Autox Spring rate help, Too Stiff? Options

[nolift914]

Is my Autox 914 too stiff?
I am currently running the PO setup, the 914 was set up for club racing with front and rear coil overs. The front is at 330lbs/in which I believe is the equivalent to 25MM torsion bars and the rear is at 230. The 914 is a 4 weighting approx 1780lbs with bias ply slicks. I plan on switching to Dot-R radials. I have always thought for autox go soft on springs and big on bars. Does the paddock crowd have any suggestions for a setup. The autox sites in NYC tend to be on the rough side. I was thinking either 175 lbs/in in front and 140 lbs/in rear or 200 lbs/in front and 180 lbs/in rear.

[nolift914]

Is my Autox 914 too stiff?
I am currently running the PO setup, the 914 was set up for club racing with front and rear coil overs. The front is at 330lbs/in which I believe is the equivalent to 25MM torsion bars and the rear is at 230. The 914 is a 4 weighting approx 1780lbs with bias ply slicks. I plan on switching to Dot-R radials. I have always thought for autox go soft on springs and big on bars. Does the paddock crowd have any suggestions for a setup. The autox sites in NYC tend to be on the rough side. I was thinking either 175 lbs/in in front and 140 lbs/in rear or 200 lbs/in front and 180 lbs/in rear.

Currently running 19mm torsion bars with a smart racing bar, with the smallest diameter bar they offered. Had under-steer until I went to the lightest smart racing bar. Front shocks are Koni's set to almost total soft. Rear springs are 240# if I remember correctly. They might be #225, but will check.

With Avon's no under-steer at autox's or hilllclimbs. I'm 100# ligher than you.

Are you going to Dot-radials to make a class?

I am currently running in PCA class M01 and SCCA FP, I am looking to move away from the Canti's due to the limited availability. Cant find soft compounds.
Going to either Radial slicks or Dot-R autox tires. I found this chart listing the front torsion bar spring rate

SIZE ( mm) SPRING RATE ( Lb/in)
18.8 110
21 173
22 210
23 250
24 296
25 350

I believe I have 330lbs / springs on the front which by the chart would be the equivalent to 24.5mm bar, which seems stiffer than those listed in this thread from 19mm to 21mm.

There are some mine fields with a suspension set up like I related..

A stiff shassis is needed to *make the suspension do its work*......I'm talkin' bridge stiff. A stock chassis will flex all over hell and make handling inconsistent.

To help the suspension do its work, low friction bushings....not cheep derlin/poly whatever, are needed.

Over 200 lb rear springs can/will cause cracking aound the un-reinforced rear towers long term.....the rougher the venue, the quicker this happens.

Enjoy (IMG:style_emoticons/default/biggrin.gif)

J P

I should have given more details of the 914's current setup, In addition to the front and rear coil-overs on Bilsteins, the front struts have raised spindles. front and rear Elephant racing polybronze bearings, Reinforced rear trailing arms and lower console, full 8 point cage. no reinforcement on front and rear shock towers. Front sway bar (Weltmeister) and no rear bar.

From the setup's listed everyone is softer in front between 125lbs to 175lbs and stiffer in the back 225 to 275. (IMG:style_emoticons/default/confused24.gif)

[mskala]

I believe your chart is accurate from my memory of 21mm calculation.

Anyway, what do I know, I've never driven anything other than the 914
in anger, but here is my opinion. Yes, you should have the front softer
or equal springs to rear. Since your car is not a street car, overall
stiffer is better, except when the surface gets too bad. Understeer is not
your friend, and can be tuned a bit with the front bar. Also, unless you
have a co-driver, with such a light car it may be difficult to heat up the
tires if you go with something wide for your semi-flares. We do a group
of 4 runs and the first 2 for me are only for heating. If lucky the pressure
goes up by ~4psi then I know I'm in business (with dot-r).

Here is my setup, which I'm pretty happy with as a street car.
Torsion bar: 20mm (yes, these are occasionally available)
Rear spring: 180
Front sway: 19mm weltmeister, set kinda in the middle after tuning
Rear sway: none
Front shock: koni adj
Rear shock: Bilstein non-adj (perch adjustable)
Wavetrac limited slip
about -2deg camber all over
lowered slightly, no spindle change
Wheel: 7.5x16 Fuchs-center, BBS rim
Tire: Kumho V710 215/40/16
No flares
Weight: stock but no tar on interior (~2050)
Engine: 2.2L 'E' six

[nolift914]

I believe your chart is accurate from my memory of 21mm calculation.

Anyway, what do I know, I've never driven anything other than the 914
in anger, but here is my opinion. Yes, you should have the front softer
or equal springs to rear. Since your car is not a street car, overall
stiffer is better, except when the surface gets too bad. Understeer is not
your friend, and can be tuned a bit with the front bar. Also, unless you
have a co-driver, with such a light car it may be difficult to heat up the
tires if you go with something wide for your semi-flares. We do a group
of 4 runs and the first 2 for me are only for heating. If lucky the pressure
goes up by ~4psi then I know I'm in business (with dot-r).

Here is my setup, which I'm pretty happy with as a street car.
Torsion bar: 20mm (yes, these are occasionally available)
Rear spring: 180
Front sway: 19mm weltmeister, set kinda in the middle after tuning
Rear sway: none
Front shock: koni adj
Rear shock: Bilstein non-adj (perch adjustable)
Wavetrac limited slip
about -2deg camber all over
lowered slightly, no spindle change
Wheel: 7.5x16 Fuchs-center, BBS rim
Tire: Kumho V710 215/40/16
No flares
Weight: stock but no tar on interior (~2050)
Engine: 2.2L 'E' six

Thanks for the info, you were very quick at the Zone 1 autox. I was having a hard time trying to get heat in the the tires and was looking forward to trying to close the gap on day 2 before the apparent issues.