dave-C2

I've got a track/street 964 that weighs about 3,050 lbs with driver and a half tank of gas. Weight bias is 60.7 / 39.3 % f/r. Shocks are Moton CS and the car is lowered.

I know there are some who advocate 1000+ lb spring rates, but does anybody have experience with 600 lb front / 700 lb rear linear springs?

It seems Porsche used a variety of sprring rates in the RS vs the Cup Cars vs the Andial cars. Is there a recommened ratio or difference between the fronts and rears - I believe the Cup Car have 550 front / 686 rear (can't find the refrence for that right now), but obviously they are lghter than the stock car.

TIA for any suggestions.

Geoffrey

I run 600/700 in my 2100lbs race car and the springs are on the light end for a car with slicks. The stock Euro Cup cars run roughly 600 / 800 progressive rate springs and weigh 2425 published weight or about 2500lbs actual. I think you want a 150-200lbs split for a car that heavy, especially since you have adjustable dampers. 700/900 is a common rate used as is 800/1000. I'd probably start with the 700/900, espeically if running DOT slick rather than pure slicks.

CarreraCup03

I run 700 - 900 on my car, as Geoffrey has suggested. Seems to work pretty well for me.

Jasko

Running 750/ 1000 linear on my c4. I like the feel. Car runs between 2800 to 3200 depending on the class I'm running in (NASA vs PCA). The springs feel much better in the lighter weight car. I went with the 750 (vs 800)in front because I wanted a bit softer than a C2 for the oversteer.
Dave

dougn

porsche uses around 180/280 lb/in in their M030 for this weight of car for a street set-up. it amazes me that you can use a 700/800 set-up on the street. that implies about 1/3 the deflection that you get compared with a street set-up for any given "movement" in the suspension. seems like it would be just as effective and alot cheaper to replace your dampers with rigid tubes. alot lighter too!!

dave-C2

Doug, since shocks and springs work in parallel, proper tuning of the shock can make fairly stiff springs tolerable on the street - well smooth streets anyways

Thanks for the consensus recommendation on 700/900. I should have pointed out that I have the new Moton CS, which have a bigger rod diameter in the rear than previously - IIRC the rear and front rods are now the same.

Moton says their design uses the pressurized fluid in the shock to add spring stiffness, therefore the main springs can be lighter. The shock pressure can typically contribute about 100 lbs to each corner. So if I understand it correctly, the efective spring rate would be about 800/1000 if the main springs are 700/900.

I'd appreciate comments from any Moton users

Bull

I was really happy with 600/800lb linear springs on my 3100lb car before I sold it. Many friends could not believe the street ride, and the guy who bought it uses it for mostly street, some track. As part of the JIC Cross suspension, it was ideal for me for track and street.

38D

I ran 700/900 on my 3000lbs 964 turbo. Shocks were Bilstein RSRs. It was perfectly streetable on decent roads. The 700/900 split seems to be the best "tweener" track setup to handle bumby tracks like Sebring/Lime Rock and smooth track like the Glen. If you just ran on smooth tracks like the Glen, I'd do something more like 1100/1400

DrJupeman

I won races in PCA C with 600/800 in my Turbo 3.6. As 38D suggests, you might want to run even stiffer if you are on smooth tracks. I wouldn't go stiffer than 700/900 range for a street car.

garrett376

Do you have a C2, or C4?

On my C4 race car (3100lbs off-track weight - me in the car at the end of a race)I've run stock suspension a couple times in a non-wheel to wheel race environment, 300/450 linear springs for one season of racing, then 525/800 linear springs for the past couple years of racing which I like a lot (and have won my class with) - brake dive is much less and it handles perfectly. With the 525/800's on R-compound tires, the car is fine on the street - not much fun, but fine. Since I have a street 964 to drive, I don't mind the occasional street outing, and when I drive the car for several hours to the track, it's bumpy because the roads stink here, but manageable. I have adjustable shocks which is crucial because when they're set towards the stiff end (how I set them at the track) it's unbearable to drive on the freeway for my wife - the jolts are just too harsh and she'll get car sick really fast, whereas with the shocks adjusted to a lighter setting, it's a bouncy ride, but not harsh and she doesn't get ill.

From what I've seen over the years, it seems there is little point going over 900lbs if you don't run slick tires, which you likely will not do (or should do) if you drive the car on the street.

kgorman

+1 - I have the same setup, works excellent. The Cross is adjustable, so one can give it a couple turns to add a bit of compliance. I generally run 3 clicks from max hard rear, and 6 clicks from max hard front these days. My C4 weighs #2810 w/ 1/2 tank.

garrett376

You need a full cage in that sucker to bring it back up to fighting weight!!!

kgorman

hehe. true. I have some other stuff to take out though!

dave-C2

Thanks for more contributions.

Looks like the consensus, for a C2 street/track near stock weight running R tires, the spring rate difference front to back should be 200 lb, with 650 / 850 (+/- 50) being decided by how much street driving will be required, appropriate shocks, smoothness of the tracks and individual preference.

Anyone with Motons have a different opinion?