912-6 Track setup - bar size

jhelgesen · 03-06-2006, 07:00 AM

It's time for the 912-6 to take the next step toward dedicated track car. Had a hard time keeping the front end on the ground at CMP this weekend, so the plan is to continue the suspension upgrade.

I'm going to go with bilstiens HD's all around, send them out for valving eventually, but start at out of the box right now. I'll also remove the stock sway bars for adjustable units.

I'll be pulling out the 21 hollow/26 turbo torsion bars for a stiffer set. Looking at a few combinations, looking for opinions on sizes.

Thanks!

SandyI · 03-06-2006, 08:11 AM

What size wheels/tires are you running?

Eric P · 03-06-2006, 08:38 AM

You have a 7mm difference on the first 2 choices but then the last one is an 8mm difference. Why?

I started with 20/27 and now have 23/30. That ratio (7mm) seems perfect.

jhelgesen · 03-06-2006, 08:56 AM

I'm running 7 and 9x17s with 205/50 and 255/45 (I think thats right) tires.

Ratios came from Elephant racings web site.

Eric P · 03-06-2006, 09:17 AM

I'm guessing your rear was way too soft compared to the front with your 21/26 setup (hence your handling trouble). Frankly, any of your 3 choices would be an improvement. 23/31 is going to be damn stiff (which is fine if that is what you want) and your shocks will be key to managing them. Going from 21/26 to 23/31 isn't a STEP to a track car, it is a leap IMHO.

I run 7x15s and 225/50s all the way around and like the 23/30 setup. Don't know what your larger rear tires mean for setup...

304065 · 03-06-2006, 09:37 AM

Big as you can go. It's impossible to get enough spring rate in a Torsion Bar 911 (which is why the factory went to coils in the early 70's)

jhelgesen · 03-08-2006, 05:18 AM

That wasn't too hard, I have a set of 23/31's on the way to the house. Next step, sways and shocks.

Eric P · 03-08-2006, 05:25 AM

Cool. Let us know what you think of the HDs. I went straight to custom valved but still wonder what the HDs would have been like.

If money IS an issue, you may consider doing an adjustable front sway first and leaving the stock rear. That is what I have and it is a good setup. I read some guys have VERY small rear sways or even none...

304065 · 03-08-2006, 05:37 AM

John:

If you go to 23/31, you will definitely need to change the shock valving rate to match the uprated bar. A 31 rear torsion will require a shock valving that is way beyond the Sport, and probably beyond the "Rallye" option.

There are a couple ways to go about this. One is to return the torsions you bought and buy the Smart Racing package, which includes torsions, antiroll bars and four revalved shocks that match the spring rate. It's not that expensive, like $2300 or so.

The second way is to have a local shop use their proprietary knowledge of valving rates and send the shocks to Bilstien to be revalved. Most shops guard the rate as a trade secret. Alternatively, you can call Jack French at Bilstein and ask him his recommendation.

The final way is to go all-out and buy the Fox Shox which are adjustable. This will allow you maximum flexibility to tune them, but a longer learning/testing curve. But if you want the maximum speed out of the car, this is the way to go. The adjustable front spindles are illegal in PCA stock.

jhelgesen · 03-08-2006, 06:43 AM

Think I made a mistake specing Bil HD's, should be sports.

I've been watching Smarts and Elephants web sites. I can pick and choose what I want from Elephants site, looks like I can do the same from Smart. Hope to order a set of shocks and have them valved to match my setup, just have to decide on some sway bars.