Do you really need an LSD?

[James_G]

There's was a for sale post recently where a D5 was being sold with an LSD, a rarely selected option it seems. A comment that followed suggested it was "a must".

Ignoring the specific car for a moment, in normal everyday use (i.e. motorways, dual carriageways, urban environments) is there any benefit to having an LSD? I ask because I've had cars with LSDs and those without and other than a bit of chatter when in reverse (take a bow, MX-5) I absolutely could not tell in normal driving. Or to put it another way, the kind of driving and/or the way I drive means that I never ever lose traction under power, except in really bad/snow type conditions

The only scenario when I wished I'd had an LSD was doing a track day at Lydden Hill and there's a tight 180 and in a FWD car without an LSD I would spin up the unloaded inner wheel. I sold that car and swapped to another FWD car, this time with an LSD, and I could tell on some other track days that in the tighter corners you could get on the power earlier. But I've never got anywhere near to the levels of driving commitment on the road that you can easily achieve on a trackday.

On the road, the most torque I've had regular access to was 620nm in a Mercedes C350 CDi (no LSD) where the rear tyres lasted 20k miles and I never had an issue with traction.

So two questions:

1) Do you generally have to be driving on the aggressive side of "neutral" to benefit from an LSD in normal use.

2) If you are a smooth driver who likes to make progress but who isn't interested in track days is an LSD a waste?

[ScooBeeFive]

I think it depends on the car. I had a 130i about 15 years ago which had an open diff as standard. The rear end setup was so stiff, one of the wheels would always be loosing traction. On uneven sections of road, the traction control light was always flashing, which meant turning it off usually. In tighter corners, it would easily start to lift an inside rear wheel and again traction control would cut in.

After a couple of months I had a Quaife LSD fitted and it transformed the car. You really would not believe the difference - it was night and day.

When I was buying the B5, I was concerned that it had an open diff with all that power. I was fully expecting the same experience and to be making another trip to Birds. However, it's unbelievable how it puts the power down, wet or dry conditions. I think the rear end is so compliant and the damping so good, there is a lot more mechanical grip than with the 130i - it keeps wheels on the ground much better. I also think that tyre technology has moved on a lot in 15 years - the Michelin PS4Ss are incredible.

I'm sure if you were to drive it really aggressively, or wanted to drift around islands etc, you might want an LSD, but for that sort of driving you'd probably look more to an M car anyway which has one as standard.

[Frosty]

My D5 F11 has the factory LSD and it does lay the power down very smoothly. My brother has an F31 D3 same power unit but no LSD, totally different.

[Metrics]

I've done over 60k miles in my D5 and never once felt it needed an LSD. The way it put it grips and puts power down is super impressive.
On the road, with a diesel Alp (mile muncher) I really doubt there's any benefit at all.

[Yad3100]

My m240 was completely different after fitting a genuine plated bmw diff, so it about your driving style and car power that should drive the answer.

[Norrie]

On my B7 100% no. I recently got an M235i, but use as everyday driver, so am uncertain . If I did I would go to Birds I think.