heavy fuel

OK so i just finished the first auto-x on the new suspension setup. the car is an 87 944 with 250# Welt front springs, 26mm rear torsion bar, Koni yellows adjusted to about halfway between stops, 26.8mm front, 18mm rear swaybars with stock bushings everywhere. Good 4 wheel alignment with 1 deg negative camber all around. Car feels pretty good, less body roll than before. But the back end breaks loose way too early, can't put power on cause that just makes it worse.

Any of you autocrossers have any ideas?

andy

nh7cy

suspension too tight on the rear end?

Techno Duck

Tire pressures? How much weight do you, if any have stripped out of the rear? Thats a big problem with taking weight out a 944. I would say more than 80% of the major weight you can take out comes from the rear of the car. Might want to increase dampening (stiffen) the front Koni's.

Try doing a mock skid pad test in a nice big open lot (do it safely of course). You can play around with the tire pressures and dampening until you can get the car balanced the way you like. Turn the wheel maybe half or 3/4 of a turn and just keep going in circles and slowly keep accelerating.

The way i setup my car was to set the dampening in the front to get the car into sort of a 4-wheel drift with throttle oversteer on demand. I then adjust the tire pressures accordingly for each specific course. I find the less i make adjustments to on auto-x day, the better i do.

xsboost90

when i go to the autox- everyone takes their spare, carpet etc out of the rear of the car. I leave it all in there. Keeps the weight over the rear wheels better.

heavy fuel

Tire pressures started at 35 fr and 39 rear. do i have that backwards?

this weekend i'll find an ad hoc skidpad - good idea.

thanx,
andy

N_Halbert

There are a number of things that you can do to change this condition. It is a matter of just knowing what change will have what effect and only changing one parameter at a time. The following link is to a table over at Paragon on
Suspension Tuning - the VERY basics It is a good reference to keep at hand when at an autoX or DE.

Your pressures don't seem odd. They would tend to make the car push. Tire pressures should be considered a fine tuning item.

Those were the cold pressures, what were the Hot pressures. I would keep the stager the same but done let it go above 39 on the rear.

You said you had a four wheel alignment done. Did they dial in any toe at the rear? Zero or plus toe will make the back unstable. That would be difficult to tune out with the other settings.

I would suggest starting with the shocks and stiffen up the front then soften the rear if necessary. If this is not enough you could consider putting in the stock rear swaybar.

V2Rocket

Is such high tire pressure normal in autoX? I run the rears on my car at 30-32....

944CS

N_Halbert, you are mixed up. His pressures are aiding in his oversteer problem. The higher rear pressure reduces rear end grip.
Heavy fuel, you should not have a terminal oversteer problem with your current set up. Dial back the rear pressure, start it equal with the front, and go from there. What tires are you running?

xsboost90

with street tires i would put the tire pressures at 35psi front and rear - do a run, check them and adjust from there according to how the car feels- less pressure = more grip.

J Silverman

To a point yes. Tire grip is very much like a bell curve, where you have a certain pressure that grips the most and anything higher and lower will give up some grip.

Since these cars are so close to 50/50 weight balance Id keep the pressure equal front to rear and see what that does to help. Id start somewhere around 38 psi and adjust them based on how far the tires roll over.

tifosiman

Brand of Tires?
Size?
Equal size front and rear or staggered?
What were the pressures once they heated up?

xsboost90

i knew i would get that- yeah i meant to say - under inflated- more grip- over inflated less grip. My RA1s run best at 40psi hot, ive seen hoosiers that run almost 50psi- but that is based on the tire...

pkt1213

I had 15" BBS wheels and ran a 215/60 Bridgestone G009 and I found 39-40 psi front and rear was a good combo.

The previous set of tires were god knows how old and super hard. My *** end was all over in autocross and I would even get the back end to step out shifting into second down entrance ramps.

Mongo

Okay, first of all:

Why spend so much money on upgrades that affect your car's handling without even knowing what you want to be changed to suit your comfort level of driving?

This is the NUMBER 1 mistake of anyone attempting to upgrade their car properly to improve handling. Drive the car first before bolting everything on.

As far as tire pressures go, start at 36 all the way around. If you have 15" wheels with 215/60/R15 tires, you may end up running the pressures up to where you started.

Go EASY on the throttle so you can get a feel on the car. Don't go mashing down on it after braking for a turn. Be progressive with it. Heck in the end, it may not be the cars suspension to blame, but how you drive it.

Soften your shocks on the back and see how the car feels next.

knfeparty

Seriously consider leaving the spare in the back. One of the best times my car ever autox'd on street tires was when I had almost a full tank of gas, when I usually run just 1/4. It's so easy to try one run with it and another without, so why not give it a shot?