Bob, my experience was not too scientific (more like trial and error) but
I'll be happy to share my conclusions. My TR-4A SCCA race car was about 2"
from the bottom of the frame to the pavement in front, and about 2 1/2
inches in the rear. I did not use bump stops, and did not have a problem
with shocks or coil bind. I started with the factory competition springs
in front, and shortened them even further (which, of course stiffened the
spring even more). I used Koni shocks, and don't think I ever wore out a
shock. With the stiff front springs and a 1 1/8" front sway bar, I don't
think it would be possible to get to coil bind.
In the rear I used factory competition springs, but did not alter the
spring height. I played around with various mounting brackets for the rear
trailing arms to get the correct ride height and suspension geometry. I
believe there were 3 different brackets used between the TR-4A and TR-6.
Each of these can be used as an inner or outer bracket, and can be mounted
with the notches up or notches down. This gives you quite a few options
for adjustment. To get the car balanced, I had to use a much smaller sway
bar in the rear. I believe I ended up with a 3/4 inch bar (or perhaps even
smaller?) The car seemed to work best with the front end pretty stiff but
the rear fairly soft.
How you set your car up will depend somewhat on your driving style. I know
people who set their cars up stiffer in the rear suspension than I did, but
my setup seemed to fit my driving style, and the car handled very neutral.
It always seemed to do best on high speed courses like Road Atlanta and
Road America. Good luck.
-----Original Message-----
From: Bob Lang [SMTP:LANG@isis.mit.edu]
Sent: Tuesday, February 29, 2000 10:18 AM
To: fot@autox.team.net
Subject: Simple Question: Bump Stops
Hi,
I'm preparing for another phase of "lowering", and I've become perplexed
with the issue of bump stops on the front suspension of my TR6.
The short version of the question is: are the bumps stops built into the
shocks??
I can see that the lower limit of travel is the little "thingie" that
attached to the lower trunnion that also acts as a steering limiter...
but that's not a bump stop per se because it's made out of a hard
substance - sort of the antithesis of normal rubber bump stops. But there
seems to be no upper limit other than the shock bottoming out (topping
out???) or the spring fully compressing.
I presume that in extreme suspension travel that changes the spring rate
from 400-something lb. / inch spring rate to "infinite" instantaniously
would possibly be described as "sub-optimal", at least in regards to
driveability.
At any rate, I don't want to lower the spring so far that I do wind up
binding the shock - after all, I can't buy any new Spax shocks, if
popular rumor about the state of Spax is actually true. And yes, I know
that Carerra makes a better shock - but that's "down the road", to borrow
a euphamism.
So amici, what's the drift on front bump stops on TR4A'a and TR6's??
With regard to the rear bump stops - the lower one is no problem. The
upper bump stop is a bit more problematic - if you lower the car more
than 2.5 inches, you run out of upper bump distance. I can see that two
choices are available - hack out the bump-stop perch on on the body or
modify the trailing arm by hacking down the little tower that the upper
bump stop screws into. I presume that hacking out perch on the body is
preferable, but my question is: do I need to worry (more) about the axle
sliding spline binding (bottoming) as I get the car lower?
Just curious. Any replies are appreciated.
rml
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