GeorgeNZ

At a recent track day, I had an instructor drive my 968 racecar and he made the comment that it had very good front end grip, nice balance but had a tendency to squat diagonally in the rear.

Where should I look to make an adjustment?

Fr; 425lb progressives with single adj Konis, std front swaybar
Rr; 29mm TB's, 185lb coils on single adj Konis, MO30 adj rear swaybar

TroyN

Guess #1: rear springs too soft.

mikew968

I run 600f and 700 r on my 968 with SA ledas and the t-bar milled to 10mm (making it of no effect). My car is pretty balanced but the fastest 968 drivers like the car a little loose. I don't think you have enough rear spring. Try going up to 350 to 400lbs rear springs and if you are going to track the car much use linear front springs.

Mike

RedlineMan

Squat diagonally?

As in it seemed to sag to one corner or just drop the tail? I don't understand.

You are just a tad under 300lbs of rear rate, which is not soggy by any means. 425 front is not overly stiff either. I agree that the progressive springs are not ideal. I didn't even know you could get them that stiff. I like linear rate springs myself. You know what you have that way, eh?

Problem is if you start changing rates a lot you'll need to revalve. It's tough when you have limited damping adjustment.

GeorgeNZ

Car is primarily for tarmac rallying (not sure how that translates on your side of the world) so setup needs to be reasonably compliant with reasonable ground clearance. If stiifer rear springs are the first change, what secondary adjustments are likely required to retain the balance?

mikew968

Will SA Konis' valving match a 400# +/- spring?

GeorgeNZ

John - drops the right rear on a lefthander and vice versa

http://www.youtube.com/watch?v=xuVTSY2F0LA

GeorgeNZ

fr and rr Konis were custom valved by PO

M758

well it looks like 29 t-bars PLUST 185 lbs springs.

My count that comes to 300+ 90lbs or so to 390 and therefore a good match for the 425 fronts.

Squat diagonally? Let me ask another question.
Where on the track? Corner entry, exit, mid corner. Under hard power under straight accel, left or right side?

Problems like this could be due to set-up or something broken or not working right? Set-up looks decient so maybe Sway bar pre-load or a Bad shock?

RedlineMan

Oooops;

Thanks Joe. I goofed. Don't ever look to me for math.

My chart says 29mm = 292lbs. 185lb coil x.56 = 103.6 effective helper = 395.26 total. That is plenty stiff!

The car should not drop its tail with springs that stiff. I'm thinking the compression damping is really weak, and/or the rebound is far too stiff and won't allow the rear to rise again. Another outside possibility is the the front rebound is too light, allowing the front springs to push the nose up, making it seem like the rear is diving. That would be sort of a last gasp guess there, though.

GeorgeNZ

Hmmm....... thanks for everyones input -it has all got me thinking. It appears to be most pronounced on left handers - and it is more apparent at the Taupo circuit which is left hand compared with Pukekohe which is right hand. The last event the PO ran was a 6hr enduro at Pukekohe so could it be a 'right hand setup' behind it? I only got 4 laps in the weekend so didn't get a good chance to try and clarify what was happening ( had to learn the full track).

I think I'll start with getting the car corner weighted - without and with the rear helper springs to isolate any setup/ torsion bar imbalance before pulling the playing around with dampers or changing spring rates.

I do have a pair of un-used Koni3012 with B59 valving for a 944 turbo project that didn't happen that I guess I could try.....