Rob S

I'm hoping to get some specific advice from the experienced 944 group regarding the setup of my car. I have a streetable 89 944 S2 (weighs 2900 lb) that is used almost exclusively for DE or lapping days, but it is driven on the street to and from the track, so it has to retain at least some street manners. I have equipped it with 30mm rear torsion bars, 375 lb front springs on adjustable perches, Koni yellow shocks (single adjustable), 968 M030 sway bars front and rear, and 16 x 8 Design 90 wheels, with Toyo RA1s (245/45-16) shaved to 4/32. It retains all its rubber suspension bushings. Ride height at the fender lips is about 25 1/4 in. front and rear.

Questions:

1) Is that ride height okay?

2) I'm particularly interested in knowing the optimum camber settings. I'm tempted to go with about - 2.5 deg. front and -2 deg. rear. Is that appropriate? Is that recommendation the same for all tires (Hoosier, Toyo, Kumho) or does the optimum camber depend on the specific tire?

3) What would be the recommended toe settings front and rear?

4) What would be the best target tire pressure(s) hot? I used to run Hoosiers at 42F and 40R, but I'm guessing the Toyos need to be a bit lower.

Pardon me if these questions have been asked and answered before in this forum. I did a search and found a ton of info -- too much maybe -- but it was often for slightly different cars or different applications. I'd appreciate any help from those who have experience with these matters.

RedlineMan

First off, I'd say the spring rates are a little unbalanced. A 30mm t-bar is good for about 335lbs. Most guys running that much rear spring (330-ish) are doing the same in the front, meaning 600+. I'd be careful until I knew I was up to that task!

Questions:

1) Is that ride height okay?

Just fine. Not too low, not too high. I run about 25.5 because I can still get a jack under it without blocks and such. It's fairly easy on the ball joints too.

2) I'm particularly interested in knowing the optimum camber settings. I'm tempted to go with about - 2.5 deg. front and -2 deg. rear. Is that appropriate? Is that recommendation the same for all tires (Hoosier, Toyo, Kumho) or does the optimum camber depend on the specific tire?

A lot depends on your driving style. Hoosiers can stand a lot of camber, where the others may not "like" as much. -2.5 is not extreme, but tire wear will tell you where they need to be for your style. I run differential camber in front at 2.7/2.4, and 2.2 rear. I get pretty fair tire wear, perhaps a little too much inner with MPSCs or RA1s.

3) What would be the recommended toe settings front and rear?

Honestly, with the aforementioned spring rate potential I see, I would run factory toe settings for a while (5/64ths total toe-in front & rear). Toe is very important at keeping a car stable at speed, and if I had to stick my neck out I think you are going to get some oversteer. Don't need to help it any by making the car twitchy. If you find the car does work with those spring rates, you could try 0 front and maybe just a smidge in the rear for starters. I am running 0 all the way around, and my car is very stable. Could be partly the driver too!

4) What would be the best target tire pressure(s) hot? I used to run Hoosiers at 42F and 40R, but I'm guessing the Toyos need to be a bit lower.

Toyos don't mind being 40 hot at all. Just keep your pressure increase in a comfortable range; about 8lbs.

a4944

I have about the exact same setup on a 1986 944 Turbo except that I have 350 lb springs in front. It handles very well with the 245 Toyo RA1s all around (fuchs on my car). I drive to/from the track with a tire trailer.

I run around -2.9 camber up front and -1.4 in the rear. It was the most I could get. I was shooting for -3.0 up front and -2.0 in the rear. I was wearing the outside of the fronts at my previous setting of -2.2 camber up front. I was having ball joint issues so it has been difficult to judge wear, I have since gone to steel control arms. I think your camber setting would be a good starting point and then go from there. I run 0 toe up front and slight toe in at the rear. I shoot for around 40 hot front and rear. I have not been running Toyos for very long so others may have a better suggestion.

Not sure about the ride height.

Mark

Dave in Chicago

As above... I have found that the RA-1's start to feel a bit greasy just past 42 hot. I have found their sweet spot on my porky (3100 lb.) 968 to be 38-42 psi, often running them right at 41 hot all the way around on my car.

Dave in Chicago

I hit the "go" button too soon. Two more thoughts:

1) I always ran the Koni Yellows at or near full hard on my 944 'NA. YMMV.
2) The camber may make the car "fun" in rain and particularly snow (ask me how I know). You need to pay attention to keep the car straight.

Techno Duck

Redlineman. im curious about your ride height. Do you run at 25.5 with stock ball joints?

I am looking to lower my car a bit..but want to know whats the safest range keeping stock balljoints. I already have it lowered about 1/2 inch. I cant remember exactly what the height to the fender is right now.

I still need to try the rear lowering trick...the stance of my car looks funny with the rear end sticking up.

Z-man

Rob S: I run a bone stock 944S2 on the track - only upgrades I've done is M030 front sway + Welt 22mm rear sway. I would recommend changing your rear sway bar to the Welt unit to get the rear end a bit stiffer. It seems to me that your car probably exhibits a pronounced understeering attitude the way you currently have it setup.

As for tire pressures - I run the Toyo's 245-45/16's at all four. 38-40psi HOT is optimal for that tire. As such, I start around 32 - 33 psi cold.

Nice to hear of another 944S2 out there!
-Z-man.

joseph mitro

redlineman - i'm a little confused about the front spring rate you mentioned. i've always heard a 400lb front spring will balance out 30mm torsion bars in the rear. (ps - i DID finally get that rear toe out taken out of my car! it's got 1/8th total toe in. it feels more stable under hard braking now, and we'll see how it handles on the track this weekend)

Eric_k

For my DE 968, I ran camber at 2.5 front, 2.0 rear, 1/8 total toe-in front and a smidge of toe-in rear. I don't have experience with your spring rates. I ran 450 front, 600 rear on Bilstien coilovers. I got pretty even tire wear at Pacific Raceways with that setup. I run my Toyos at 38 hot.

