Has anyone come up with these yet? Not looking to replace yet, just accumulating data on the setup.

TIA /bob

 

Excellence quoted Harmut Kristen: "If you take a case of zero as the stock Carrera 2 and 100 as a full-blown GT3RS race car, then the street GT3 should be around 25 and a Supercup racer about 66."

Assuming the Carrera 2 is about 200lb/in and the GT3RS 1800lb/in, then the GT3 would be 600lbs/in. Given the feel of the car I would think this guess is reasonable.

 

Thanks Mike, I follow your logic but seat-of-pants tells me that it's not quite accurate. I was running 450/650 springs in my old 996 cab and it was substantially stiffer than this. Granted, different suspensions and dampeners feel different anyway but I'd guess the springs are more in the mid-high 300 to low 500 range. Obviously a difference front to rear given the weight differential. Hopefully we'll eventually get some real data from the technical documentation on the GT3 or maybe H&R. Does anyone have a good contact there?

 

Paul Frere's book The 911 Story, 7th Ed. gives wheel rates for the GT3 and GT2 on page 423. His data are in N/mm and I have converted them to pounds/inch. Since these are wheel rates, actual spring rates would be somewhat higher due to the motion ratio of the suspension. These rates are presumably for Mk 1 GT3.

GT3: Front 196 Rear 363

GT2: Front 223 Rear 463

BTW, a normal C2 is given as Front 165 (M030 184) Rear 229 (M030 279)

 

That looks like a great book - I think I'll have to get it after I make my way through Excellence... a little more. Looks like that book has more technical specs in it.

 

Bob, the rear springs are progressive which makes judgements by feel difficult. With no cornering load or over small bumps the car will feel softer than it will in cornering or over larger bumps. Take a look at this picture. The progressive, upper section is very tightly wound compared to the lower section. A single spring rate characterization may not due justice to the design.

 

Hmm... good point Mike, although there's not much travel left of the progressive part in that picture. I guess what I'm looking for is the max spring rate. I can still pretty definitively say this car is not as stiff as my old car - on street or track.

BTW - is the GT3 RS really running 1800 pound springs?

 

Cupcar - any idea of the conversion between wheel rate and spring rate on a GT3 suspension? We'd need the motion ratio and travel factor to get the bulk of it. There can be a pretty big differential on some cars but I suspect from looking at the GT3 suspension it's not much - at least on the rear it looks pretty direct? front might be a little more due to the angle of the spring off of vertical?

I know this is a rathole but maybe at least an educational one...?

 

Really I don't know, I would guestimate that the rates are close to what they have run on past RS cars ~250 front and ~450 rear spring rate for the GT3.

 

Front is still McPherson strut on 996, isn't it? If so, motion ratio is 1:1.

 

OK, that's good to know. Judging by looking at the linkages it looks like a direct relationship front and rear so that makes sense. There's no real leverage point per se at least.

So I guess there's just a slight factor for the angle of the front shock but that makes a negligible difference as I understand it.

Thanks, now if I can just find the wheel rates or spring rates for the new GT3 I'm in business

 

According to the article in Sept Pano, the GT3 street has 40 N/mm linear front springs and 95 N/mm progressive rear springs. This equates to 228 lbs/in front and 542 lb/in in the rear. In comparison the 2003 GT3 Cup has 1370 lb/in front and 1484 ib/in with 342 ib/in helper springs.

Karl

 

Thanks Karl - that's a big help. I'm surprised to see such a huge split front to rear even with the rears being progressive. Thanks for the Cup car rates - that's a good data point too.