eclou

B

I want to explain a very simple principle to you. Maximum tire performance and maximum tire life is achieved when the tire has a maximum contact area with the road. They are not mutually exclusive.

Tires have the most grip when there is maximum contact patch. I think you understand this point.

Tires have the most life when there is maximum contact patch. This is because the wear can be spread evenly and over the most area. Just like 10 guys carrying a casket will fatigue less than 4 guys carrying the same casket.

Maximum fuel economy occurs when the tire has the least amount of rolling resistance. This occurs when the tire is inflated to its maximum pressure. This is because the tire no longer has a flat contact spot against the road, and it is more spherical in shape. Less contact area equals less friction and less resistance to rolling. Roll the bowling ball vs the water ballon. The bowling ball rolls effortlessly.

Comfort is improved when the tire has less inflation pressure and can absorb more shock and impact. The tire acts as a damper. The bowling ball absorbs no shock, the water ballon absorbs plenty.

So, max performance and life are the same. Economy is with higher pressures, comfort is with lower pressures.

B-Line

Yes, this is what I have been saying. Mutually exclusive can not be obtained with comfort and performance.
I agree with you. So, the correct tire pressure is subjective. Do you want performance or comfort?

And back to my original statement, recommended tire pressure is usually listed more for comfort than performance. That's why you can bump your tires up to 45PSI.. You increase perfromance, you increase longetivity but you give up comfort...

Ok, enough of this. Truth be told, neither you nor I are tire experts. We can simply restate what other people have told us, whom we respect. But we obviously both have track and racing experience and different opinions...

I don't need you to tell me what a tire is, how it works, etc. And you don't need me to tell you what PSI I think you should run the car. My entire point is, it's still somewhat subjective depending on use.

Nuff said.
B

eclou

B

The tire manufacturer cannot know all the different cars the tires are going to be used for. They stamp the tires for max pressure meaning beyond that the tire will fail/rupture. The same tire same brand same size will go onto many different cars of different sizes and weights/loads. A 225/45/17 tire at 45psi on a 2500 lb Elise will not have the same contact patch as on a 4500lb 545i. On the Elise, it will be overinflated. On the sedan 45psi might be ideal. Different cars with the same tire have a different ideal psi. Max psi cannot be viewed as a guide for anything other than safety.

texas911

So I've been driving around with the lower pressure and its made a huge difference in ride! Still feels very confident but when I go over a bump, there isn't that jarring jolt anymore, especially from the rear. Dare I say, its very supple for a sports car. Could be the cheapo Bridgestone tires too. So far very satisfied with the Turbo. I know the GT3/GT3RS is the current glamour boy of the Porsche line, but until Porsche gives us the option for a rear seat in those models, I'm sticking with the Turbo. Afterall, I'm raising two future Porsche customers!