cup spring rate
08-23-2007, 04:56 PM
#2
Addict
Rennlist Member
Rennlist Member
Hey Sten,
How specific did you need to be? If you want to race your car as a Cupcar, you may be required by the organizers to install original Factory parts along with a number of other modifications. But the short answer is 600/800 lbs front and rear.
Here's a bit more detail:
How specific did you need to be? If you want to race your car as a Cupcar, you may be required by the organizers to install original Factory parts along with a number of other modifications. But the short answer is 600/800 lbs front and rear.
Here's a bit more detail:
For the Racing Carrera Cup conversion the only modifications were to exchange the following parts to:
Stiffer rubber front stabilizer bar bushings
Stiffer rubber Cup/RSR specific front steering arm rubber couplings rather than RS' C4 units
Front and rear monotube Bilstein shocks
200-600 pound progressive rate front springs and 240-800 pound progressive rear springs.
Rear trailing arm plates inverted for more negative camber
Modified monoball upper spring mounts. These are of the older, unsealed Carrera Cup design rather than the later sealed RSR type used on the RS. Also, the front racing mount moves the strut into a position of more negative camber than the RS mount does.
Stiffer rubber front stabilizer bar bushings
Stiffer rubber Cup/RSR specific front steering arm rubber couplings rather than RS' C4 units
Front and rear monotube Bilstein shocks
200-600 pound progressive rate front springs and 240-800 pound progressive rear springs.
Rear trailing arm plates inverted for more negative camber
Modified monoball upper spring mounts. These are of the older, unsealed Carrera Cup design rather than the later sealed RSR type used on the RS. Also, the front racing mount moves the strut into a position of more negative camber than the RS mount does.
08-23-2007, 06:12 PM
#5
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Rennlist Member
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Sten 
Dave,
The info is from page 8 of that massive 964 Cup thread from February. You remember it, right?
https://rennlist.com/forums/showthre...ghlight=cupcar
Dave,
The info is from page 8 of that massive 964 Cup thread from February. You remember it, right?
https://rennlist.com/forums/showthre...ghlight=cupcar
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08-24-2007, 08:40 AM
#8
Nordschleife Master
The 200-600#f 240-800#r progressives is correct. They are NLA from Porsche, and darn hard to find used. For used ones, you'd have better luck in europe. Only the stock springs are legal in PCA GTC1...linear 600/800 springs are not.
08-24-2007, 09:44 AM
#9
Nordschleife Master
"Geoffrey, Please chime in."
The information is correct and the link to the larger thread should give you most of the detailed information. There is a proposal into PCA Club Racing to look at alternative springs for the GTC-1 class. I bought all of the springs last year from Weissach, so Colin is correct when he says they are NLA.
The information is correct and the link to the larger thread should give you most of the detailed information. There is a proposal into PCA Club Racing to look at alternative springs for the GTC-1 class. I bought all of the springs last year from Weissach, so Colin is correct when he says they are NLA.
08-25-2007, 09:45 AM
#11
Nordschleife Master
It has been my experience with the C2 that the spring rate split between the front and rear is not as wide as the earlier tubs. I would start with a spring rate of 700/800 or 800/900 Front/Rear, but you'll need adjustable bars like the RS or TRG bars. I am finding that I prefer a softer spring rate and a stiffer sway bar than a stiff spring. It makes the car more compliant. Since you have Ohlins, you should be able to adjust the car for proper weight transfer. I think that if you go with 600/800 linear spring rate, you may find you have oversteer you can't dial out properly.
08-25-2007, 10:50 AM
#12
Rennlist Member
It has been my experience with the C2 that the spring rate split between the front and rear is not as wide as the earlier tubs. I would start with a spring rate of 700/800 or 800/900 Front/Rear, but you'll need adjustable bars like the RS or TRG bars. I am finding that I prefer a softer spring rate and a stiffer sway bar than a stiff spring. It makes the car more compliant. Since you have Ohlins, you should be able to adjust the car for proper weight transfer. I think that if you go with 600/800 linear spring rate, you may find you have oversteer you can't dial out properly.
I have read that the 997 Cups have matching springs or they are damn close.
08-25-2007, 11:51 AM
#13
Nordschleife Master
Think about why you would want the lighter end of the car to have heavier springs...It has been my experience that the C2 likes spring rates almost the same front to rear, with the rear using a little more spring rate. I've driven a car setup with 900front and 800rear springs and didn't like the handling. We've since gone back to a more traditional setup and the car has been much better.
08-25-2007, 12:18 PM
#14
Rennlist Member
Hi Geoffrey,
Actually the story is closer to me being pissed about the constant oversteer after spending $$$$ and trying everything, I dropped my car off and said “fix it”. They took at what seemed at the time as a drastic measure….swapping the springs to TRY to induce understeer. It worked at VIR I had too much US but my times dropped another second. For some reason that weekend I was unwilling to move the rear sway to full hard, so at the next event I tried that at WG and loved it. We also increased the front camber for WG which probably helped.
Actually, the event that prompted the swing swap was a DE at Mid-O and after speaking to one of the mechanics for AT Speed they said that they run inverted springs on their 997 Cups AND more nitrogen in the front (I am sticking w/ 200/200). Also, I found this thread where Kinetic (pro driver Nic Jonnson) recommends the inversion: https://rennlist.com/forums/996-gt2-gt3-forum/345403-996-gt2-moton-track-setup-suspension.html , at least on 996 GT3s.
With that being said I realize that the 997 and 996 platforms might react differently to this even though the weight distribution might be similar. Either way, I appreciate you input and will probably try slightly heavier springs in the rear next time the shocks come off the car….which hopefully will be a while.
Thanks,
Jim
P.S. I am quite sure the OS problem made me a much better driver over the last year as I gained even more confidence….when the back end is constantly letting go, you get used to it after a while. Another unintended consequence is that with the constant fiddling/adjusting with the suspension I have learned a great deal over the last year, but with a LONG way to go.
Actually the story is closer to me being pissed about the constant oversteer after spending $$$$ and trying everything, I dropped my car off and said “fix it”. They took at what seemed at the time as a drastic measure….swapping the springs to TRY to induce understeer. It worked at VIR I had too much US but my times dropped another second. For some reason that weekend I was unwilling to move the rear sway to full hard, so at the next event I tried that at WG and loved it. We also increased the front camber for WG which probably helped.
Actually, the event that prompted the swing swap was a DE at Mid-O and after speaking to one of the mechanics for AT Speed they said that they run inverted springs on their 997 Cups AND more nitrogen in the front (I am sticking w/ 200/200). Also, I found this thread where Kinetic (pro driver Nic Jonnson) recommends the inversion: https://rennlist.com/forums/996-gt2-gt3-forum/345403-996-gt2-moton-track-setup-suspension.html , at least on 996 GT3s.
With that being said I realize that the 997 and 996 platforms might react differently to this even though the weight distribution might be similar. Either way, I appreciate you input and will probably try slightly heavier springs in the rear next time the shocks come off the car….which hopefully will be a while.
Thanks,
Jim
P.S. I am quite sure the OS problem made me a much better driver over the last year as I gained even more confidence….when the back end is constantly letting go, you get used to it after a while. Another unintended consequence is that with the constant fiddling/adjusting with the suspension I have learned a great deal over the last year, but with a LONG way to go.
08-25-2007, 07:55 PM
#15
