ZDan

I'm buying a 987.2 base for street/track duty. I'm looking at lowering springs to stiffen things up and bring the car down a bit. I've searched but can't find *any* data on spring rates! Ideally I'd like linear-rate springs about 20% - 40% stiffer than stock, would be nice to have relatively more stiffness added up front to take advantage of increased front camber (planning on GT3 control arms).

Any data on rates for lowering springs for the 987 would be greatly appreciated!

Thanks

andy7777

Doubt if that's published anywhere, or if it means anything.

Try the X73 suspension, or for your car, the Cayman R shocks and springs. Your drop will be 20mm and you will have the firmness you want without the hop and judder of mismatched shocks and springs.

A432

^ This....the R shocks/springs have a few minor limitations but, for most dual purpose street/track cars, it's a great setup

ZDan

Appreciate the input! I'll think about R springs, anyone have spring rates for them?
Also, what's a good source for factory Porsche springs?

I'm considering PASM springs as well, which are (I think?) 22% stiffer in front and 15% stiffer in back vs. non-PASM, and should lower the car 10mm. If R springs lower 20mm and that stiffness or stiffer that might be the sweet spot for me...

I'm planning on keeping stock dampers as I'm up against the wall on mod points without adding significant ballast weight. Also I am cheap. Also I might ultimately go up a class and get coilovers anyway so trying to minimize $$$ spent and effort expended.

Regarding increasing spring rate without changing damping:
It should be noted that damping would only have to go up with the *square root* of spring rate, not linearly, to maintain the same percentage of critical damping. So if spring rate goes up by 30%, you'd only have to increase damping by 14% to stay at the same damping relative to critical. That's why lowering springs that are somewhat stiffer work OK (generally) even while keeping the same dampers.

I did this last year with my daily-driven BRZ PP, replaced factory springs with ~40% stiffer Swift springs while keeping the factory dampers. The car performed very well at the track, I won my time-trialing class over a similar BRZ on Ohlins (also over a slew of Miatae).

A432

From Cayman S springs, the front is increased from 27 to 30 N/mm and the rear is increased from 37 to 43 N/mm.
The front R shocks also have an additional internal helper bumper that adds 11 N/mm under compression. This is in addition to the bumpstops.
Without getting into a long suspension debate, consider that critical damping is a small part of the equation while you're also lowering the car (car specific angles and travel to bumpstops)
and as a result affecting the car specific roll centers at the same time. The R setup is a factory tested system that works well with the Cayman's suspension geometry.
When you start going lower than that, roll center issues start happening driving other compromises or requirements.

andy7777

Ha, what A432 said, except he said it from an obvious base of knowledge and I from seat of my pants and having messed with suspensions over the years of tracking several cars .

But having gone through just doing springs to coilovers to fully adjustable systems for several cars, I'm pretty satisfied that you're far better off going with a factory setup than mixing and matching unless you go all the way for a track setup with fully adjustable stuff, and then better know what you're doing actually adjusting .

So unless you go for the shocks as well as springs, like in the x73 setup, you're far more likely to end up with some characteristics you're unhappy with.

ZDan

Ah, great info! So here's what I have:
987 non-PASM: F = 27 N/mm, R = 37 N/mm
987 w/ PASM: F = 33 N/mm, R = 46 N/mm, -10mm ride height
987 Cayman R: F = 30 N/mm, R = 43 N/mm, -20mm ride height

I got feedback on Eibach and Vogtland springs, was given two rates for each, so they're either progressive or dual-rate.
Eibach: F = 18-34 N/mm, R = 26-50 N/mm, -30mm ride height
Vogtland: F = 18-30 N/mm, R = 30-35 N/mm, -30mm ride height

Ideally a factory-developed setup is what I would go with. But springs are about $350 while a full R suspension is about $2400.

I'm pretty OK with taking a chance on just springs. Just have to decide which ones...
What is a good source for factory Porsche springs?

A432

I think Eibach/Vogtland/H&R are all about the same and the 30mm lowering may be marginal. You might be able to find a lightly used R/Spyder suspension set for $1K or R/Spyder springs for say $200.
Also, check the rules for retrofitting shocks in your class. Often there is a clause that says it's legal if it came on a factory version of the model.

ZDan

I don't have enough track time available to me to optimize fully-adjustable high/low rebound/compression damping anyway! Single-adjustables or no adjustments at all is fine with me...

Quick search showed an X73 setup for 981, is there one for 987? What spring rates and where to buy?

Thanks!

A432

The R/Spyder suspension for the 987 was basically called X73 for the 981.

ZDan

Thanks, I'll start checking around for used.
Regarding rules, it's certainly worth asking the question! Would be nice to get the car lower and stiffer without any points/ballast weight at all

A432

Yup, you might be able to do something like a Bilstein Sport replacement shock or R/Spyder shock as factory offered replacements in the rules
Not sure if the Sport replacement has the same perch height but I think it does. Also a rumor that the Bilstein Sport replacement is the R shock, need to see a dyno.

ZDan

Big thanks to you guys for quick and on-point information and advice

Checked with the rules guy, swapping factory-optional parts for a given model is a 0-point mod. Since PASM is available on the base car, PASM springs are a legit 0-point swap for me However, since the R is considered a different model, swapping parts from it would add the same points as aftermarket parts (+2 for springs, +1 for dampers).

So optimal decision seems to be ~15-20% stiffer and 10mm lower factory PASM springs for 0 points.

So what's a good source for buying factory Porsche springs? Looking for used ones but so far with no luck...

A432

Search here on the (3) sales areas and at planet 9. Also, put up a WTB ad at both places because someone has these laying around but simply hasn't thought to sell them.
Might find the springs also on fleabay but I wouldn't buy shocks there unless the seller was extremely reputable.
Surprised PASM damp. are 0 points with ability to retro and reprogram. Guessing the guy that just won a title was doing this.

ZDan

"Member For Sale" ads, + "Parts Marketplace", what's the 3rd one?

Rules don't single out PASM-equipped cars anyway. Probably should... Maybe PDK as well, reportedly worth maybe half a second? I got a manual though...
We haven't had a whole lot of stockish Caymans running with the club so points system doesn't account for details of options...
What guy that just won a title you referring to?
Club is COMSCC, we run Palmer, NHMS, WGI, Thompson, sometimes Mosport, sometimes Mont Tremblant...