Here is a great link for a wheel offset calculator that compares the effects of wheel spacers or wheel changes from one setup vs. the other.
Please note that the offset varies on many of the factory option wheels therefore the same spacers will yield different results depending on the wheel in use; this info is available in the Porsche Tequipment Cayman S catalog.
Wheel Offset Calculator
I hope it is helpful to you. Joe
Maybe you should but that in the "Files" section for future reference.
There is also another useful tool here:
http://www.planet-9.com/cayman-tires-wheels/11544-freeware-great-tire-size-calculator.html
Hello Santa Fe,
That is a good idea but I,m sorry to say that I'm not familiar with the required procedure. Would somebody please move it to files for me?
Thank you,
Joe
The calculator doesn't tell you what kind of spacers you are supposed to need.
I am looking at track tires for my Cayman. The Michelin Sport Cups don't come in stock sizes. What size do most people buy? I do not intend to buy Sport Cups, but this is important because I am considering the Yokohama Advan A048 or the BFGoodrich g-force R1s, which also don't come in stock Cayman sizes. Stock Sport Pilots are 25.4" diameter, tread 9.5", for the front and 26.3" diameter, tread 10.7", rear. The Yoko is not strictly R-compound, but a compromise compound, so I will probably chose that tire as a first high performance track tire. The very new BFG g-force R1 is supposed to be much better than Hoosiers, cheaper and last longer, according to Tire Rack and reviews.
With the Yokos, I might get 235/40-ZR18, 25.4" same diameter as stock, 9.6" tread, and 265/35-ZR18, 25.2" diameter while stock is 26.3", 10.7" tread (stock) diameter. With the BFG g-force R1 tires, I might either go with 225/40-ZR18 (9.3" wide versus 9.5" for stock) on the front and 265/35-ZR18 (10.7", same as stock) and both have 25" diameter, or 245/40-ZR18 (9.8" wide versus 9.5 stock) and 275/35-ZR18 (10.9" wide versus 10.7" stock), both 25.4" diameter. If I go wider than stock Sport Pilots, I would rather have the same fractional increase front and rear which the last g-force does, but I need to check out fender restrictions. I can't do this with the Yokohama Advan A048 tires since the rear is stock width and the front is 0.2" narrower. I don't worry about the diameter so much since I the speedometer is not used on the track, but I wonder why the stock tires have a diameter nearly an inch larger than the fronts.
Does anyone have any insight of tract tire sizes?
Charles
If you don't want MPSC, I suggest Toyo RA1 in
F: 245/40x18 & R: 275/35x18. They'll work fine w/o any ABS/PSM problems. I'd stay away from the BFG R1 unless you'll be trailering your car or have control over the Midwest's unpredictable weather. Although very sticky, they are essentially street legal slicks which are not usable in the wet, even for your short drive to GIR.
That said, I'd think twice before moving to Rs given your limited track time. Here's a
good read
which I think describes the comparisons between street, R compound, & slicks well. In short, if your desire is to be faster, concentrate on improving driving skills. Even with slicks on your modded CS, you'll still be slower than several of the experienced drivers were they in a stock, 2.7l Cayman & PS2s. That's the reality of the track. You're not yet at the level where you're as fast as you can be on street tires. Until you can lap consistently & are being limited by your street tires rather than driver skill, I'd stay off Rs. Just my $.02.
Thanks for the advice Dan that one should work up to track tires slowly. I will wait awhile for the f-force R1s. In the meantime, I think I will go for the Yokohama ADVAN A048s with 235/40-ZR18 in the front and 165/35-ZR18 in the rear. They seem better rated than MSPC and last longer with tread that is works on wet roads/tracks, but probably not as well as MSPC.
I am thinking of a ways to transport track tires to the track, short of trailering my car. I think the roof rack will hold 3 and the front trunk 1 - that's one way. Another is to build a SIMPLE trailer - four tires on a pole longways with small trailer wheels on the pole at the mid-point. There will be little net weight on the "hitch" which might be attached behind the bumper extensions so not much rigidity would be needed (unless someone rear-ends you). If you can see the tail lights around the tires, I doubt if lights would be needed and one-wheel or attached trailers require no licenses, so one might have a case here too, especially if you attach a red flag to the end - if stopped, get a tag.
