Dave in Chicago

I really like the way my full-race suspension 968 F-stock car drives right now. Quick, comfortable, quite well balanced. But... I do get inside front wheel lift of a couple inches and it is often. Is this just the nature of the 944/968 series chassis in racing? If not, I imagine I need a bit more spring.

Would welcome input from my fellow 944/951/S2/968 racers and trackrats out there.

Thanks in advance,

trackjunky

Dave, I get the same thing with my car. I just went to a stiffer rear spring to see if I can stop this. In pictures, it looks like my car is "falling over" on the outside rear opposite the front tire that is being lifted. Do you see the same?

spazegun2213

My old car did this in a few corners but then again the spring rate was fairly soft. I've not heard about this in the new car, or seen it on track on other 944 cup cars.

Van

In my experience, it's the older 911s that are prone to lifting a wheel. I've never seen evidence of lifting a wheel in my 951 (with 500lb spring in front and 700lb rear).

What sway bars are you running (specifically rear)?

M758

You need stiffer rear springs. There are some spots where I might be able to get a front wheel up just a little, but only barely noticeable.

complexx

700 lb springs in the rear? is that standard among 944's? It seems very stiff. Reason why I ask is that I think we might be too soft back there and have been wondering how much is needed.

Larry Herman

I agree with Joe. You definitely need stiffer rear springs. You are lifting the front wheel because your car is sitting down in the back under acceleration. Match the stiffer springs with either a stiffer front bar, or a softer rear bar to retain your current balance.

Mike Buck

What spring do you have in the back?

I have a 500. T-bar still in there, but indexed out of the way, afaik. Never felt I had an issue with lifting the front tire, but someone did mention it to me at a DE recently. Said he could see me slightly lifting the RF going up around Summit Point T6/7 area. I am only running shaved RA-1s, so I may have to take another look at my suspension after I get my BFG R1s. I run my Tarret front sway full soft, so I could probably get away with a stiffer rear spring and retain similar balance like Larry said.

Van

I am not using the rear torsion bars -- but coil over shocks. The shocks mount to the rear control arm about 2/3s of the way from the pivot point to the center line of the hub.

Because of this, you need to run a higher rate spring than your "intended wheel rate". Running the 500s in front and the 700s in the rear give me about the same "wheel rate" front and rear.

I've been in cars with wheel rates of about 400lbs all around and thought they handled very nicely.... That seems to be a sweet spot for bumpy tracks and occasional road usage.

RICHVIZZ951

Dave
I am chasing the same issue and concur with the others you need a higher rear spring. Do 968's have T bars, if sso you still got em??
I Imagine you a running a fairly heavy car due to your class. 800's in the rear is not at all unheard of.
Only way to find out is to goto the track with a few sets of springs an have someone stand at the corners in question. I would work in 100lb increments, and prob start at 600, but dont know what you presently have.
Good Luck

Larry Herman

My son runs a 951 with coil spring rears (no torsion bars) and has researched all kinds of data on spring rates and packages. Here is a great site on effective spring rates and spring packages. BTW the effective rear spring rate is .65, so if you were running 400 front springs and wanted to match that rate in the back, you would have to run 615 lb rear springs.

RedlineMan

Hmmm...

I have always used .56.

Wheel lift is NOT normal to the 944 as it is in the 911. Spring rate can definitely effect this, but you also need to look at roll stiffness. It is not uncommon for people to have a much larger sway bar on a car than it really needs. Many of the available 944 front bars are indeed larger than the need.

On a softer sprung car, the sways do a larger percentage of the job of leveling the chassis. When it comes to serious track or race cars, it is the springs that really control roll, and the sways are down to tuning balance. Regardless of the application, it is also not uncommon for people to crank these bars up tight thinking they are reducing body roll.

When you get some serious springs, you should start with sways full soft, and then use them to balance the chassis only. Otherwise, you may be running with too much roll stiffness, the end result of which is a loss of suppleness and often grip. If the car feels too floppy with the bars at full soft, adjust your damping (if so equipped). If this does not work, go with stiffer springs.

In my experience, you don't necessarily need that bigger sway bar, especially in the front. If you have the correct spring rates, the bars can be smaller, and again, most of what they are used for is tuning balance. Remember that a sway bar is TRYING to pick a tire up. NOt necessarily what you are looking for, eh?

My car is at 500F/450R full coil with Welts at 2500lbs and change. It would lift the front inside at times, causing brake lock when trailing into some corners. I backed the front bar to full soft and it did mitigate the lift quite a bit.

Not completely, but...

Larry Herman

Yeah, we thought that it was .56 too, but that website showed .65. I guess that we are still not sure, but if you go with .6 to hedge your bets, you won't be too far off. BTW, Dan runs 400 in the front & 550 in the back, and his car comes off of the turns like a rocketship. No mid-corner or exit understeer at all.

smlporsche

Great thread.
I did not know about the multiplier for the rears...

I'm currently running 450's on all 4 corners with MO30 sways and feel the car is pretty well balanced.
I do have some lean in the corners and have been thinking on upgrading to 550's all around but after this discussion maybe I should just increaase the rears.
Thoughts??

Van

Eddie, do you have torsion bars in the rear?

Over the years I've run into people who use a much heavier spring in either the front or the rear, and they've been happy with their cars -- much to my surprise. Being the engineer I am, when I set up my car, I decided on similar wheel rates all around -- and I'm happy with it!

So, there is clearly a buffer of personal prefference here. You might be best to pick up a few pairs of springs with different rates and do some "trial by error". I'd be curious to know how your car feels with 450s on the front and 550s on the rear -- and then do a test with 650s on the rear!