Setting up my car is certainly been a learning experience. Since I run in
Street Mod, it is close to anything goes. Many people can look at what others
are doing, and do about the same on their cars, but I have not run into
anyone else pushing my type of car to the levels I am at.
My car is a 1983 Toyota Celica GT-S with the semi trailing arm (IRS) rear
suspension, and basic struts up front. Most of the books say the camber and
toe curve are pretty bad on this type of suspension and to make it handle it
has to be really stiff to limit motion.
I actually do drive my car on the street, and in fact, it will be driven all
the way to Topeka, and back to Chicago. So I have it stiff, but not rock
hard. The car weighed in at 2677 at the Peru tour. The distribution was 52.5%
front and 51% left with me in the car. This is very good balance for a front
engine rear drive car. I have 325 lb.in front spring which give almost that
as the true wheel rate (the struts are nearly vertical) This gives a firm
ride, while still taking bumps with some composure. I have a bit over 2
inches of compresion left before the bump stops touch. If the corner weight
was doubled, it would just touch. The stops has about 3/4 inch of compression
before it become rock solid. I have only hit it that hard once, it was a bad
pot hole on the outside tire in a hard turn, over 1.2 G's reported by GEEZ.
My rear springs give a wheel rate of about 280 lbs/inch, making the
suspension frequency almost identical to the front. Due to the geometry, I
have a little more rear travel before bump stops, but they do hit harder when
they do hit.
I was running stock sway bars for a long time, with just Energy suspension
urethane mounts and end links. The front bar is 24 mm and the rear is just 19
mm. This setup gave a near neutral steady state balance, with just a tick of
oversteer as the grip was better. I think more body lean caused the rear to
get looser. In transients, the car would get very loose. I dialed this out a
bit with more front shock, but it would still step out unless I was careful.
I decided on more front roll stiffness. I see all the fast S2000's, Miatas,
etc. a;; running very large front bars, and they seem to work very well. I
also have trouble with spinning the inside rear tire, even with the limeted
slip diff, so this seemed like a good idea. I installed a 34 mm hollow front
bar. It also has longer arms, so using the Fred Puhn formula, it should be
about 70% stiffer. To lessen the change, I put rubber end link bushings back
on it. To my suprize, the car was still loose. I then switched back to
urethane end links, and the car was still getting loose. I got to take tire
temps and found something very interesting. My outside front tire (the course
ended with several right turns) was still showing hottest on the outer
shoulder, but it was much closer than before, I run about 2 degrees static
camber. The outside rear tires runs at 2.2 degrees negative and was showing
dead even temps across the tread. The rear was a bit hotter than the front,
and the car was still loose. The inside tires (right side after the end right
turns) both front and rear were quite a bit hotter on the insdie edges. The
rear showing this much worse. I played with tire pressures a bit, and it
started to feel better, but by the end of the event, the car was a total
handful again, but I think the tires went away. I have about 70 runs on this
set of Hoosiers. I just mounted up a new set for Nationals. I was hoping to
scrub them in and heat cycle them this week, but it was raining so hard on my
way up to Milwaukee, I gave up and turned back. Anyone know if the event was
effected?
In any case, here are my questions. My car has very similar weight
distribution to the S2000 and Miata. They seem to run as much front bar as
they can fit. Has anyone had an experience where too much front bar on a rear
drive car really hurt the car? Either too much push, or any other problems?
At the Peru tour, I saw all the S2000's and Miatas with the inside front tire
well off the ground. The pictures of my car in the same turn showed the
inside rear tire half off the ground. This was with the stock bar on the
front. This is what prompted me to go with the big front bar.
My car seemed to get more front grip with the bigger bar, I think this was
due to reduced lean keeping the tire on the ground better. Going by this
assumption, I have now put spherical bearing heim joints on the ends of the
34 mm bar. I will not get a test autocross until Nationals now, Oops!!
Trying to push it as hard as I dare on an empty street, the car feel rock
solid on turn in now. Lean is definately reduced, but the tail can still be
coaxed to step out, but I have to try not, it is no longer loose at all
times. I have range to go both up or down with all four shocks, and I can
somewhat adjust the rear sway bar.
Any ideas what I should expect? What is the worst thing? Too much push? The
car still goes into drop throttle oversteer with ease, and with 300 lb ft of
torque, it will do power on over steer also. This has made it so I can only
use about 1/2 throttle coming out of turns. With a little push I am hoping to
lay down more of my power.
Just in case, I am bringing 2 sets of softer end links as well as the stock
front bar. If the car totally sucks on the first day, I can switch it back
for the second day. I was only .2 seconds out of the trophies on a two day
total at Peru, and that was having to baby it out of the turns to keep from
spinning out.
Oh well, I am really looking forward to flogging my car around Topeka. So far
it looks like I might have the oldest car in SM. With 46 SM cars (not
counting the STX's) There is 12 trophies to shoot for. With a little luck,
maybe I can take one of them home.
Gary Meissner
#42 SM
1983 Toyota Celica turbo beast
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