Does anyone know definitively what the spring rates are for the PSS9 coil overs? When you list it, please identify which variation of the PSS9 it is. Some of you sponsors who carry your own specs please chime in if possible.

By Design: When you guys set up that Cab with the JIC coilovers for the shootout, what spring rates were you running?

My gut feeling is that spring rates aside, the valving for the JIC dampers are much more aggresive than the PSS9s. I need to do more research to determine if going to 7/10kg (F/R) springs will cure the harshness on the street, or whether the valving are my limiting factor.

Thanks,
Stephen
'01 Turbo Ti
455rwhp, 505rwtq

 

Since 7kg/cm equals 40 lbs/inch and 10kg/cm equals 57 lbs/inch, is it maybe a 70 and 100 kg/cm spring you'll looking at??

 

Just as Cary alludes to, non-progressive spring rates are specified as pounds/deflection. I will assume his calculations are correct and agree in saying something seems amiss. Stephen, I suggest you recheck your information.

It is very easy to measure spring rates for non-progressive springs. If the spring is out of the car, it is simply a matter of accurately measuring the elastic deflection (compression) of the spring when subjected to a weight of known value.

Wouldn't it be great if this information was readily published and available?

 

Actually, they are 7 kg/mm and 10 kg/mm springs, not per cm.

It's been a long time since school, and correct me if I'm wrong, but to find the lb/in of a kg/mm spring, I multiplied the kg/mm spring by 2.22 lb/kg, and then again by 25.4 mm/in... that gives me lb/in. The entire multiplier is 56.388 lb*mm/mm*in.

As a reference point, here are some measured spring rates per PCA:
OEM: 146/203
OEM Sport: 170/260
H&R (progressive): 180~240/250~295

JIC spring rates are (kg/mm: lb/in):
7/10: 395/564
8/12: 451/677
10/14: 564/789
12/16: 677/902
9/12: 507/677

I've currently go the 12/16 (front/rear) setup, and while they are rock solid for the track, they aren't streetable... at least here in Chicago. I've got replacement springs sitting here of 9/12, and am also considering 7/10. However, I am wondering if the valving of the dampers could potentially be too aggresive for softer springs to reduce impact harshness. It may be that my limiting factor is not the springs, but valving. Hopefully, Perfectpower can shed some light on this, as I hope to get Sol to drive it around the block a few times to give me a second opinion.

In the mean time, I was curious as to what the spring rates were for the other coilover setups out there. I just find it a little surprising that all these coilovers have been sold, and yet, nobody knows what specs they've purchased. Hopefully, you guys can shed some light on this.

Thanks,
Stephen
'01 Turbo Ti Upsolute
455rwhp, 505 rwtq

 

Stephen,
You are correct with your conversion. I cannot believe how much stiffer than stock JIC rates are

I am also very interested to see what the rates are for the Euro PSS-9's, the US PSS-9's, the RUF PSS-9's and the FVD PSS-9's. I will bet you we never collect this info though.

 

Yeah... the rates are so high that they sometimes don't register til you take a second look.

Hopefully, somebody will chime in with some spring rates.

 

"In the mean time, I was curious as to what the spring rates were for the other coilover setups out there. I just find it a little surprising that all these coilovers have been sold, and yet, nobody knows what specs they've purchased. Hopefully, you guys can shed some light on this."

Stephen,

Great questions. I believe the answer is less than 1% know their spring rates. Most don't now what the spring rates equal or what a certain rate will translate into what type of handling, ride comfort, etc. Big choice and trade off in these departments. Like so many people I have met regarding their power modifications......they are estatic with the results until they have a chance to compare it with other cars. Then they either blindly defend what they purchased or get all upset at whoever they bought it from.

In many cases (not all), the curent favorite tuner is the one with the best marketing and/or PR program.

 

I couldn't agree more. Perception is 99% in many cases, especially when dealing with people who don't do their own research. Most people are not that deep in automotive knowledge and experience, and yet, they want what's best for their cars for handling, power, looks, etc... and while there's absolutely nothing wrong with that (we're all like that), the problem then is that they have to rely on others' experiences to make their own decisions in terms of performance, as opposed to researching the specifics.

So, if a shop is favored on a forum, they will be perceived as the "best"... sort of a lemmings effect. Luckily, we do actually have a bunch of decent people and sponsors on this forum.

Now, back to my question... if the end customers don't know what specs of equipment they are running, surely the vendor who sold them should be able to contribute, yes?

I doubt fear of copying one's product would be the motivation as to not stating the info, as there are many factors that go into a set of coilovers... valving (arguably more important), type of springs, damper construction, bump stop specs.... heck, even two same-spec'd springs from two dif manufacturers can behave differently on a suspension dyno.

I don't want blue prints... I'm just curious as to what are some of the common spring rates out there. That's like wanting to know if the potential house you're interested in has a 3-car or 5-car garage. Personally, I wouldn't buy a product if I can't have even the most basic of specs, but that's just me.

Stephen

 

Hi Stephen,
I look forward to a test drive in your car on Wednesday. I believe you should have a maximum of 650 lbs/in in back and 400 lbs/in in front. These are race car rates, but on a heavier car. Lower is better for the street. Bumps will prevent your sticky tires from staying in contact with the ground if you're too stiff on the track or on the street. That said, the valving should be fairly UNagressive on compression but able to stop the bounce on the rebound. JIC should help out with a dyno sheet for your shocks. I'm embarrassed to say that I have never checked the spring rates of the various PSS9 spin-offs even though they've passed through my hands. I'm sorry. I have found that less compression damping and more rebound became Porsche's direction in the late 80s and early 90s, though.
I am quite sure you will be a lot happier if you reduce your current spring rates and soften the shocks up accordingly. Don't forget, anti-sway bars can be very effective in getting the desired result without overdoing the springs/shocks.

Sol

 

Our previous conversations have been very informative, and I am definitely looking forward to checking out your shop on Wed, as well as getting your opinion on my future setup. The sooner I take care of this, the sooner I'll be able to finally get the Perfect Power alignment and corner balance that I've been waiting for.

I'll buzz you on Wed before I leave the Loop. Talk to you then!

Stephen

 

If anyone has any of the PSS-9 spring variations (Bilstein, Ruf, FVD), or other manufacturer's springs, out there and are willing to pay for two-way shipping, I have the means to determine spring rates. I would welcome the opportunity. It could be a very good resource for members. Since I also possess my OEM springs, I can also determine their rates as well. This will produce a valuable database.
I would only need one front and one rear spring of each type.

Takers?

 

According to the shop manual the stock spring rates are
Front: 33 N/mm = 187 lb/in = approx. 3.3 kg/mm
Rear: 60 N/mm = 340 lb/in = approx. 6 kg/mm
Perhaps the PCA published rates are measured at the wheel rather than at the spring.

 

I believe they did use a suspension dyno to arrive at those numbers.

 

I would like to know the rates of the factory 030, X74, GT2, and GT3 springs as well as the current USA PSS9.

 

Most of the springs I"ve checked have been about 350 to 400 lbls in the front and 500 to 600 in the rear. I haven't checked any PS9s for over a year and I don't know which model PSS9 I checked but some of them were RUF factory cars if that means anything. If someone has any of these springs that they would like me to check send me a PM and I've give you my address. I have all the equipment to check them and then I'll post the results and return the springs.