Tire Pressure Question

[NickCats]

Sammy and I ran an autocross in Indiana yesterday and we both did really well. I forgot to let the air out of my tires for the way home ( about 90 miles ) and I must say I really liked the way the car felt with the increased tire pressure ( I think I had 36 psi in the front and 38 psi in the rear ). I dropped the pressure down to 29 / 36 once I got home, but I was wondering what would be the disadvantage of running with increased tire pressure ?

Pictures :

Sammy's Front



My Front



Sammy's Friend's Shifter Cart



Sammy's Rear



My Rear



Any input would be appreciated...

Thanks,

Nick

[edevlin]

I run 36 lbs front and 40 lbs rear all the time with my 18" PS2's and I dont track my car, just for road use. I think I got that redommendation from someone on the fourm a while ago.

Any lower pressure than that and the sidewalls feel too flexible on hard cornering. Having gone through a pair of PS2's running the tires at that pressure, I found no unusual wear patterns, just the usual wear on the inner edge of the tire from the allingment setup.

Ed

[NickCats]

Thanks for the response, edevlin !

I found some good threads on the subject :

http://986forum.com/forums/showthread.php?t=7355

http://986forum.com/forums/showthread.php?t=5353

I am still confused, though

If Porsche recommends 29 / 36 , and you run 4 to 7 psi above that yet you do not experience any unusual tire wear, are there any other issues to be concerned with ?

Nick

[racer_d]

Part of the result of running the factory 29/36 is increased UNDERSTEER. By running more air in the front, you reduce the understeer tendancy. While running pressures too high may cause a change in tread life, you may find the benefits outweigh the drawbacks.

[panameras]

Originally Posted by racer_d

Part of the result of running the factory 29/36 is increased UNDERSTEER. By running more air in the front, you reduce the understeer tendancy. While running pressures too high may cause a change in tread life, you may find the benefits outweigh the drawbacks.

The factory 29/36psi recommendation is that hot or cold?

Your point does makes sense, understeer is always safer for an average driver. How many more psi do you actually put in the front tyres to reduce understeer or whats the ideal front tyre pressure to have a neutrally balanced boxster?

[MNBoxster]

Originally Posted by panameras

The factory 29/36psi recommendation is that hot or cold?

Your point does makes sense, understeer is always safer for an average driver. How many more psi do you actually put in the front tyres to reduce understeer or whats the ideal front tyre pressure to have a neutrally balanced boxster?

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