dt,
Probably the most important thing, even trumping your worries about speedo accuracy, performance, etc. is that for the electronic stuff in your drive-train and braking systems to work properly (
PSM, and more importantly ABS), you need to have the tire diameters match in two ways - they should to be within about 3% tolerance of the stock diameters, and they need to be within 3% tolerance of diameter front to back. The most important one is the front-to-back tolerance. Even though you manually turn off
PSM for the track or autocross, it's still lurking there, and if it senses a total dire emergency, it will activate. And, I don't think you want to go without ABS. What will happen is the computer will start throwing faults like crazy if you're out of spec, and the systems won't work correctly...
Go to tirerack.com and look at the spec for your stock tires... in the 'specs' section for each tire, they have the diameter of each tire size in inches and 10ths of inches. Do the same thing with the tires you're interested in, and do the math... if you're within that 3%, you'll probably be fine.
Believe it or not, many tires of the exact same size, say 265/35/18, but from different manufacturers, can have vastly different diameters.
brad
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PSM - Porsche Stability Management
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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. |
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Having fun in Puerto Rico
Linear Mode
