Talk me though rear shock options.

[Driven97]

Well, my car has a fresh lease on life. Made a bunch of changes, and it's now an autocross animal.

Current rear shock is the OE Bilstein revalved by Chuck for 30mm torsions with his canned settings.



I've since gone to 33mm rear torsions. (~300lb/in to ~438lb/in.) Quite a difference. Rebound, however, still feels sufficient. The problem is compression. The rear is poorly controlled, car takes forever to set in transition. There's a lot of waiting for weight to transfer. You can see in the dyno plot that the valving does nearly nothing in compression.

So show me some options. Here's what I've found so far, in order of cost:
- Get my Bilsteins revalved (again) for the higher rate by someone who knows AX intimately
- Koni Sports (8210-1159)
- Fox single or triples (from Rebel)
- Ohlins ($$$)
- JRZ / Moton ($$$$$$)
- Purchase the Fox eyelet to bayonet adapter and spec my own baller Penske or Koni ($$$$$$$$$$$$)

Any other options I'm overlooking?

[Dave at Pelican Parts]

I'd forget the Koni Sports, unless you're going to get them re-valved as well. My feeling (no hard data to back it up, sorry!) is that you're past the range of spring rates they were designed to control well.

I'd be surprised if Chuck couldn't re-do the valving again and up the rebound damping. Of course, that raises the potential for downward "jacking", on sufficiently bumpy surfaces.

--DD

[rgofast]

I had Chuck build me a custom set of triple adjustable bilstiens for my the rear of my 69 911 autocross car., as I did not want to cut out my shock tubes to fit fox shocks. These are remote canister shocks with adjustable rebound and compression. I can also adjust the canister pressure with nitrogen and stiffen the spring rate. I am very happy with these. I used Fox racing shocks in the front wich allowed me to raise the spindles and lower the roll center. I also used his hollow torsion bars, and sway bars, poly bronze bushings,quick change spring plates and bump steer kit. It is a very expensive setup, but allows for a lot of adjustability.

[JohnJL]

Hotbits are also an option in double adjustable form. I have a set in the process of installation.

[RichardNew]

Make sure you have the proper spring and sway bar package. You only do shocks when you have those items in place.

It’s critical that you get the spring package right before you start playing with shocks. Once you get the springs right you can start to tune the package with shock absorbers. Koni feels that you should utilize shocks and sway bars as tuning devices only after you get the spring package correct. You don’t start with shock absorbers. Koni suggests that you regard shock absorbers as a precision tool for that final handling correction.

If you go with adjustable shocks you have an really good chance of getting the adjustment wrong.

I use a lot of rebound. The shock engineers tell me I have too much but I like the way it plants the rear under braking.

Here's the whole article from vintage Motorsport magazine.

Richard Newton