texasgooner

Hi All,
I have Bridgestone SO3's with 225/45x17 on the front and 255/40-17 on the rear of my Carrera 3.2. Can anyone tell me the best pressure to have them? I don't drive like a lunatic also.
Cheers,
Justin

Kevin Baker

I'll check when I go to work and try to post back quickly

Matt H

Check the manufacturers sticker. Pressure recommendation are by vehicle and not by tire manufacturer. A common misconception.
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texasgooner

But my car originally came with either 15 or 16 inch tires. Now I have 17 inch cups on my 3.2 carrera. What do I do?
cheers

Matt H

It goes by load and inflation tables in that instance. I am swamped right now but I will look up minimums in the morning for you. You go from there as to what feels good to you. Do you know the vehicle weight?
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Viken

Since these sizes were not available for your car, you need to experiment with pressures. You should probably start high and go down if you feel you have too much. How about trying 34/38? My feeling is your car should feel right in the low to mid 30's, however.

Matt H

There are minimum pressures by load. You will need to experiment but there are actual min. pressure numbers. At 26 psi the 255 can carry 1132 lbs. per tire (I dont know the weight of the car) and the 225 can carry 1014lbs. at the same pressure.

Therefore, you know that you should be able to run the tires at a minumum of 26 psi (I am assuming it weighs less than 4 thousand pounds!). From there Viken is right, play with them, I defer to his 911 knowledge on the recommendation.
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texasgooner

I just want to know the pressures so I don't have uneven tire wear
cheers

jetskied

Your car is lighter than the newer cars. I have a 78 turbo which is a little heavier than you car. I run 18s with 28lbs in the front and 34lbs in the rear. At an auto cross I use 32 and 38.

texasgooner

I find it unbelievable there is such a wide range of pressures used with this car!

Viken

Well, there is no set formula to figure out tire presssures. Different weights, suspension tuning, rubber compounds, etc... All those make a difference in tire pressures. That's why it is mostly trial and error. If you don't feel comfortable with that, you should go back to the factory specified tires and pressures.

Matt H

Wow, I agree with Viken (sorry V, had to throw that in there!)
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Viken

Not that there's anything wrong with that. Is there?

Matt H

Nothing wrong with it, just doesnt seem to happen often. Have you tried the new PS2? I seem to remember you saying you were going to give it a shot.
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Viken

Well, yes. They are OEM on my GT3. Really great tire, both dry and wet. But, the sidewall is a bit too soft, and that sorta gives an uneasy feeling one needs to get used to.