At 08:26 24.05.99 +0800, you wrote:
>snip<
>
>Car is unlightened but has battery in the boot
>
>Power at present approx 135-140bhp at the wheels (15.9sec 1/4 mile)
>
>Any suggestions on spring rates and sway bars would be appreciated
>
>Thanks Andy Thompson
Well, in order to say what creates that understeer, you should find out
when exactly that understeer appears. Does it appear during turn-in?
Mid-corner? Exit? The question on when the understeer appears can tell you
a lot of where the understeer comes from. If it appears during mid-corner
(this is the most common with our big triumphs I think), it can be either
1) Too stiff front anti roll bar, or too soft rear anti roll bar, or
combination,
but since I take it that you have no damping of the ARB, and certainly not
adjustable damping, it might be:
2) Too stiff front springs/too soft rear springs, or combination.
Soft springs (within limits) give better grip, and stiffer ones give less
grip. Well, your rear tires have high loads because you're accelerating,
and the weight transfer of the big triumph is substantial, your rear tires
might handle stiffer springs, but I would say you could use softer front
springs. That is if your ARB is effective, softer springs will make the car
roll and pitch more.
If the car understeers during exit and turn-in, the problem probably
resides in the damping. You have adjustable dampers, so you have plenty of
room for experimentation. You could try to soften the front ones a notch or
three, or perhaps better, stiffening the rear ones.
And one last thing. If you're having understeer during acceleration, your
front camber might be wrong. When you go hard on the throttle, the car
pitches backward, and the front goes from -1 deg to +3 or +4. That positive
camber changes the contact patch, and could give understeer I think. I'd
say that -3 deg front would be better. The camber will increase (perhaps to
-4 or -5) when you brake or turn, but that is ok, you have plenty of load
on the tyre at that time, and in the turns you might need -5 to keep the
tyre perpendicular to the ground.
OK, that was my tuppence worth, setting up a "normal" car (if you can call
our triumphs normal cars) can be very difficult in comparison to setting up
a race car, but I hope you got a few ideas from my suggestions. Ultimately,
the method needed is "trial and failure"... And remember, when you do
something to your car that should create more oversteer (or less understeer
in your case), you should drive the car a lot before condemning/or going on
with the idea, your car will react differently, and potentially you will
experience some fast transitions that you didn't have before. And the point
is to get to know the transitions from the right side of line of security...
---Asgeir---
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