That is why I like adjustable sway bars. easy to move a setting and try it out. If it does not work you can go back. 1lbs of airpressure works, but I have always found it hard to get exactly 1 lbs of change hot. usally if I can be with in a 0.5 to 1 psi of my target hot I am good enough. I rarely have the option of taking pressures in hot pit. Mostly it in the paddock after a cool down lap.

 

Another thing to consider, is wether you are running a limited slip diff. If you are, then you can crank up a rear swaybar to compensate for the lesser rear spring rate without worring too much about lifting the inside rear wheel. I can tell you that an M030 F/R setup will not have enough adjustability to get the rear as stiff as you need. You need a Weltmeister, Tarret, or similar bar to get enough rear roll stiffness. When I ran a staggered setup with 350/30mm springs, and a Turbo front bar, I had to put my rear Weltmeister on full stiff. This caused significant wheelspin in my open diff car, but was still fastest (at Mid-Ohio). Now that I have Tarret bars and an LSD, I run 400lb front springs and achieve good balance (with a square setup).

Caveat: This is with a 136 RWHP, 2,600 lb (race weight) 944 NA

 

Hi Jeff,

As a reference, on my 89 S2, which weighs 2900 without me, I have 16 x 8s all around on shaved 245/45 RA-1s that I run at 36 psi hot; 30 mm rear T-bars, 375 lb front springs, 968 M030 bars front and rear, an LSD, Koni single adjustables set full stiff, and about 2.8 deg neg camber in front. Car feels pretty neutral...

CU on the 27th?

Rob

 

ah..good point. The car does have LSD in reasonable heath with stock breakaway.

You folks are a wealth of knowledge - thanks!

Maybe here's the first (cheap) series of steps.

- add a stiffer, adjustable rear bar (have the 3 way adjustable 968 bar on the way)
- consider adding a little more toe out to front
- try a bit little less rear air pressure
- tinker with shock rebound settings (more in the rear, less in the front?)

Next steps after that might be:

- get on a square setup with more rubber in the front.

What's not clear is if I should add more front bar. In general, I could use overall the roll stiffness but it sounds like I may need a rear bar that's larger than the planned 19mm upgrade to maintain the needed bias? Still leaning towards adding the 30mm front bar as well.

 

I might even suggest to the OP that adding MORE spring will help dial out the push. 400 is "soft" and you've gotta be at an optimal point before you can be assured that reducing/increasing spring rate will have the effect that all of the tuning books say it will. You may need MORE spring rate to control roll and keep the tire happy. If less spring rate was always the answer to increasing grip, we'd all be running 50 pound spring rates.

Do the 951's use Mac struts up front? If so, raising the front ride height to help put the front suspension in a better portion of the camber curve may be the answer. If it's anything like BMW's, you also actually increase roll tendency by lowering the front suspension (due to relationship between roll center and center of gravity...yes, it's true no matter what you've read about lower always being better), so without going to a much higher spring rate to help control the additional roll, raising the ride height up may actually help the front to roll over less, keeping the tire happier at it's current alignment setting.

 

Hey Rob....yeah, I'll be there on the 27th as well as this weekend. You doing the ground school on the 13th?

 

Yes they do & yes it is.

 

Brian...working to digest that one. Camber curve is a new term / concept. Sounds like there is some geometry at play here - any chance for a quick concept summary? Sounds like something I need to read up on a bit.

Car is currently lowered about 1" and has about 1/4" fore to aft rake.

Would adding front bar get me to the same place as upping the spring rate?

 

Jeez, I started with 750 fronts and 900 rears and just jumped up to 850 and 1000. Now that......is stiff.

Spend the money on the adjustable sways and have a friend help you monitor tire pressures when hot and TAKE NOTES. Write your car specs down before you start making setup changes! If you monitor your pressures before and during sessions you will answer some of your own questions and thats where you need to go. Write down your assessment regarding handling as soon as you get out of the car. There is no substitue for spending time at the track developing your car's handling. Invest in a few instruments and take the time to gather track temperature, air temp and tire temps.

Never just rely on second hand informaton, listen, digest, test, then record. If you don't record you will never be able to chart your progress accurately. Car development requires paperwork.

Just my two cents.

 

If you're dealing with a pushy car, you should be bumping the rear pressures UP.

Go in 2lb increments. A typical "track day" driver, in typical production chassis, won't feel 1lb. change.

Anecdotal info from the paddock is worth exactly what you pay for it. There will always be a statisticly significant population of idiots & BSers (or both), and it's difficult to detect "Bozo-factor". Beware.

