Ed Newman

Until now, I thought I was running very stiff springs 1100/1300 lb-in in my 996 C2 set up like a mini-cup. That was until I burned through my left rear tire. It was rubbing on the top of the wheel well as I bottomed the car out on the right turns in and out of the infields at Pocono. That would mean I was compressing the spring over 3" till it basically was solid. Not a good thing. A 997 GT3, also with a Moton setup and slightly softer springs had the same problem. I was quite suprised to see the cup cars did not. When I got home today, I looked up the spring rates for the 996 cup car. If I do my calculations correct 240/260 n-m is about 2100/2300 lb-in. Does that sound correct? If so, it may also explain why my car seems to have so much body lean and is always carrying the inside tire. Any thoughts?

amondc

Not sure how to read the data but they have it listed for the 997 as

Front:
Main Spring 100-60-260
Helper Spring 75-60-43

Rear
Main Spring 120-60-260
Helper Spring 60-60-40

I don't have the 996 manual on this computer to check right now for you

Chris

JimB

The 2005 cup manual says:

Front
Main 100/240/60 (240 N/mm)
Helper 75/60/43

Rear
Main 130/260/60 (260 N/mm)
Helper 60/60/50

I'm not sure what this converts to in Lbs. I know the 996 cup isn't very stiff. My 996 stock class car has adjustable GT3 RSR springs that are set at 1600 f/1800 r. It's much stiffer than my cup car.

Greg Smith

IIRC you multiply Nm/mm x 5.7

Larry Herman

Yep.

Ed Newman

Ok, so 5.7 is the correcttion factor. The N-m vs N-m/mm thing was confusing me. So if I go with Cup rates of 1368/1482 and factor in the additiona weight of my car 3050 vs 2550 (call it 20%) I would see 1600/1800 which is what Jim is running That would be about a 55% spring to weight ratio. Sounds like a plan.

Geoffrey

To read the values on the spring (100/60/240), the first number is the spring length of 100mm, the second the diameter of 60mm and the last number is the spring rate or 240nm/mm.

Larry Herman

Ed, one thing also comes to mind, and that is when I saw you scrubbing in your tires at the Glen race, you were actually lifting the front wheels almost a foot in the air when you carved back and forth really hard. It looked quite scary. Going with Jim B's setup sounds like a good plan.

JimB

And Larry's seen the back of my car a lot so he knows what he's talking about!

Larry Herman

Ho, ho, ho. You never let me return the favor at the Glen.

JimB

You got me there. It would have been great to run together at WG. I think I'd have had the advantage from T10 to T5 but you would have kicked butt from T6 to T10. I predict I would have won the race but been DQ'ed for flagrant blocking.

David K.

Worked for me......

2000gt3cup

Ed remember that is what I thought I saw on Saturday at Pocono...again great time running with ... hopefully we can hook up again soon

Ed Newman

Ok, I am ordering 1600/1800 and we'll see how it works.