por944s2

Why do you need more rubber? Are u running huge hp or a V8? More rubber can slow the car down. What is the car used for? Any sanctioned races or just DE? 944's turn in great but getting the rear to stick is the big issue IMHO. The turbo cup and firehawk cars ran 205 and when thy ran 225 (upfront) were slower.

docwyte

You can try going to an adjustable set of swaybars, but I agree, with the spring rates you're running, you need much less stagger on the tire size...

Dwane

If he were to keep the rest of the setup the same, for simplicity, it would be easier to change rear springs.
What springs would you suggest in the rear? 900#?

lee101315

You usually pick your wheel and tire setup before spring rates.

Assuming this was mostly a street setup on aggressive summer tires, I'd lower the front springs to 350lbs, and add 968 m030 front and rear sway bars if I didn't think it was stiff enough.

Especially since his car is under 2700lbs.

Running the car at autoX events or DEs on slicks would require stiffer rates.

Dougs951S

I'll try to respond to everyone at once. Yes, the 7.5F 10R stagger is WAY too much for the car, hence my desire for a square setup. The car wont be used in sanctioned events for some time, its just a pretty fast DE/AutoX car/hoon machine. Right now its making ~380/400 at the wheels, but I'll be putting on a bigger turbo soon and I have a 16v 3.0 liter stroker motor on my engine stand that I expect to make 500/500. Reducing the spring rates is, in my very humble opinion, neither a good solution nor what I actually want to do with the car. To me, the car feels like it lacks front grip much more so than rear and I want it to handle neutrally while having as much rubber as is physically possible up front (and rear too). I am totally willing to increase spring rates and get thicker sways, but I'd like to avoid softening the car up at all as it already feels too soft to me. The car runs on soft (~180-200 tread wear) summer tires but not slicks. The front motion ratio is .9 so I've basically got 450# effective in the front, and the rear motion ratio of .56 gives me 420# rear effective. What spring rates should I be looking at in the rear to get the car to turn in a little tighter with both my current stagger and with 10x18 all around? For simplicity sake I'm limited to 1000# rate in the rear. Right now it'd be easy for me to throw in some 850#'s.

lee101315

If you're tracking and autoXing, spring rates will be different.

If you search, I remember seeing quite a few track setups which will give you a fairly close starting point.

I've been autoXing a Boxster with a 996 engine for 3 years with 17X9s on all four corners on 275mm slicks, with 550F and 650R springs ( the rear is macpherson). I also upgraded the sway bars.

I ended up disconnecting the rear sway bar to get faster, and many others who track their 986s note that their lap times got faster with slightly lower spring rates. Just because it feels stiffer doesn't make it faster. Anyway, just try a well known setup to get a good baseline, race it, and adjust it from there.

mel_t_vin

From what I recall, that doesn't quite sound correct.

Could be wrong, but I thought R[front wheel] = 0.92 * R[front spring]. In this case, that only turns out to be 10 lb/in, 460 lb/in versus your calculated 450 lb/in.

But I recall R[rear wheel] = 0.65^2 * R[rear spring], + R[torsion], if any. So, in your case, if these numbers are correct, that turns out to be a 100+ lb/in difference in the wrong direction, as you would only be running an effective 315 lb/in versus your calculated 420 lb/in.

Summary: 460 lb/in [front] and 315 lb/in [rear] = recipe for understeer. And, this would echo what Lee had already pointed out.

DER951

I may have missed it somewhere in this thread, but if you're running wide sticky tires on '86 951 spindles, it could end badly, as you have the same wheel bearings as a 356.

I learned this the hard way.

You should upgrade to '87 or later spindles, that will require camber plates to get proper camber back, but sounds like you're headed that way already.

Dougs951S

This is a good point to bring up, im wanting to switch to late hubs and spindles and run lexus monoblocs up front.

mikey_audiogeek

+1 on this. Also, don't forget to play around with ride height as a tuning tool. It affects roll centre height which affects weight transfer; at least as much as sway bars or spring rates in my experience.
Hope this helps,
Mike