Limited slip diff - any good?

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EspritSE

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Nov 1, 2010
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34
Location
Fife
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C32 & C63 AMG
Hello all,

I've owned a C32 for 9 years and am now thinking of buying a M156 engined car.

I have a quick question.

I notice some people are recommending a car with a Limited Slip Diff to improve traction. Would I be correct that an LSD has little/zero effect on traction if your traction control is switched on?

Thanks in advance for any responses/clarification.
 
It will have an effect with the TC on. With an open diff the wheel with the least grip will spin up. The TC will take the throttle away until the wheel stops spinning. With a limited slip diff the drive is shared equally between the driven wheels. Therefore the grip on the road is effectively doubled. You’ll get twice the traction before a wheel starts to spin. You will certainly notice better launch with than without, even with TC switched on
 
One of my previous cars had lsd from factory (Honda Accord type r) and although I cant comment on traction control on or off as it never had that option I can confidently say grip alone was night and difference to a friends Honda Civic type r non lsd car, If the options there and funds allow id put an lsd on any car I highly recommend them.
 
Put good tyres on and then unless you are a very hard driver you won't miss it.
 
Put good tyres on and then unless you are a very hard driver you won't miss it.
Yeah thats true mind works in straight race mood all the time, regular driving i guess its not necessary
 
Put good tyres on and then unless you are a very hard driver you won't miss it.
Yes and no. Quite a lot of power/ torque with the M156, you'd definitely notice it in normal driving when wet, pulling out of junctions or just accelerating moderately hard from low speeds. But admittedly you're unlikely to miss it except for this 0.1% of the time if you don't drive hard.
 
It will have an effect with the TC on. With an open diff the wheel with the least grip will spin up. The TC will take the throttle away until the wheel stops spinning.
In addition to cutting the throttle, the ESP stability control will apply brake to a spinning wheel which is why the rear pads and discs take a hammering.
Put good tyres on and then unless you are a very hard driver you won't miss it.
While good tyres are an absolute must, my experience was that an LSD or torque biasing diff. delivers a massive improvement in driveability in less-than-perfect grip conditions even under moderate acceleration. I'll be honest that I was also surprised at how much difference it made in hard straight line acceleration on dry tarmac - something I put down to much reducing, or totally eliminating, silent TC/ESP intervention under those conditions.
 
Red, red and amber....dunno what comes next, gone by then!
I’d say advisable if you have the cash and want to play, but not for normal day to day driving.
 
Thanks for your replies,

I understand the basics of how an LSD works, I had one years ago on an Alfa 75 without traction control. My experience was I found it more prone to fishtailing in damp conditions as drive swapped from side to side as I was trying to scoop it all up (nothing to do with my driving ability :)). I've had a few RWD cars (Ford Capri, Triumph 2000, Rover SD1, Alfetta GTV6, Lotus Esprit) without traction control and an open diff and I found them easier to control than the 75 with LSD.

Of course traction control/stability control takes care of all that. You can floor it halfway round a 90 degree bend in the wet, the rear of the car skips to the side 9" and with virtually no steering correction the car squats down and tears along the road making you look like a hero.

So if I had a car with an LSD I'd be keeping the TC on all the time, unless I was struggling to get moving in snow in which case the LSD would make a big difference.

I'm probably overthinking this but I can't help think that the TC will cut in and reduce power (apply brake?) before the LSD has a chance to be of benefit.
 
I'm probably overthinking this but I can't help think that the TC will cut in and reduce power (apply brake?) before the LSD has a chance to be of benefit.
Yes, you're overthinking it.

I've had M157-engined W212's with the factory AMG Locking diff (a traditional plate LSD), a Quaife Torque Biasing diff and a regular open diff. The open diff was (predictably) the one that exercised the TC/ESP most. Both the AMG and Quaife diffs worked in harmony with the TC, with much reduced intervention due to the lower propensity for one wheel to lose traction and spin up.

In my opinion (others may disagree) for road use, of the three, the Quaife was the most refined and best suited.
 
