Can anyone give me some ballpark spring rates (Even if it's total poundage so you don't give away trade secrets) for short/bumpy tracks on an early Cup?

THe 900/1000#'s I was running were just too much, car spent too much time airborne and had a lot of trouble in tight corners. Losing 2-4 car lengths in the chicane's and "patient" corners just makes life hard.

THanks,

Chris

 

My Grand Am friends say they've run as little as 400/600 at Sebring, and 500/700 at Laguna which is smooth but slippery. YMMV...

PS: Have you pulled your diff and checked torque on it lately? If you're having to wait to put down power I'd test it and not on the ground. They wear so slowly making it difficult to realize when it's become worthless....

 

What shocks?

 

Dan, JRZ triple adjustables. Just rebuilt and dyno'd.

JGordonSr, that sort of jives with what I've been feeling in the car. Was thinking 650/800 as a compromise....

Ugh.. Diff. No I haven't checked it since I bought the car 6 months ago. Somehow it didn't make it on my list of things to do this winter and having read your post, I'm feeling a little sheepish as some of what I've been feeling could be related. What is a reasonable breakaway torque on early cups? Something tells me it was like 60-80 ft lbs?

Thanks for the thoughts!

 

400/600 seem really low for me. Cup are coming 1300 all the way. 900/1000 is mostly used in Grand-Am.

 

For fast and flat tracks that works. However short bumpy tracks with 2nd gear corners, I'm getting out corned because the car won't set and getting beat to death.

 

Yes, about 80-100Nm for the pre '02 cups.

 

With JRZ triples, presuming your nitrogen pressures are properly set, the spring rates should not be a real problem. They help the car corner flatter, and the dampers are used to smooth out the bumpiness. So I will +1 the "check your diff" suggestion. Also realize that reducing nitrogen pressures in the dampers reduces your effective spring rate...so you can also help tune the car with pressures.

I presume the track you ar etalking about is Autobahn?

Bottom line: lotsa different facors possibly at play here, and I'd be surprised if 1000 pound springs are the culprit...but could be wrong.

 

Veloce,

THanks for the feedback. Yes I am talking abotu Autobahn. It's by far the bumpiest track around.

I'm going to check the diff, but through the bumpy turns the car is really really stiff. When four seperate people come up and comment on the car's attitude compared to others through there, and I'm going into kidney failure due to the impacts, it makes me wonder. Alignment was set fairly aggressively to manage the sharper corners and camber verified with wear and temp indicators. Tried mid-range and lower softness settings. The softer the settings got, the more "porpoising" feeling I got, to where I felt like the spring energy was overcoming the ability of the shocks to dampen.

..and I headed down the wrong path here? When I have to do a full throttle lift for like 2 seconds to get the car to take a set, and when I'm getting into the ABS early because weight isn't shifting fast enough, sure feels too stiff to me.

Definitely open to suggestions as I've been racing/building early 911's for years and am climbing slowly up the cup learning curve.

 

Question: how much nitrogen pressures in the damper canisters?

 

180 psi

 

No you're not headed in the wrong direction. Softer springs combined with less bump will help manage the track's undulations. Also important is where your bars are set?

You could try 125 in the front cannisters keeping 180 in the rears. That's about where I usually run on our bumpy tracks....

 

JR I can certainly give that a try. I was under the impression that the pressure only impacted the sensitivity of the shocks rather than the overall performance.

Bars are set on 2 (soft) of 5 up front and 2 (soft) of 4 in rear.

 

I doubt the cannister pressures will solve your issues there but it it's a step in the right direction. There's so many variables in setting up a cup especially when dealing witha track surface that's less than perfect. We can all offer suggestions that may have helped with our particular experiences, but my best suggestion is to hire a good setup pro/driver and let them drive/setup the car.

That being said I'll bet you diff is toast and it's the most important part of your car's setup IMHO. You have to pull it to properly test it but it's worth knowing. Use Guards' replacement discs if it's gone....

 

JR,

Both are in the plan. Hoping I can Forest Gump something in the mean time. I'll do an inital test in the car in the diff and report back. If I find something easy enough to pull it and have GT redo. I have 3-4 weeks after my next event to get it done if needed.