Dingdongler

I have a rough idea what a lsd is and know that my current car has one.
However I have no idea whether I've ever needed/used it.

Is a lsd actually useful on a powerful rwd car which will never go on track?

The reason I ask is that a nearly new e63 amg is on my shortlist of new cars. It doesn't come std with lsd, it is an option. Many people who have specced it have done so as part of a 'sport package', this includes suspension upgrades that some say spoil the ride.

Thanks

J4CKO

iTrader: (1)

Depends how you drive, most of the time no, when pressing on they can make all the difference, makes the car more "driftable" but they are expensive hence why very rarely standard and nowadays the manufacturers tend to simulate ones operation via software modulating the brakes. They also avoid that embarassing start where all your power dissapears through the drivers side tyre or whatever is most unloaded, I remember driving our T5 at first and booting it, thinking I had a slipping clutch, it wasnt, I was turning slightly left up a bit of a rise and the slip was the inside front wheel spinning leaving a nice cloud of smoke, an LSD would have locked and split the drive evenly and fired me off up the road or potentially if there is still too much power span both and spat me into the middle of the road.

Sometimes there is a downside, usually on more competition oriented ones where they can cause tranlining, understeer and other undeseriable traits, but usully anything road spec is less agressive and more suitable, racing drivers can drive round the action of a proper track LSD and be quicker, for me I suspect it would just make it worse !

ALi-B

iTrader: (1)

Depends, but.....

You will find nearly all rwd cars have a form of LSD, often unknowing to the drivers who buy them. In the way of active braking on the spinning wheel via the traction control system. Sometimes called "virtual LSD" or elctronic LSD. You will likely find this is what the Merc has as standard (seeing they pioneered alot of the stability/ABS technology behind it).

Some cars with no mechanical LSD that allows the traction control to be turned off (MY03 e39 530 BMW with full DSC for example), will still have the system active to control excess wheelspin, where the rear brakes will apply on the free spinning wheel, but without restricting the throttle. So both wheels spin up and you can do lairy stuff like pretending to be a driving god. Late model Land Rovers also use this to replace conventional diff locks (with mixed verdicts on its effectivness).

On cars that have this facility it works very well on the road; allows a little inside wheel spin first before engaging the brakes on the spinning wheel, giving the driver warning of low traction (wet/greasy road), and not giving the fish-tail-backwards-thru-hedge twitchyness that an agressive mechnical LSD will give on greasy roads. On the downside, when the car is driven hard (eg: track days), it overheats the rear brakes and the system may not repond as quick as a hard driver would like it to (who will often make note of the inside wheel spinning up when hoofing it out of a tight bend).

Mechincal LSDs come in many flavours. Some sloppy, some very agressive. The latter is a handful on a greasy road and will catch out the uninitiated. The prior is much more livable in the real world that is the UK's wet roads, but does allow alot of wheel slip when driving hard (eg; Jag XJ-S; Has a very mild mechanical LSD, as such it will spin up one wheel fairly easily, but still makes good progress, in reality its not more effective than an electronic virtual LSD).

So, IMO. An LSD of sort is required on a rwd. But it doen't need to be a pure mechnical LSD, nor does it need to be an agressive one. Its handy for day to day driving, like pulling out of a junction quickly, or if it snows. Last winter I had to drive an S-type Jag, which has no form of electronic or mechnical LSD, and it consequentally got stuck when it tried to sniff a hill (I did manage to get it moving again with gentle use of the handbrake to stop the spinning wheel and send power to the other wheel which had a little more traction - just like what a virtual LSD would do).

Trout

iTrader: (1)

An E63 really needs to have an LSD. Pulling out of a junction on a greasy road will have your inside rear smokin' like a good 'un without it.

Dingdongler

Thanks.

I had a MB C180K as a hire care on holiday. As I pulled out of a petrol station (bone dry road, temp 33 degs cels!) one/some of the tyres spun and I was a bit shocked. I was not driving like a loon at all as I had my two small kids in the car etc.

I even got out to check the tyres to make sure they weren't bald. Is what happened due to a lack of lsd?

riiidaa

iTrader: (2)

where were you on holiday, road surface makes a difference. In the States it's very easy to spin the wheels.

Dingdongler

Yes, Turkey. It was a proper road though, not an unmade one/dirt track

ALi-B

iTrader: (1)

If you were in a dusty climate, the road will be slippery even when dry. Also if the the tyres have aged a bit, the rubber can go very hard. Pirellis are reputed to be quite bad for this for a "known" brand.

rickya

iTrader: (18)

We'v got one in the family & they are a load of sh&te to drive & always do this, infact its almost impossible to go for a drive in it without spinning up the wheels at some point! And dont get me started on the brakes & build quality. Off topic, these A class/C class coupes etc are not really "Mercedes Benz" & really ruin the brand IMO.

Dingdongler

Thanks Ali

Rickya, must say I was quite shocked. This was afaik the current shape C class (which I think looks really nice), it was nice inside but the drive was awful. Ride quality was fine but the steering was just so vague and the suspension so slow in reacting that I never had any confidence to press on in that thing.

Don't get me wrong, being in a foreign country with my wife and two kids in the car I had no intention of driving hard. But this thing just inspired no confidence at all, I thought MB had made their more recent cars fun to drive??