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Old 09-11-2007, 07:56 AM   #12
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Join Date: Sep 2005
Location: Minneapolis/St. Paul, Minnesota, USA
Posts: 3,308
Originally Posted by panameras
...As for taking driving conditions into consideration, Porsche obviously has done the homework for you already. They only have one recommendation for most continents and mostl driving conditions for standard size summer tyres which is 29psi at the front. In other words this is the most ideal tyre pressure for most driving condition regardless Potholes, Freeway expansion joints, paved vs unpaved, etc. So if Porsche didn't worry about using different pressures in different conditions why would you worry?

I think you have to take a second look at Porsche's objective here. Their recommended Tire Pressures (as are the Tire Pressure recommendations from virtually all manufacturers) are derived as a compomise to best achieve several competing objectives such as Safety, Ride Quality, Performance, Reliability, and Range (MPG). As such, it is not the best pressure for actually fully achieving any one of them.

This is why your particular road conditions, Driving Style and Driving abilities can often be better served by adjusting the pressures to closer achieve what your individual objectives may be.

Not everyone who owns this car is Tracking it, carving out the Twistys, or bouncing off the Rev Limiter. In fact, given the Boxsters Original Buyer's demographic - established Business Person (probably a little older), second car, Leasee, etc., I suspect that at least 50% of their Original owners have never Tracked the car and probably drive it mostly for commutes and personal (rather than Performance) driving. For these people, the OEM spec Tire Pressures work just fine. But for someone who's skill is greater, or whose objectives are different, deviating from OEM spec gives them what they are looking for.

So far as Front pressures are concerned, I personally find that with my Pirelli P-Zero Rossos, on 18" Turbo wheels, 32 PSI gives me the best response while still preserving some modicum of Ride Quality. Those times I have Auto-X'd it, I've gone as low as 27 PSI, tried 26 PSI and the response seemed too sluggish. On the Track, 26 PSI might actually be OK, but the radii on Auto-X curves/turns tends to be much tighter than the Track...

Happy Motoring!... Jim'99

Last edited by MNBoxster; 09-11-2007 at 08:05 AM.
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