LSD - essential or a dead weight

[James_G]

All,

I've been doing some reading recently, specifically the Evo test of the new C63 Coupe and Chris Harris says that anybody who considers themselves any kind of driver should spec it with a limited slip diff.

Equally, reading about suspension upgrades to various BMWs that Birds (of Hartge fame) supply, they say that a RWD drive car without an LSD is and I quote "as much use as a one legged man in an arse kicking competion"

Now everybody likes to claim that they are a driving god but on the road I play it safe. I never go exploring the limits, partly due to the traffic, partly because I like my licence and partly because the limits are way high in my car. Of course an LSD means you can drift like a good one, but seriously, who does this on the road? This all means that I rarely ever see the TC light on the dash.

A friend thinks this is because I have an LSD currently so traction is better with it, and I think this is because I am driving below the limits of needing one. I used to track a 944 S2 and I can see how that car could have benefitted from an LSD under those circumstances, but again never on the road.

So, I'm thinking that say I was buying a car where a LSD was an option (new Audi S4 for example) that I wouldn't tick that box as it's uneccessary, unless I want to paint black lines everywhere. Or, and it's a big or, does it actually help the handling below the limits?

Your thoughts please.

 

[pvr]

On one of the Lakes runs, cars without LSD simply could not get up the hill as the turns were so sharp that they would end up having a spinning rear wheel (was wet as well). With the M, I did not have any issues what so ever, so it is not just speed related.

 

[lacroupade]

It is an interesting one and I suspect that its a feature you can 'drive round' a lot of the time.

I can only relate how an LSD works on my 4x4s.....these ones are clutch-based (I think the type you find on a saloon car might be electronically controlled as well, I'm not sure) and in simple terms, if one wheel starts to lose grip (which with an open diff would immediately cause that wheel to end up spinning wildly and take all the drive away from the other wheel in the process) the clutch packs kick in and start to 'firm up' the diff so that the wheel with grip gets more drive and the one thats spinning is slowed down, keeping drive effectively going to both wheels at a controllable rate.

So in normal conditions its behaving like an open diff, but when grip gets difficult, its almost like a solid rear axle.

Its also useful to know that you MUST fill it only with the correct LSD oil.....which actually is less slippery than normal gearbox/diff oil. Using the latter stops the
clutch packs from working effectively as they rely on a degree of friction to operate. But since, as I say, I am not familiar with saloon car variants I don't know how applicable that is.

But theres no question they are effective. Land Rover owners with standard builds hate it when they see an LSD-equipped two-ton 4x4 and only 150bhp, wheelying out of a side road LOL.