Hey Unregistered it seems that you haven't posted a message in our forums yet. Please join in on the fun and post a message! Click on Forum, then click the name of the appropriate forum such as "Cayman Chat" and then click the New Thread icon (looks like a Cayman door and side grill). Enter your message in the message editor and press submit and you are on your way!
Cayman CompetitionAuto Cross, Club Racing, DE, this is the place to discuss the Cayman on the track
Your Donation Will Be Used To Pay For our ever increasing bandwidth costs, our hosting Service, domain registration, software licensing fees, maintenance costs and product evaluations Only!
Please enter your donation amount above, and then click on the donate button below.
A simple or maybe not so simple question. Is the stock tire size stagger for 18" CS optimal for balanced handeling? Since the tires are the ultimate arbiter of traction, what is the best solution for maximum cornering power?
I've read many threads that seem to indicate that the car is set up to understeer from the factory for safety on the street. Is this a function of tire pressure / sway bar settings or is the car purposely under tired in the front?
If it is under tired in front would'nt it make sense to only increase the tire size in front to make the car more neutral & improve braking? ( DE Track use) It would also require less "tuning" with the sway bars as well.
it is not under-tired in the front at all. plenty of grip from 245's to steer the car. the understeer is primarily alignment, although spring and bar settings do play a part also.
If anything, it is under-tired in the rear. if you are doing track work, I would recommend 245 front and 295 rear. this is best done with 9" and 10" wheels. make sure that the overall tire diameters match front to rear.
A simple or maybe not so simple question. Is the stock tire size stagger for 18" CS optimal for balanced handeling? Since the tires are the ultimate arbiter of traction, what is the best solution for maximum cornering power? . . .
That's a pretty difficult question to answer - I think you would have to do some extensive testing (skidpad, slaloms, lap times) where the only variables are the tire sizes - in order to come up with an objective answer. That's pretty much out of the question for individual owners like us. One would think that Porsche would have done that during development - but who knows?
I have recently started running 245/275 on the track, and still tend towards oversteer; I would agree with joel-cs, I could probably use 285 or 295 on the rear. The problem is finding tires in those sizes that maintain close to the same diameters as OEM. Personally, I think the stock sizes are fine for handling on the street, where I don't expect to approach the handling limits of the car.
__________________
To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.
2006 CS Tip (Daily Driver & Part-time Track Toy)
2005 Ford Expedition (to haul the CS)
2006 Lexus RX400h (wifey's)
Gone, but not forgotten: 2002 WRX, 2004 MINI
diverdog: Finding the best solution for maximum cornering power would require testing a lot of wheel and tire size combinations on a skid pad. Then we'd still wonder about transitions, turn-in, etc. I haven't tried any other wheel or tire sizes yet, so I'm just guessing that inflating the front tires a few more psi and getting a more performance oriented alignment would help reduce the mild understeer noticably. That's all I've done, and the handling seems about neutral on track and at autocross.
Since the stock CS already has mild understeer, I don't think it needs wider rubber in the rear instead of the front. I may be wrong, but the RAC 9 and 10" wheels with 245 and 275 tires should provide well balanced handling and performance for our 300-hp mid-engined cars. My guess is that much more wheel and tire than that on the stock CS would start a curve of diminishing marginal utility where the extra unsprung rotating mass would eventually reduce overall performance. I don't even try to guess about the wheel/tire limits of a highly modified (engine, suspension, brakes, etc.) CS.
On the street stock tire sizes are fine. I drive very conservatively and only about 150 miles a week or so.
On the track with stock tires at 38F / 39R hot the car feels pretty neutral to me. It rotates nicely. I think maybe some AX seat time where I can safely push over the edge will be helpful.
I'm planning of modifying the car for DE's as I gain more seat time. I'd like to do it in a logical progression. Safety & durability items items first, then performance.
The car has PASM and I'm not planning on lowering it as I scrape on my driveway at stock height. Suspension mods I'm considering are lower control arms and adjustable bars & links F&R . Also an LSD.
