iceD

So i reduced the PSI to 35. Not digging it, something doesnt feel right.

I think i will try 38

bob

Depends, if you really want to get down to it, most tire manufacturers provide inflation tables for their tires. You just have to cross reference the OE inflation pressure with the OE tire size then look up your current tire size and see if a change in pressure is needed.


Also the tire's contact patch is dictated by tire pressure x vehicle load. That is to say the size and shape of the contact patch is dictated by both the pressure in the tire and the dynamic load placed on the tire. As pressure is increased the contact patch can be reduced relative to the load placed on the tire.

El Coyote GT/CS

These statements seem valid to me. I've looked into changing tire sizes and how to determine the possible change in pressure and have come up with the following:

Assuming the the rim size is proper for the tire, observe the max load and max pressure printed on the tire - that should be considered 100% of the tire's capacity. Figure out what the actual load on the tire is when the car is loaded as driven (curb weight +). Remember there are 4 tires carrying the wright and consider any significant front to back weight distribution differences. Divide this "actual load" per tire by the max load to get the % difference, then multiply the max pressure by that % to get the required air pressure to carry the actual load. Adjust that pressure as needed for any temperature variations.

From there, you may have to drive around and mess with the pressure a little to dial them in for your type of driving. And watch the wear/scuff patterns as mentioned above.

I did the math for a few of my cars with OE tires and it was very close to what was on the door stickers.

iceD

nice information!

ace72ace

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Anyone can check and see if they qualify as a troll by checking off how many of the above traits match your own posts. Fun fact - 99% of internet trolls don't actually consider themselves one. The other 1% doesn't know what this definition means, so thanks to the original artist/comedy genius who provided this public service.

Black Fire

I personally have always kept my tires in the 32-35 psi area and I have always had even wear. And this goes for every tire of various sizes on all my previous performance cars.

iceD

i talked to a discount tire guy yesterday and he said he wouldnt go above 33 psi on this car.

I asked him if different sizes require different psi, he said NO, it doesnt matter.

I was like ummm ok. cool.

Right now im running at 36 psi.

bob

Sounds like a dumbed down answer, chances are your new tire size has a load rating equal to or higher than your previous tire size requiring no change in pressure. Tire size, load and speed ratings are important and dictate a great many things.


Here is something Bridgestone provided (albeit a bit dated);


http://www.tiresafety.com/images/Tir...t%20Manual.pdf


(toyo has similar information as well, unfortunately I couldn't dig up Michelin's tire manual and the RMA site wants to charge around 115 or 120 bucks for the same information.