Fast4525

Time to make some decisions about what suspension parts I will need on the C2! The car will be used 50/50 for street "fun" driving and the other half will be spent on the track with the odd Auto-X thrown in. I will use Hoosier R6s for track/Auto-X and Michelin PS2s on the street.

My idea is to use the excellent-handling Carrera RS as a starting point and hopefully improve a bit on what the factory did 15 years ago! The RS is listed in various places as having either 200/400lb or 227/440lb springs.

I have researched all the common options and I think that I have narrowed it down a bit. Ideally the parts budget should be under $3500.

-Bilstein HD with H&R red. Too soft.

-Bilstein PSS9. Not a huge fan and too soft.

-Bilsteins with custom valving and stiff race springs (maybe 275/500). This is very appealing to me but I have no idea what the cost would be, who to contact for the custom Bilsteins or what springs brands to look at.

-H&R coil-overs. Decent but the spring rates seem too soft.

-KW V3. Nice stuff but the springs seem too soft (170/445) and the F to R balance seems out of whack. Maybe I could spec 225lb front springs?

-JIC. Quite popular on this forum but I have never like the feel Japanese dampers. Does anyone know what springs rates they use?

For sway bars the obvious choices are genuine RS bars or TRG bars and I am leaning towards TRG because of price and the larger rear bar option. Any reason not to get the TRGs? What end links would be best? I'd like some with sealed ends to reduce unpleasant noises.

Other big questions are ----- camber plates, various suspension bushings and something to address bumpsteer on the lowered vehicle.

I know that I've asked lots of questions but I need to start somewhere

Any advice is appreciated.

donoman

I currently run Bilstein HDs with H&R Reds. Personally I wouldn't go with anything stiffer on the street. I'm coming back from a stiffly sprung Miata that would jar my fillings and to me, it just wasn't worth it having to drive up 2.5 hours to the track going 60mph because I was just so uncomfortable with the springrates.

But to each his own.

Definitely upgrade the sway bars. I am running stock sway bars and the car looks like it's 2-wheeling in almost every turn I take at the track.

chancecasey

Send me your car and money and I'll make it all better.

Marc Shaw

I have H&R street performance coil-overs and find them too soft for 75% track use (250/300, IIRC). I will be installing JIC coil-overs with 9/14 (500/800) springs so I'll report back next year (ViperBob's recommended setup).

The JIC's come with camber plates.

ERP A-arm and trailing arm spherical bearing and spring plates are on order but I hear good things.

TRG sways (23/25mm) are great but just watch the collars don't loosen up - can be used with stock drop-links.

Marc

Hoosier_Daddy

Tough call as we all have such different tastes...

I have 700/900 spring on single adj. JRZ's, TRG bars and for me it's fine for the street. I also have fairly reasonable roads and a wickedly understanding wife who lucky for me is a PCA instructor.

So... on the street it's fine and at the track... well...

Good luck - this is the fun stuff.

HD

ThomasC2

I agree. I have 900/1100 springs and think it works OK on the street...but that's me!

Geoffrey

As a point of reference, I have 600/650 with JRZ triples on my racecar running slicks. My experience with 964s suggests that you don't need to go so stiff and that the F/R split is not as great as some think.

Hoosier_Daddy

I would guess your race car is a lot lighter than my 3200 + lb C2...

Bill Verburg

Here's a compilation of spring rates that i've collected, mostly here

joey bagadonuts

Very interesting. So what is the best manner to determine springs rates, Geoffrey (or anyone else)? Are there any tests you could do at the track to confirm you have the right variance between front and rear? Something a bit more concrete than seat of pants like pyro readings and lap times? I think many of us tend to modify our setups to get the right balance, i.e. varying tire widths, camber, toe, sway bar settings, shock valving, etc. but it seems that if you start with the right spring combination you could minimize some of this tweaking.

I imagine that track conditions and driving style factor into the equation, as well, but there should be a systematic approach to determine if you're running the right spring package for your car and your driving style.

garrett376

Funny you say that Geoffrey! On my C4 race car, at one race I ran at Buttonwillow I had 300/450 springs; then next time I was there I had 525/800 springs with nothing else changed - I was faster with the softer spring rate!!!!

Marc Shaw

But Bill's data would suggest that the RS and Cup cars had quite a large f/r split - did Porsche get it wrong?

Marc

chancecasey

I believe the general rule of thumb is spring rates should be about proportional to F/R weight distribution. Of course you can vary this to accomplish several things.

I plan on 400/550 or somewhere thereabouts on a 2375 pound 964 with me in it.

Also remember the wise saying (can't remember who said it) that any suspension can be made to perform *reasonably* well by stopping it from moving.

I would focus on the spring rate you want first and then get dampers that are suited to that rate. Most adjustable shocks only have so much of a range of adjustment, that you quickly get out of range by drastically changing spring rates. I'm sure there very expensive very nice ones that have a larger range of adjustment but I don't know.

race911

Yep. RSA #1 was spec'd by Kiwi Dave (Taylor) when he was at Racer's Group, and it was pretty soft, all things considered. Everyone said I was nuts, blah blah blah. Just some single adjustable Protracs and pretty even f/r spring rates.

Worked fine and had enough race results running even or in front of cars with much more exotic equipment. If/when I ever put the current one together I'll certainly use the same stuff.

Mark in Baltimore

I have 700/900 springs on my Moton-equipped 993. The car handles beautifully, but I had notions of eventually upping the rate to 1100/1300 and go with smaller bars (have TRG's now). I decided that I was going to leave well enough alone and just continue to drive better, for the relatively softish springs I currently have make the car very communicative in my fumbling hands.