Test stuff yourself. Swaybar adjustments, tire pressures, shock diddles...easy to do...you should be doing them all (one at a time), even if you think you like the handling of your car. Find out how all that stuff affects handling. You might find out that what you think you like is really a wallowing pig. You need to discover it's a pig BEFORE you start buying it lipstick.

 

In my experience, you cannot feel too much of a difference unless you change rates by 50 pounds at minimum. This has been my experience with a 1950 pound 911 and a 2900 pound 951.

With respect to going further on set up...

Is it a street car or an AX car or a DE/track car or a race car? Or some type of combo? Also good set-up is somewhat track dependent. Different areas of the country with different types of tracks require different types of set ups.

I cannot say that 400 pound springs are soft. Depends on what you compare to.

I started in a 944 in 1987, then moved to a family of 951 cars through the 90's. I got lot of set-up advice from professionals, like the guys at Kelly Moss and from Jon Milledge. A bunch of others as well. When I was running my 95, it wasn't too long after the family of cars was raced professionally so there was a lot of fresh info around from people trying to get max performance in pro ranks.

In my cars, I always started out with the Jim Pasha "plus one" concept on sway bars, so at one point I had the 968 M030 set up, including the rear shocks with helper springs. Later I upgraded from there. I'd also move to equal tires in all four corners right at the beginning. I'd also lower the rear and use some ride height specs I got from Jeff Stone at KMR from his experience in Firehawk.

I ran Koni shocks in front... first from a Turbo S, then later some double-adjustables (from Firehawk or Escort) purchased for $30 at a swap meet. There are many more choices these days.

I was an early-adopter on things like camber plates (from KMR) and rear pro Koni coilovers (from Jason Burkette) instead of torsion bars. Eventually I had a 968 transmission and a custom Milledge rear sway bar. A Weightmeister front sway bar, and I ran Fikse 17's with 275's in all four corners. I also ran a bunch of of Karl Poetl's parts as well as having the very first set of production Charlie Arms (bought from Jon Milledge). And I built my own engine, which Jim described in Excellence. 360 bhp at the crank at 16 psi... lots of stuff and advice from Milledge.

Here are some things to think about from the "old school."

Buy a copy of the Puhn Book.

Talk to pros. If there are some in your area, that is great. In terms of businesses, I think Karl Poetl is a great resource

Equal size tires in all four corners.

Plus one sway bars, so 968 M030 front and rear. Potentially experiment with rear first since you have described a desire to reduce push.

Make sure your Koni's are always in good shape. My wife and I did about 6-7 AX's per year and about the same number of track events per year in our 951, at all times running the car pretty hard. We needed to rebuild our Koni's every other year, so we rotated through two sets.

Not related to set up but... if you are driving the car on the track, strongly consider getting some proper control arms. Back in the day I busted two factory aluminum arms... one in AX and one on the track. The track failure could have destroyed the car and people could have been hurt. The PAG motorsports arms were a little better than street car parts, but still could fail. On an early car, you can have factory steel arms welded up. For later cars, I liked the Fabcar parts (make sure you get authentic Fabcar pins... ask me how I know). I also liked the Charlie arms, but I am not sure you can buy these any more. I was never personally too impressed with anyone else's arms or ball joint rebuilding/replacement processes. Things may be better now. PMNA gave advice on control arms in Pano back in 1995 in one month's technical Q&A's as the problems were so widespread. They basically said to run no sway bars stiffer than M030.

Make sure you know the condition of your spindles and hubs. Early-offset spindles were failing in the 90's, so I am sure original parts are vulnerable today. back then a lot of folks changed to later-style spindles.

 

Oh, and if a track car and you are running cast alu factory wheels... think about going to something forged as you look for replacement or additional wheels.

The cast ones crack... I saw this in the 90's so I am sure it still happens now. I know several people with multiple sets of Turbo S forged wheels in 8 and 9 inch widths... these things are still around and come up for sale from time to time. These were the best wheels Porsche ever made.... I bought my first set of 9's from Kevin Buckler back when TRG was run out of his garage.

If you drive on the track a lot, this can be pretty important.

 

^^^ Lots of good information there ^^^

 

Thanks Mahler. Great points...have most of them on my radar screen. The Koni fatigue is definately something hadn't thought about.

I'm aware of the control arms...i'll do some checking into how to inspect the spindles as I do have the early offset variety. Have Fred's book...maybe I should go open it up again.

 

Jeff, having dealt with a similar handling issue in my PCA racecar, I'd heed Larry's initial advise of at least -3.0 camber up front. Anything less and I found the car would push and run high outside edge tire temps. Start there, then work on spring rates. (as in NEW changes)

I spent quite a bit of $$$$ on different springs to find out that front camber is very important on these cars.

Or, option #2, sell it and buy a 996?