[s-cars] urS Best Suspension?

[Theodore Chen]

--- Bill Mahoney <wmahoney at disk.com> wrote:
> Fellow Racing Engineers-
> Under the a$$umption that I can go and stop fast enough now... and
> perhaps a CRB might be just sitting in Pauls garage waiting for me;  I
> would like to solicit some thoughts on coilovers, lowest possible ride
> height, proper sway bar size and ideas on what would be theee best
> suspension to turn the urS into a go cart?

lowest possible ride height most likely isn't the best ride height for
good handling.  first, you need some suspension travel.  if you run out
of travel, the wheel rate goes way up, and you will lose grip.  i always
laugh at the rice boys who slam their cars into the weed, and bounce over
small bumps.  they think that because the ride is horrible, the car must
handle really well.

second, the UrS4/S6 has strut suspension.  you need to pay attention to
roll centers and camber curves.  if you lower the car too much, you might
find yourself on the part of the camber curve that produces little camber
gain as the suspension compresses.  then you'll find that the car loses
camber overall, as the camber gain from suspension compression isn't enough
to make up for camber lost to body roll.

i don't have any experience with the UrS4/S6, so somebody else will
need to come up with numbers.  i'm just pointing out that lower is not
necessarily better.

> WRT coilovers; are there any preferred brands?  i.e.
> http://www.kwsuspensions.com/
> Is there something that will work for street and then firm up and add
> neg. camber for track?

you'll want adjustable dampers, so you can dial in street and track
settings.  adjustable camber plates would be useful in the same manner.
just mark the street and track positions on the plates, and you can
swap adjustments without having to get the car realigned each time.

> And to fully expose my ignorance, are sway bars suppose to just keep
> wheels square with the road?

"sway bar" isn't a very accurate term.  they are really antiroll bars,
and their function is to resist body roll.  they do this by levering
against the inside wheel/suspension assembly when the outside compresses
more than the inside.  the drawback is that they tend to create some
lift on the inside wheel, which is why you see race-prepped FWD cars
lifting the inside rear wheel off the ground (they run very stiff rear
antiroll bars to try to maximize traction at the front wheels and reduce
understeer).

also, bigger antiroll bars tend to make the suspension less independent,
since you have a bar connecting the two wheels.

-teddy


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