How does a Quaife affect suspension tuning?

[AntoineJo]

I have a Quaife in my hands that will be installed shortly, and I am about to purchase some/a swaybar(s). In order to make the LSD as efficient as possible, should I be trying to eliminate as much body roll as possible (meaning bigger swaybar(s))? I have never driven a car with a LSD before and I am not too sure how or if my suspension setup should be tuned accordingly...
Presently I have H&R Sports with Bilstein Sports, front stressbar, poly bushings, stock sways, P7000, 1degree neg camber...
Thanks for helping me out!

[Daemon42]

Well, if you read that massive thread about Shine, and dig up the other post
about sway bars from a week or so ago, both talk about motive traction
when exitting a corner.

If you put a really big sway bar up front, it'll keep the car flatter which is
good for preventing major camber changes during cornering, basically
keeping the tire flatter to the ground maximizing lateral traction. However, the
price you pay for having a large front swaybar is that it unweights the inside front
tire during hard cornering, and if you get on the gas hard enough
that tire may simply spin when exitting a corner and you don't accellerate.
That's one reason that Shine gives for using a big rear sway bar, and a small (stock)
or no front sway bar, and using larger linear rate springs up front to control camber.
It allows you to get motive traction down to the inside front tire
even in a sharp, low speed turn, full on the throttle.

Ok.. But there are other ways to keep from losing traction
to the inside front tire. Obviously, a Quaife or Peloquin TBD is the
answer here. If you have a TBD (torque biasing differential) you
can be assured of sending most of your torque to the outside
front tire when the inside front would normally start to spin.
That means that you can run a larger front swaybar and still
get plenty of motive traction, for a moderately powered car.

I say moderately (NA levels of power), because a TBD is not a locking
differential. It is a torque multiplier. It distributes up to roughly
3 times the torque that can be applied to the lowest traction side
to the higher traction side. That means if one side only takes 30 ft-lbs
of engine torque before it would start to slip (unweighted or low traction surface)
then the TBD sends only up to 90 ft-lbs of torque to the other side (assume it's
on dry pavement, and could take whatever you can send to it). The rest still goes
into wheelspin at the inside front. If the low traction side allows only 10 ft-lbs of
torque before slipping (say one tire on ice, the other on pavement), then you only get
30 ft-lbs to the high traction side. What that means is that you probably still can't
go absolutely nuts with the front sway bar without paying attention to your spring rates .
If you had soft springs, and a huge front swaybar, you'd be trying to control the entire
weight of the car with the sway bar and you could end up unweighting the front
inside tire so much during cornering, that even your TBD wouldn't be able to send
enough torque to the outside front tire to be useful. Chances are pretty slim
that that'll happen though unless you've got a supercharger or turbocharger, so I'd say
you can do whatever you like. Then it comes down to normal suspension
turning in terms of feel and lateral traction. Big front sway bars is usually
more understeer.

The only other affect a TBD has on handling is simply the way it feels through
the steering wheel when it's working. If you come into a hairpin turn, downshift
to first, mash on the gas with a TBD in the car, the steering will feel neutral.
Even if both front tires are spinning (as they do on my car when I do that),
the steering still feels neutral. Even sliding toward the outside of the turn
while hard on the gas, the steering will feel neutral. Normally you'd have
heavy understeer, but because the TBD is sending most of its torque to the
outside front tire it affects the steering. As soon as you let off the gas
everything returns to a normal open differential feel, which usually means
understeer. This neutral feeling while on the gas is confidence inspiring.
If you do start to push during the turn, the TBD encourages you to simply
turn the wheel further, and step on the gas. You could do the same with
an open diff, but you'd spin the inside front as soon as you hit the gas
and you'd still be sliding off the road, whereas with a TBD it actually
works.

One side note. With a TBD, you must *drive* out of a sharp
low speed turn when you're hard on the gas because the steering
wheel won't self center until you let off. It generally will only
affect you that way in first gear in a hairpin turn, or U-turn.

ian