Good luck,
Eric

macnewma

John, I'm a little confused by this as well.

gman1868

You could do what I did, buy an Intercomp Deluxe Pyrometer and then test at the track.

Make sure you drive hard for 4-5 laps, all the way to pit out. Then pull over right away (don't go all the way back to the paddock) to measure your temps. The inside, center, and outside should be within 10-15 degrees across the tread face and if the camber is out of whack the inside will be the warmest on both sides of the car.

Rob S

All,

Thank you very much for your advice and observations. My car is being corner balanced and aligned at this very moment. Based on the collective responses, it appears that my initial target for camber (-2.5 F/-2.0 R) is pretty close to where I should start. Ride height will be 25 1/4 in. Toe will be near zero front and rear, maybe slight toe-in at the rear. Because John expressed some concern about oversteer, I'm going to start with my rear sway bar in the "softest" setting initially. Tires will be 38 psi hot.

I've been driving this car in autocrosses and on the track for about 5 years now. I've been running it in a very stock configuration (except for the Hoosiers and the 968 front sway bar) -- that means stock torsion bars and a stock rear sway bar. The camber settings were -2.7 F and -1.5 R for years. But my last set of Hoosiers corded on the outboard shoulder in just 8 hours. I figured it's partly because I'm stressing the tires in that region due to body roll, which was pretty extreme. I even found myself leaning like a motorcyclist, as can be seen in the attached photo from last spring at Pacific Raceways, Turn 3A. I didn't realize how much I was leaning - which I'd rather not do. Maybe this will encourage me to sit up straight.

In order to limit the body roll, I opted to go with the torsion bar/spring setup I descrbed above. I drove another S2 on the track that was identically set up, and loved it, so I decided to clone it. I chose to do all the work myself. The front coilover/adjustable ride height kit was no problem, but to change the rear torsion bars is, in the words of a good friend of mine, a "hateful" job. I obviously had adequate opportunity to change to a more rigid bushing for the spring plate (and elsewhere), but opted not to do it for the sake of streetability. I did, however replace the rubber bushings with new ones, which come with spring plates attached to them! They were surprisingly inexpensive, at $140 each (Hendrick Porsche), considering certain bushing sets alone cost more than that. The complete suspension job probably took me about 20 hours, including several hours online at this site and others learning the best way to do it. I have to strongly endorse the following instructions for indexing torsion bars of a different spring rate. This method, which appeals to my engineering sense, involves some simple measurements before disassembly and a spreadsheet that calculates the desired angle change for the spring plate based on the stiffness of the new torsion bar. On the very first try, I nailed my target ride height to within 0.25 in., and I still have the adjustability of the spring plates (+/- about 3/8 in) to dial it in further. No guesswork, no "three attempts" to get it right like I'd been reading.
http://az.pca.org/tech/articles/upgr...orsion_bar.htm

Another interesting observation. I had my Koni yellow single adjustable struts off to install the perches and new springs. I was very interested to find how nonlinear the stiffness adjustment is. About 80% of the stiffness gets dialed in during the last 10% of adjustment. Most of the stiffness comes in during the last 45 degrees of rotation of the adjustment ****. Not what I was expecting.

Erik_K : Thanks for chiming in here too. We met the last time I was at PR. You and your friend were out there with that beautiful 968. See you this Sunday, maybe at the PCA day?

M758

I agree with the others.
I run 30 mm t-bars with 350lbs front springs. Works great and has very similar to stock balance with tad bit more oversteer.

Did you get you motion ratio mix up? 350 front need 600 rear in coil overs to balance as the rear coilover is 56% effective or so.

M758

Thanks... I created that spreadsheet a few years ago when needing to put 28 mm bars in my 84 944. Here is link to the updated version (same with some pics to make it easier still).

http://members.rennlist.com/m758/tbarreindex.htm

Rob S

Oh, M758, Joe, that's you, is it?! I've seen your posts here for a long time (have been lurking and reading just some of your 5614 posts), but I didn't connect you with those instructions. Duh! Thank you very much for doing that work on torsion bar indexing and for publishing it. It's so cool that science really does work, and you saved me (and maybe countless others) many hours of toil and hassle. I made multiple changes in one session by using your algorithm. I went to a stiffer bar, I changed the ride height very slightly downward, all while successfully compensating for centering my spring plates (which had been in the fully lowered position, and I wanted to start over with them centered). And as I said, it worked on the first shot.

A couple of observations. What I found most useful was the total angle change of the spring plate relative to the torsion tube housing. I used a digital inclinometer (a *very* useful tool for this sort of stuff) to verify the desired angular change. Turned out that I was looking for an 8.1 degree change, which just magically happens to be exactly one spline on the outer end of the torsion bar. At the time I was doing this, the torsion tube was on the floor, out of the car. Because it was rocking around, I clamped it in a big vise that I use as a portable clamp. That stabilized the torsion tube so I could get repeatable angle numbers.

Your spreadsheet (and other posts I've read) suggest that 944s come stock with a 23.5 mm rear torsion bar. I measured mine (and I'm glad I did). It turned out to be 24.25 mm. Does that check with reality? I don't know the specs for an 89 944 S2. My impression was that the torsion bars were stock, but maybe they weren't. I'm glad I checked though, because it would have made a significant difference.

Again, thank you very much for publishing that very useful algorithm.

Rob