knfeparty

so my car has a LOT of drama when you get on and off the gas, even if you're trying to be really smooth

The ride height is fine and it's been aligned by a great shop

stock t bars and stock front springs

I'm about to install 968 m030 struts in the front

I know springs can sag-> decreases ride height but not spring rate
what about tbars?

My plan was to use eccentrics to drop the back end and the m030 perches to drop the front as much as reasonably possible.

But I don't want the nose pointing to the sky and the swaybar brackets kissing the pavement every time I get on and off the gas!

has new koni sports

V2Rocket

bigger t-bar

knfeparty

okay let me rephrase that

is there any stock-legal way to help out? Are the tbars linear, or will indexing them for higher ride height and then adjusting ride height back down with the eccentrics increase the tbar rate for the first part of motion?

jpk

Tbar rates are pretty linear, so indexing them won't change the spring rate any. Unless you increase the spring rate, the only thing that lowering the car will do is reduce your suspension travel and lower the CG just a bit. If you really want to improve the handling, you'll need to install stiffer springs.

On my early car, I started with 250# Weltmiester springs up front that lowered the car about 1.5". Initally, I left the stock tbars in back, and just indexed the spring plates to level the car. The ride was horrible at that point, the front was nice and firm, but the rear would bounce quite a bit on bumps. Even with Koni yellows all around, the ride was brutal on anything except a perfectly smooth road.

After a couple of years like that, I swapped in 28mm bars in back. That was perfect.

If you're doing the struts anyway, you might as well bite the bullet and go with bigger springs as well.

Lousailor

Another vote for stiffer springs and bars. Changing shocks and struts, only dampens motion, but will not reduce it.

944CS

keep a nice rake so that your rear end is helping to turn the car

knfeparty

again, I CAN'T install stiffer springs or stiffer tbars. This is a stock-class car!
CSP=bad. The car will never be competitive in CSP.

So I'm guessing the answer is that without changing the stock tbars and stock springs (the 968 ones are a bit stiffer? 28N/mm) I am stuck with soup ride.

Spidey944

in all of my 4WD vehicles, whenever you adjust the torsion bars up, you also changed the stiffness. Why would the 944 be different if you dont mind me asking? Never owned a car with REAR tbars B4.

J Silverman

Front to rear weight transfer (which is the cause of the nose diving under braking and rising on acceleration) is proportional to the ratio of center of gravity to vehicle wheelbase. So, if you have the formula: W= (CoG)/Wb where W= total weight transfer, CoG = height of CoG, and Wb = wheelbase you can see that as the CoG goes down, W goes down. So yes, lowering the car will reduce the total weight transfer which will equate to less rising/squatting of the front end. First set the front ride height, then use the eccentric to lower the rear. Try to keep the car level at the rockers front to rear. If you cant get the back low enough, then you will have to reindex the t-bars. If youre going to reindex, you might as well put in a pair of 25.5mm (I think) bars if you dont already have them.

V2Rocket

Going somewhat OT here but...J Silverman, with that little equation in mind, would running a stiffer rear end combat the weight transfer dipping? The weight transfered being the same but with, say a 250# rear end compared to the ~120 stock wouldn't there be less motion?

944CS

do not make the car level front to rear, it will not rotate as well - set the rear ride height higher than the front, this allows the wheelbase to elongate as the rear suspension compresses

J Silverman

Stiffer springs wont reduce weight transfer but they will reduce the amount of body motion due to weight transfer, so yes stiffer springs will help to reduce nose dive under braking and lifting under acceleration.

Oddjob

By changing stiffness, are you refering to spring rate?

The function of torsion bars will not be any different in a 944 vs a 911 vs any other car that I know of. Torsion bars have basically a linear spring rate. Changing the index or preload on them really only changes the ride height of the vehicle, it doesnt change the effective spring rate. Same effect as moving an adjustable spring perch up and down for a coil spring - no change of spring rate.

You have to change the diameter or the length of a torsion bar, or the distance between the pivot points (wheel hub to t-bar axis) to change the effective spring rate of a t-bar.

M758

The only way to make the car stiffer is to change the spings or lower the weight of the car.

Autocrossing in stock class means you can't do either. So you are left with alignment and ride height. Rake does play a critical role in balance as does rear toe settings. Just because you had shop align it does not mean they used the right settings for you. Most guys don't run around hard on a stock suspension so the standard "track aligment" may not work for you.

knfeparty

So more rake is going to cause more rotation, and less (static) rear toe in will also cause more rotation, right?

How do these affect the car for corner entry vs corner exit?

This is all great info guys; thanks a lot.