2012 Share Posted September 23, 2012 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 Quote Link to comment Share on other sites More sharing options...
4RE Leather Posted September 23, 2012 Share Posted September 23, 2012 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 . Pete Quote Link to comment Share on other sites More sharing options...
Arran Posted September 23, 2012 Author Share Posted September 23, 2012 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 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) Quote Link to comment Share on other sites More sharing options...
docwra Posted September 24, 2012 Share Posted September 24, 2012 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. Quote Link to comment Share on other sites More sharing options...
Chris`I Posted September 24, 2012 Share Posted September 24, 2012 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 Quote Link to comment Share on other sites More sharing options...
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