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Cayman Tires & WheelsDiscussion of Tires, Wheels, Suspension, etc.
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I'm enjoying my first Porsche (Cayman, non-'S'). Winter is fast approaching and I'm hitting a brick wall when searching for a winter tire for the stock 17" rims OTHER than the Conti's offered by my local Porsche dealer. Anyone know of compatible dimensions I can use for these rims? I want to outfit 'em with some good winter tires and buy 19" summer rim+tires in a few months.
You can up size: 255/45-17 are close extremely close to the 235/50-17 when it comes circumference (however it is wider you will have to check and see if the width is problem for the rim). The Dunlop WinterSport M3's are available in that size. If you up size the fronts to 225/50-17 there are lots of choices. It seems the rear will be limiting factor. There is 245 Pirelli 210 SnowSport that come in the 225 front also.
I just bought the Conti TS810 S in the 18" sizes for my CS. I have not had a chance to drive in the snow yet but I did drive in lots of rain in temps in the mid to low 30's and was very impressed with the grip and handling. Good luck in your search.
I have a few suggestions, but you should keep in mind that yesterday it was 83 F here, so my discussion of snow and ice tires is purely theoretical. Looking at the survey of thousands of responses at TireRack:
The highest rated winter tire is the Dunlop SP Winter Sport 3D. In a width staggered setup, you could run 205/50 front and 225/50 rear. This has correct front/rear circumference stagger, but is smaller than stock, so the car will ride ½” lower, and the speedometer will be off (high) by about 3%. You could also try 225/50 front and 225/55 rear. This puts the car 1/4'” higher, and the speedo reads slow by about 2%.
The Cayman systems (ABS, PSM) expect the rear tire circumference to be about 2” more than the front tires, and it is important to maintain this circumference stagger (as opposed to width stagger) when changing out tires and wheels.
Next most popular, Michelin Alpin and Bridgestone Blizzak , 205/50 front and 245/45 rear works, speedo 3% high.
As always, check with Jim@tirerack since they are the real experts. Also, since everyone in the cold places is looking for alternatives, please post back with whatever you do….
PSM - Porsche Stability Management
While it can’t overcome the laws of physics, the revolutionary Porsche Stability Management (PSM) system does lend an added degree of balance and control to the Cayman’s mid-engine driving dynamics, inspiring surefooted confidence in corners and extreme situations.
A standard feature on the Cayman and Cayman S, PSM continuously monitors steering input, road speed, yaw velocity and lateral acceleration to calculate the actual direction of travel. If the car begins to steer off line, PSM instantly intervenes with precision brake inputs on individual wheels to help bring the car back onto the driver’s intended path.
If braking alone isn’t enough to correct the vehicle’s cornering line, PSM then calls on the Cayman’s engine management system, adjusting engine output as needed to help stabilize handling. PSM can also compensate in an instant for mid-corner changes in load resulting from deceleration or braking. When Sport mode is selected with the optional Sport Chrono Package, PSM’s threshold for intervention is raised, allowing for greater driver involvement. If you prefer driving without automatic PSM assistance, the system can be set to standby at any time. In this case, it will only intervene under heavy braking, where both front wheels exceed the ABS threshold.
For all of its technical ability, PSM goes virtually unnoticed in everyday driving situations, preserving the Cayman’s natural agility.
__________________
....its even SAFETY YELLOW! What could be more practical???
The actual difference in circumference between the front and the back is less than 1" for both the 18" and 19" wheels. I have run the NT-01 that have exactly the same circumference, front and back, without any problems what so ever.
I believe that while the diameter (distance across the circle) of the 17”, 18” and 19” factory wheel setups vary by less than 1”, the circumference (distance around the circle) difference is 1.2” for the 17” wheel, 2.9” for the 18” wheel, and 2.6” for the 19” wheel. (As calculated here: Tire Size Calculator - tire & wheel plus sizing )
This difference is increased slightly (.16”) by the specified inflation difference front to rear, so the circumference stagger range from the factory is 1.36” to 3.06”.
Tires roll nicely no matter what size they are, so as long as all the tires are rolling, any size will do. It is when the tires are sliding, and ABS and/or PSM are working to save you that the factory specs matter. The onboard computer will calculate which wheel, and how much braking force to apply, based on the car’s design specifications.
The system has to be forgiving, since people may inflate the tires incorrectly, so it will not just stop working if the wheel circumference is wrong; it will just not do as well as it could.
On snow, and especially on ice, managing the skidding tire’s rotation is critical (and the reason for putting on winter tires), so I suggest trying hard to maintain the front/rear circumference stagger.
For high performance driving (DE, AX, racing), when PSM is often turned off, the tire size is less important, because at the limits of performance, sliding is a common thing, and it is the driver’s job to control it.
PSM - Porsche Stability Management
While it can’t overcome the laws of physics, the revolutionary Porsche Stability Management (PSM) system does lend an added degree of balance and control to the Cayman’s mid-engine driving dynamics, inspiring surefooted confidence in corners and extreme situations.
A standard feature on the Cayman and Cayman S, PSM continuously monitors steering input, road speed, yaw velocity and lateral acceleration to calculate the actual direction of travel. If the car begins to steer off line, PSM instantly intervenes with precision brake inputs on individual wheels to help bring the car back onto the driver’s intended path.
If braking alone isn’t enough to correct the vehicle’s cornering line, PSM then calls on the Cayman’s engine management system, adjusting engine output as needed to help stabilize handling. PSM can also compensate in an instant for mid-corner changes in load resulting from deceleration or braking. When Sport mode is selected with the optional Sport Chrono Package, PSM’s threshold for intervention is raised, allowing for greater driver involvement. If you prefer driving without automatic PSM assistance, the system can be set to standby at any time. In this case, it will only intervene under heavy braking, where both front wheels exceed the ABS threshold.
For all of its technical ability, PSM goes virtually unnoticed in everyday driving situations, preserving the Cayman’s natural agility.
__________________
....its even SAFETY YELLOW! What could be more practical???
There aren't many choices aside from Conti for the 17". You can get Pirelli's at Tire Rack.
Tire Rack
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