Both the AMG and Quaife diffs worked in harmony with the TC, with much reduced intervention due to the lower propensity for one wheel to lose traction and spin up.
Ok thanks,

What I take from that is that there is a percentage slip before the TC cuts in, the LSD is preventing the slipping wheel reaching that threshold because of the drive on the other wheel.

I'm happy now. :)
 
Of course traction control/stability control takes care of all that. You can floor it halfway round a 90 degree bend in the wet, the rear of the car skips to the side 9" and with virtually no steering correction the car squats down and tears along the road making you look like a hero.
Not sure i agree with this. If you've activated traction control, the car won't squat down and go, as power will be cut. So you're just left looking silly as you slow down and can't accelerate. I'd argue the LSD DOES have the effect of helping you round a corner though. You can obviously make it fishtail if you're too over zealous.
I'm probably overthinking this but I can't help think that the TC will cut in and reduce power (apply brake?) before the LSD has a chance to be of benefit.
No. Even when on, the TC control allows a very small amount of wheel spin, i.e. the LSD will be working well long before the TC intervenes. TC is the middle (sport) setting seems a good balance in the 212.
 
What I take from that is that there is a percentage slip before the TC cuts in, the LSD is preventing the slipping wheel reaching that threshold because of the drive on the other wheel.
Spot on.
 
The best Modification you can have, i totally agree with Phil :thumb:
 
So if I had a car with an LSD I'd be keeping the TC on all the time, unless I was struggling to get moving in snow in which case the LSD would make a big difference.
Not necessarily. If you go for the (probable) Quaife then it's torque biasing nature can still spin up one wheel if there's no traction and thus there is no torque to 'bias' to the other wheel.
A torque biasing diff will deliver typically 4-5 times the torque to the wheel with more traction than the wheel with less traction. Five times zero is zero. A torque biasing diff must have at least some traction on the lesser able wheel to work.

Check out the above for accuracy if you really want an LSD to help in snow but I think the above describes what happens with a torque biasing diff. For absolute traction in snow a speed sensitive diff is required but they are less liked in day to day driving. A full 'locker' can be a mixed blessing in snow. Trying to reverse uphill with both rear wheels spinning an zero lateral traction will have the plot swapping ends pretty swiftly.
 
I have had a Quaife fitted to my 507 Coupe since ownership and the driving experience is much improved. It is not going to stop any issues if I was to smash the throttle into the carpet with the steering at any sort of angle but when accelerating hard from a standing start, or applying the throttle firmly out of a corner the higher level of grip is very noticeable. As mentioned above for normal day to day driving you almost certainly won't notice it but it will work when you need it to :thumb:
 
If you go for the (probable) Quaife then it's torque biasing nature can still spin up one wheel if there's no traction and thus there is no torque to 'bias' to the other wheel.
A torque biasing diff will deliver typically 4-5 times the torque to the wheel with more traction than the wheel with less traction. Five times zero is zero. A torque biasing diff must have at least some traction on the lesser able wheel to work.
^ Absolutely correct.

This is the main argument put forward against the Quaife ATB diff and in favour of a regular plate type LSD, or the Wavetrac hybrid ATB diff. However, in practice the number of times during UK road use that a Quaife ATB diff is disadvantaged tends to zero, especially if winter tyres are fitted in winter conditions.
 
^ Absolutely correct.

This is the main argument put forward against the Quaife ATB diff and in favour of a regular plate type LSD, or the Wavetrac hybrid ATB diff. However, in practice the number of times during UK road use that a Quaife ATB diff is disadvantaged tends to zero, especially if winter tyres are fitted in winter conditions.
Glad I got the torque biasing bit right!
Just depends on what the OP means by 'struggling to get moving in snow'. In day to day out on the roads not a big deal as you say. Getting off a driveway in Scotland - can be make or break. If he has the latter type of scenario in mind, better he knows if he's not already aware - hence mentioning it.
 
Presumably the LSD will go the way of the Dodo with EVs having separate motors per wheel?
 
Presumably the LSD will go the way of the Dodo with EVs having separate motors per wheel?
When individual wheel motors are used there's no (mechanical) differential at all.
 

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