dshulik

After having four Bridgestone Potenzas worn to the threads in about 24 months having driven the car very conservatively (relative to some of you out there), I realized there was a huge allignment issue. From the onset of tire wear I tried having the car realligned, but hadn't come across Rennlist in time to cure it properly. The allignment problem was finally resolved by my new mechanic's knowledge from having worked as a mechanic at Beverly Hills Porsche. I realized he knew his stuff after his comments about proper allignment methods matched what I've read on this site (a little too late for my tires and checkbook)

I just replaced the tires with more of the same. I again went with Bridgestone Potenza RE730s. So then let me get to the point: I run Porsche Turbo Twist style with 225/40/18 up front and 265/35/18 in the rear. I've been offered to borrow my mechanic's nifty little heat sensor thingy he uses at the track for his factory 993 RSR clients among others so that I can judge if I'm overinflating or underinflating based upon the temp on inner/outter tread area. Anyone who could save me the hassle of jumping in/out of the car after freeway runs to heat the tires and check temp would be greatly appreciated. My tires and checkbook will thank you...well maybe just my tires, the checkbook is a little light right now.

Any tire gurus out there?

Ell

Piromitor (not sure of the spelling) is what you have to check the tire temps.
The best thing to do is to just go to an empty parking lot and drive around in a circle and keep getting tighter until you start to hear the tires skid. At this time check the tire temps. If the tire is hotter in the center then let out air, hotter on the outside add air. Check the tire temps on the outside tires then change direction. Repeat this proccess at least twice to fine tune your pressure.

Following this you will find that you will be able to take the turns tighter with out loosing grip. This should only take you about 30 minutes and the benifits will last you a long time. It would work best if you have an air bottle on hand to make adjustments. That night or next morning check you air pressure and record them. That will be your cold tire pressure. Depending on the level of stress you place on the tires, the temps will change alot, = or - >6lbs. I have incressed my pressure by 10 lbs driving hard in a autocross event.

I had a friend help me with this at a race event and was able to cut five seconds from my times. Setting these tires in this manner will really make your day.

I run the Potenza 730 tires 16" and I run hot at 44lbs in the front and 39 in the rear. I have ran my tires all summer racing and daily driving and have burned off half of the treads. I have evan wear. Your temps might be different.

Good luck
Ell <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

urnotthesameina928

With 225/40/18 up front and 265/35/18 in the rear you are running on a low profile set of tires. You should be using a good tire gauage (dial gauge style)easy to read and more accurate than a pencil style gauge. JC whittney is a good source. Run the tires somewhere near their recommended max pressure. Pressure should always be checked when the tires are cold and at least monthly. Under normal tire operation, approximately 1psi of tire pressure will escape every month. Also, for every 10 degrees F change in ambient temperature, tire pressure will change by approximately 1psi.
Check your owners manual for what porsche recommends and note that the higher the speeds you would drive your car would suggest a higher pressure on the tire...up to its max rating.. I would not go below 8psi of the max pressure rating of the tire since these are very low profile tires.. Dave.

dshulik

Thanks for the replies. Wheel Enhancement in Culver City who sold me the wheels orginally specialize in Porsche wheels and have some experience with 928s albeit not that frequently. They suggested going 4 or 5 psi below the specs in my manual for the rear tires while running the fronts at spec. They said this is due to a tendency for the center of the rear tires to wear more quickly on the 928. I'm not sure the specs hold true for a larger, wider, lower profile wheel/tire setup. Since this car is a daily driver but I do roll in excess of 85mph on the freeway to and from work and I also push it through some high speed twisties along the way once off the highway (@70mph)I think having correct pressure to handle high speed is crucial for safety as well as longevity of the tires. The manual suggests around 35psi if I recall correctly, and the tires are rated up to 45psi max. I've been running 36psi for the three days I've had the new rubber. I may do the temp testing approach, but not sure where to begin since I don't have a portable air pump. (AAA will have to save the day in the event of a flatting I'm afraid) Any suggested benchmark on psi's to begin with?