Slakker

I recently went through the process of adding JRZ 3-way Remote Dampeners that were for a 996Cup car to my 996 C2. It was quite a learning process and so I thought I would document as much of it as I could remember. Just getting them assembled was a challenge. In addition to needing springs and helper springs, I couldn't reuse my existing mounts because the top of the shaft on the JRZ's are 14mm where as my Moton clubsports were 12mm. I either had to drill it out or order a custom set from Tarrett. I chose the later. I also had to get rear sway bar mount brackets from them while I was at it.

The biggest challenge with the Cup shocks is the rear. Initially I didn't think this would be an issue because I was also upgrading to 996Cup wheel carriers. I was wrong. The Cup wheel carrier did not change my geometry at all. So I abandoned them and went back to the C2 carriers.

The front Cup dampener has a stroke (distance of travel) of 5.25" but the rear only has a stroke of 3.5". So if you allow for 1.5" of droop (how far it compresses from the cars weight), that only allows 2" for the shock to work. So you can't adjust the ride height in the rear by changing spring length because there is no extra shaft travel to play with.

The solution, as seen elsewhere on RL, is a spacer between the rear shock mount and the chassis. I purchased 2 - 1" slices of 5" aluminum rod from the local metal store. I also bought a $70 drill press at harbor freight and a 2.5" hole saw bit. It was painfully slow to make but it worked very well.

For springs, I went with Olsen's recommendation of 5"-900# mains with 2.7" tenders for the front and 6"-1000# mains with 2.7" tenders in the rear.

A good target cup car ride height is 3.75" front and 4.6" rear. My final ride height was 3.35" front and 3.6". Part of this is because the car is lowered .5" at the subframe from installing solid bushings. But the results were awesome and the car felt amazing.

Evil Bunny

Thanks for taking the time to post and sharing your experience :lowdown:

Could I ask how firm the ride is with your quoted spring rates? Are you able to drive the car on the street?

I notice your main spring lengths are 1 inch longer, front & rear than that specified by Porsche on cup cars are you able to share the thinking around this? Suspension dynamics are not my thing!

Do the longer springs bring a benefit to the C2?

Have you had any issues with the longer springs working with the damper piston lengths?

Have you ever run out of travel at the rear?

Do you have any idea what the maximum ride height achievable is with your setup? Would GT3 levels be possible if desired? (F; 115mm/ R; 130mm)

Thanks again

Slakker

It was awfully low for a street setup. As for the ride height, the rear was adjusted as high as it would go(which wasn't much) and the front was adjusted as low as it could go to maintain what little rake I could get. Tim Olsen did the calculations on the springs for me. One key piece was that the spring stiffness was partially due to the fact that I had no rubber in the suspension. It was all monoball or heim joints.

nckwrnr

For the fronts did you use anything on the shocks to attach the brake lines?

Slakker

I didn't and didn't have any issues.

nckwrnr

Thanks thats good to hear. I have a set I am installing now that dont have the bracket.

Evil Bunny

Slak

Could you post a picture of your front sway setup, I notice you have no brackets on the damper, are you using the pinch bolt on the carrier/upright to attach the drop link?

Slakker

Yes. The adjustable front droplink includes the pinch bolt for the carrier. I don't have a good picture of it though.

Evil Bunny

Thanks

Do you know of any performance advantage / disadvantage of using the pinch bolt location versus a damper bracket?

Slakker

No. I've had someone try and explain to me that geometrically it's an advantage to attach higher. But none of the racers or race shops I know advocate it. Remember, the only thing that matters in a setup is the one that will give you the greatest confidence and predictability. There is a very high likely hood that you will not be able to tell the difference in the sway bar attachment point.

ScottArizona

Old thread I know, so I apologize for the bump, but Slakker, I'd love to pick your brain about your rear top spacer design (your pm's are full). Did you just drill three holes and source longer bolts to insert through the top mount, through the diy spacer, and into the body for attachment from the inside? And then just cut a hole through the center of the spacer to make room for the top mount attachment and adjustment stuff? I haven't yet taken my car apart so I'm just trying to get a sense for what I'm going to have to do before I jump in. Thanks!