LSD- what does it actually do....in non tech speak?

[laz11]

I have a 4.3 Griff which I love driving hard when conditions permit especially in the twisties. Now it has Nitrons and has been set up well so it feels very secure, grippy and confidence inspiring and although I am no driving god I do feel the sensation when it loses grip and starts to go into understeer and oversteer and I can play around with that at the lower limits. So I am curious to know the effects that the LSD has on the handling of the car and how I might notice it coming into play....and maybe the pro's and con's of having one fitted...in basic easy to understand non techie speak?
Cheers
Lawrence

[Ryder35]

A limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity

HTH

[thegman]

Ryder35 said:

Wikipedia

It basically means that if one wheel loses traction, the other will remain powered. This isn't what happens with a normal diff - in that case all power goes to the wheel which has lost traction. This is crap if trying to corner very fast or in the wet.

Edited by thegman on Tuesday 30th December 14:16

[Ryder35]

What it "actually does" is help with traction out of corners etc by (AFAIK) allowing the wheel that has traction to turn even when the wheel that does not is slipping. For example if you had a RWD car with one rear wheel in the air and one on the ground with a normal diff the wheel in the air would spin but the one on the ground would not move. With an LSD they would both move.

I think that it it anyway, but I could be wrong!

[grumbledoak]

When you go around a corner, the outside wheel has to travel further than the inside wheel. With a conventional differential this can only be achieved if one wheel skids, which isn't great for handling. With a limited slip diff, within limits, the wheels can rotate at different speeds.

What do I win?

[Ryder35]

thegman said:

Ryder35 said:

Wikipedia

Damn, caught out!

[Ryder35]

OH, and while I am bored at work and trying to increase my post count, does the T350 have a LSD?

[itsallyellow]

grumbledoak said:

When you go around a corner, the outside wheel has to travel further than the inside wheel. With a conventional differential this can only be achieved if one wheel skids, which isn't great for handling. With a limited slip diff, within limits, the wheels can rotate at different speeds.

What do I win?

Very wrong im afraid.....

[grumbledoak]

itsallyellow said:

Very wrong im afraid.....

[thegman]

grumbledoak said:

When you go around a corner, the outside wheel has to travel further than the inside wheel. With a conventional differential this can only be achieved if one wheel skids, which isn't great for handling. With a limited slip diff, within limits, the wheels can rotate at different speeds.

What do I win?

With a normal diff the wheels can rotate at different speeds. That is the point of a differential. it balances the torque between the wheels. Problem occurs when one wheel presents no resistance. At this point it tries to balance the torque by sending all the power to the free wheel. The results in effectively losing all drive - which means your ability to control the car is substantially reduced.

Edited by thegman on Tuesday 30th December 14:22

[grumbledoak]

thegman said:

With a normal diff the wheels can rotate at different speeds. That is the point of a differential. it balances the torque between the wheels. Problem occurs when one wheel presents no resistance. At this point it tries to balance the torque by sending all the power to the free wheel. The results in effectively losing all power - which means your ability to control the car is substantially reduced.

Thanks muchly.

[blueST]

As I understand it, diffs are all about torque distribution. A normal open diff can only deliver an identical amount of torque to both wheels. So, if one wheel can only accept a small amount of torque (maybe due to being on ice), then the other wheel will only receive that same small amount of torque, which may not even be enough to turn the wheel.

[laz11]

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

[thegman]

blueST said:

As I understand it, diffs are all about torque distribution. A normal open diff can only deliver an identical amount of torque to both wheels. So, if one wheel can only accept a small amount of torque (maybe due to being on ice), then the other wheel will only receive that same small amount of torque, which may not even be enough to turn the wheel.

That sounds right. Thanks for the correction.

[thegman]

laz11 said:

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

You will only notice it if you lose traction. At this point you will still get drive from the wheel with traction. I would guess the end result is a more stable car when at the limit of traction.

[Apache]

laz11 said:

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

It'll cancel out torque steer, I had a Saab 9000 fpt and it was a bit of a wayward hooligan, I then tried one with an lsd fitted and I could bury the pedal any time and it simply went where it should

[thegman]

Apache said:

laz11 said:

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

It'll cancel out torque steer, I had a Saab 9000 fpt and it was a bit of a wayward hooligan, I then tried one with an lsd fitted and I could bury the pedal any time and it simply went where it should

What do you mean by torque steer? Are you talking about FWD cars?

[laz11]

thegman said:

laz11 said:

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

You will only notice it if you lose traction. At this point you will still get drive from the wheel with traction. I would guess the end result is a more stable car when at the limit of traction.

And that's only when there is actually anything to grip onto...in bad conditions a LSD presumably is not going to be much help because there just simply isn't enough of a decent surface for the tyres to grip onto

[blueST]

From my extensive experience of ermm..... playing Gran Turismo, I believe thay can promote understeer.

[Apache]

thegman said:

Apache said:

laz11 said:

Thanks chaps! so as far as what I (or any of us with LSDs) would notice, in comparison to the same car without a LSD, is more grip at the rear wheels when cornering?

It'll cancel out torque steer, I had a Saab 9000 fpt and it was a bit of a wayward hooligan, I then tried one with an lsd fitted and I could bury the pedal any time and it simply went where it should

What do you mean by torque steer? Are you talking about FWD cars?

In the example I used yes, for a rwd drive it'll allow you to control a slide much more easily with less likelyhood of it snapping back. Drifters prefer a locked diff but as they tend to use them on the road as well, settle for an lsd

Edited by Apache on Tuesday 30th December 14:47

Edited by Apache on Tuesday 30th December 15:00