I have 285/30/20 rear and 245/35/20 front rims. when i got them they had 45psi rear, and 40psi front. what tire pressure would be good to have?

 

thats way to high...at work 40+ is how much we put on trucks...tire size doesnt reallly affect how much air you should put in...i think what the little sticker when you open your door says is 32 all around...but i run 35 all around...

 

Yup, start with the OEM pressures (35psi) and adjust accordingly. You shouldn't need to go more than ±3 to 4 psi to get a good ride & handling feel from them.

 

Good ride? He has 20 inch rims with a 30 aspect ratio in the rear. How good a ride is that ever going to have? He may be able to get it to handle well, but I bet he has a lot of understeer.

 

As good as can be expected I can imagine at 40 to 45 psi they had to be feeling like solid rubber. Yeah, 245/285 is pretty extreme - personally, I love the 255/285 combo.

 

Tire pressure is stated on the placard. Think it is on the drivers door frame.

 

Aftermarket tires do not necessarily require OE placcard pressure. It depends on the load rating and size of the new tires.

Check this thread where myself (Bridgestone engineer) and a Falken engineer (if I remember right) already informed davidv and the other guy above of the correct way to find your pressures:

https://my350z.com/forum/wheels-and-...ket-tires.html

I'm not sure why they choose to ignore the advice of tire experts (they are obviously smarter??), but basically, use the guide at this link to determine optimal pressure. Let me know if you need any help. Tables start on page 28.

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

 

just knew it was a matter of time before we got the self proclaimed tire "expert" chiming in with some confusing formula used in some laboratory.

do what Dave said; stick 35 psi in it and call it a day. or you can take advice from a person that designs crappy tires. your choice