I will be getting new wheels & R series tires for the car next year & would like to chose wisely.
Thanks for the helpful observations.
PASM - Porsche Active Suspension Management
This active damping system offers continuous adjustment of individual damping forces based on current road conditions and driving style.
The driver can choose from two setup modes, ‘Normal’ and ‘Sport’, using a separate ‘damper’ button on the center console. ‘Normal’ mode is designed for general road driving and circuits with uneven tarmac. ‘Sport’ mode is intended for smoother track surfaces, where the harder settings help eliminate pitch and roll.
In either mode, PASM continuously evaluates the current conditions while automatically selecting the corresponding damper rates from the respective set of mapped values.
A range of sensors are used to monitor the movement of the body under acceleration, braking and cornering maneuvers, as well as on poor road surfaces. The PASM control unit then evaluates this data and modifies the damping force on each individual wheel in accordance with the selected mode. The result is a significant reduction in body movement as well as a better grip on the road.
For example: if ‘Sport’ mode is selected, the suspension is automatically set to a harder damper rating. If the quality of the track surface falls below a certain threshold, the system immediately changes to a softer rating within the ‘Sport’ setup range. When the quality of the tarmac improves once more, PASM automatically returns to the original, harder rating.
Need more information about PASM? Click this link: FAQ for PASM
LSD - Limited Slip Differential
A limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.
The main advantage of a limited slip differential is found by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate freely– the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.
To see the installation of a TBD style unit Click Here
To see the installation of a LSD style unit Click Here -> Article Forthcoming Stay Tuned
I'd say someone who says the 245/275 combo gives enough tire in the rear should do some rough math. Weigh the car on scales (or look up someone elses weights). Go get a rough idea of how many square inches of contact patch your front and rear tires have. Then tell me how many more psi your rears see than the fronts on that combo.
It's considerably more. In fact, I'm pretty sure if you do that math again with 245/295, you'd find you don't really have quite enough rear tire. Now, that rough math is not the end-all-be-all of calculations, but it certainly gets you in the ball park.
Sure, I've got 400HP in mine, but 245/295 is still very easy to cause oversteer with.
My first post. Don't own CS. Starting to think about getting one.
A few years ago when driving Autocross and lapping events in a Boxster and Honda S2000, I had maximum front wheel camber and a toe adjustment. The result was the cars went from understeer to a much sharper turn in on corners, especially tight corners around the cones.
However, the adjusted toe does not allow the steering to return to neutral as one would normally expect. So, driving down the freeway the car could be a little darty if not paying attention.
BTW, the knowledge level on this board is very impressive.
Is that the most tire you can run without fender mods?
How much work to fit 275/315? or 275/335?
Yes, that's the most you can run without fender mods. How much work? Depends on how nice you want your new flares to look, I suppose. Would be nice if people would start racing these things so someone would make a set of removable rear fenders that were pre-flared. I'd love to get a 275/335 combo under there, but I'm not sure I'm ready to do that to the car. Yet.
With the right suspension setup i bet you could squeeze a 305 on the back. it would be a very tight fit and you would probably need very stiff springs to make it work. i am looking into it and will let you know what happens...
. . .Sure, I've got 400HP in mine, but 245/295 is still very easy to cause oversteer with.
--Donnie
Donnie:
What kind of tires are you running on the track and what hot pressures?
Andrew
__________________
To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.
2006 CS Tip (Daily Driver & Part-time Track Toy)
2005 Ford Expedition (to haul the CS)
2006 Lexus RX400h (wifey's)
Gone, but not forgotten: 2002 WRX, 2004 MINI
joel-cs, we already tried with 800 pound rear springs and you'll get rub. At the ride height I really want it's pretty easy to get rub with the 295's, in fact.
Andrew, my best experience right now is with PS2's during the One Lap. 40psi hot.
Until 
