Before anyone says "search" - I've been doing it. I'm not sure if I'm using the wrong search terms but I haven't found as much as I thought I would


Anyway, I'm buying the ground control koni coilovers and deleting the TBs. My car is a full weight (even have the spare/pump in the hatch) hopefully mid 300hp 87 951 and I'm 190-200lbs. I want a "trackable" suspension but at this time my car will only be used as a street car (daily driver) but I do like a stiff sporty feel to the car. From what I've searched it seems like ~500/~400 (f/r) springs are used.

Does anyone have any suggestions for me? The car will also be corner balanced and aligned after this, I can't wait to feel the difference..and no longer have my rear suspension squat so much on boost

 

IMO 500f/400r is much too stiff for road use. look around the 250f mark with matching rears.

 

It really depends on what you "ideally" want to use the car for. For a street car, I think the turbo S setup can't be beat.

 

500# springs will not be street friendly. They might be good for a track-only car that is trailered to events, but I wouldn't even want to drive to the track on those. I've got 350# front springs, and they're 'ok' for street use, but probably a bit more than you would want for full-time street use. 300# springs is a pretty common rate, and very streetable IMHO. Once you decide on the fronts you want, you will want to get some rears which match your front rates. You could play with the ratio a bit to give a bit more understeer (more rear spring) / oversteer (less rear spring) depending on which way you go.

 

A streetable setup and a decent track setup are so different....a compromise won't do anything well.
300 pound front springs with matching rears sound about right for a "sporty" street setup. In comparison, I'm running 724 pound front and 865 pound rear springs for a "big track" setup, and AX would require closer to 600# rate.

 

I did a lot of research on this, and settled on duplicating the 968 Turbo RS suspension on my 944 T. I used coil over sleeves on Koni yellows with 250 lb/in front springs and the M030 anti roll bars. I used Koni yellows in the back plus 27 mm torsion bars and the 19mm 3-way adjustable anti roll bar. I had originally installed the 300 lb/in springs, but they are too stiff and made the car understeer badly (but I like my car to be a bit neutral/tail happy). I set this suspension up for Pirelli P Zero Rossos 225f and 245r, but it works fine with Michelin PS2s as well in 225/255 size. It is a bit tough on the street, and on the track it could be firmer, but overall it's a nice compromise.

Randy Pobst drove my car at Mid Ohio and had very nice things to say about the setup: "Well balanced and very predictable at the limit". This was on street tires.

Bear in mind that many people tell you to go to 400+ front spring rates; in the wet, this is a real tough combination, since it makes it difficult to get traction.

 

from someone who has experience with stock, 250, and 400, I would not go above 300 for a sporty feeling daily driver

 

my friend has a civic with 500lb coilovers and it does real good at the track
your butt will be raw if you drive it on the road and it will fall apart
he had it so low the header got a hole in it from rubbing on the road

 

I initially went from stock Turbo S (150-175# front, 25.5mm t-bar 175#) to custom valved Konis with 300# front and 28mm t-bar 254#. The ride quality was absolutely fine with the 300# / 28mm Koni setup, there really was no compromise in street ride quality. It was good on the track, but I wanted more. I am now running Bilstein Escort Cup with 400# front springs and 550# rear springs. I would say the ride quality is decidedly stiff, but not ridiculous on the street. It depends how bad the roads are in your area. On reasonable road surfaces, it's absolutely fine. On very rough roads it's not great. But...on the track it's fantastic.

 

Cool, thanks for the info guys.

Based on what you guys (and the roads I drive on sometimes) say I'm thinking 275-300lb front. I guess I would like a tiny bit of oversteer or at least neutral. What do you suggest for a rear spring? I'll also see what GC suggests

This may be a stupid question, but will tire sizes have any significant effect on the setup? I have 2 sets of wheels, one set of 16s w/ 245s all around and a set of 18s with 225/285 (will probably move down to a 275 next time I have to change all 4 tires)

thanks
mike

 

Go for 300# then. Really, the ride quality is very good. It's like driving a limo compared to most 911's.

If you want neutral to slight oversteer, I'd recommend a 500# rear spring.

If you want to do the calculation:
front effective rate = 0.9 * 300 = 270#
rear effective rate = 0.56 * 500 = 280#
front / rear effective spring ratio = 270 / 280 = 0.96 (< 1 will generally give oversteer, but there are other factors at work)

Alignment settings and tire sizes will most definitely affect balance, as do swaybar sizes and shock damping rates. With a setup like this and wide rear tires you should be quite happy. If you go for less staggered or equal size tires front and rear, you may want to go with a softer rear spring - something like 450# would be good for a normal 225/255 stagger and maybe a 425# rear spring for 245/245 tire sizes.

 

Of course it also depends on how sophisticated the valving is in your shocks. Older tech will show up in lack of compliancy therefore limit how high your springs rates can be on the road.

 

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That's very true. If you're planning to use adjustable yellow Koni's you'll have to go down on spring rate to have acceptable ride quality on the street. I have JIC Cross dampers(they're state of the art) but still, at my spring rate, it's a track only setup.
Tire sizes will have a large affect on balance. 944's of any description handle best with same size tires front/rear. Fit 255's if you can run the nessasary camber (3 degrees or more) in front.
Balance also requires ~150 pounds harder springs in the rear than whatever your chosen front rate.

 

Other way around.

 

Like 95ONE said, it's the other way around.

The softer sprung end of the car will have the grip (given a 50/50 weight ratio and all other things being equal).
So with softer rear springs the rear tires will have the grip and the front tires tend to push (understeer).
If the fronts springs are softer, then the front tires have more grip and the rear likes to come around on you (oversteer).