Tire Pressure Question

[panameras]

Thanks Jim

You haven't answered my question. Obviously you can't improve the handling balance by just increase the tyre pressure but it will help and it might be most cost effective way to do so.

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? Also, don't worry about "too low a pressure can cause rim damage more easily" because in this scenario we are trying to increase tyre pressure not decrease.

Having said that, however, it won't hurt to increase the front tyre pressure a little over the factory recommendation to improve understeer (not eliminate) Hence my question again to those who have actually tried various front tyre pressures what do you think is the most ideal front tyre pressure over the factory recommended 29psi?

Originally Posted by MNBoxster

Hi,

Tire pressures are always measured COLD. You cannot eliminate or neutralize the Boxster's steering with Tire pressure alone, you can only make it more neutral. Alignmentspecs and perhaps even a change in some of the suspension hardware would be necessary to make it totally neutral.

I run a higher pressure than OEM spec as well, it gives the car better turn-in and it lowers the rolling resistance which aids acceleration and range (MPG).

But, there is no absolutely BEST Tire pressure. You need to take into account your driving conditions (consider Potholes, Freeway expansion joints, paved vs unpaved, etc.), your driving style, even the type of wheels you use (too low a pressure can cause rim damage more easily). It's best to experiment using an accurate Tire Gauge until you find a pressure that you think gives you the best ride and response...

Happy Motoring!... Jim'99

[Topless]

I have been running 35/35 cold for a while now and tire wear is very even across the tread. I do notice a little more (detail) up front on rough roads. These pressures have helped to preserve the outer shoulders on track days also.

Track hounds will tell you that maximum dry traction is achieved at the lowest pressure you can run without the sidewall beginning to roll over. This pressure varies greatly between drivers. Super smooth, very experienced drivers can run lower pressures than a guy who really tosses and slides his car around. A novice who does a lot of sliding can destroy a set of tires in one day with too low pressure.

[porschedude]

yeah, porsche recommends 29 psi front. but i use 31 psi front and 36 psi rear and I am happy with it. i think it is all based on personal preference and see how you like the handling.

[MNBoxster]

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?

Hi,

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

[unklekraker]

I was going to start a thread about tire pressure but thanks for the search forum tools
I can't believe that they put 45 all around on the tires that they just installed today on my car after reading this thread

So it's safe to say to go
225/40 18 Front 31psi
265/35 18 Rear 36psi