kevs

I just got my 65K minor service today and my mechanic said that my 245/40/18 tires (18x8 SSR GT1) only needed to have 33psi for air.

I remember a thread awhile back I wrote that someone said I should subtract 8 from the max. pressure of low profile tires and that should be the recommended pressure.

My max. pressure is at 51psi, so I had it at 44psi (even though that 7 less, not 8) cold. I went to a gas station and checked my air and they weren't all consistent (38psi, 39psi, 40psi, 38psi), so I put them all to 45psi warm. I'm thinking it'll go down to 42psi(?) cold.

Where should my tire pressure be at?

Thanks in advance.

bravo261

iTrader: (1)

38psi cold is good

SCRUFFDOGG

i run my 245/45/18 in my truck at 40 psi cold

Brandon@TR

This is an excellent question and one that I get all the time. If you have done the upsize correctly the tire should have the same internal volume as your OE size. Because it has the same volume it should have the same pressure as listed on the door jam of your car. Please check out the following link for a complete discussion. Your mechanic was probably right, but I don't know what car it is so I can't say for sure. That said I run mine at 36 PSI. That's a couple PSI more then spec...

http://www.tirerack.com/a.jsp?a=DZ1&...l/pressure.htm

kevs

Thanks for the input, everyone. Yeah, I think I'm running a little high right now. I'm around 42psi cold going into 46-47psi warm. My gas mileage isn't doing so well either because of it (I think).

With this weather change, things are getting funky. I'm trying to catch my tires at a time when it's cool enough so that I'm getting true cold air pressure but warm enough to not throw off my measurements.

I'll put it back down to 36psi cold in the morning.

kevs

A thought just occured to me...why not have people run "warm" tire pressure readings because our tires will automatically expand after driving even 2 miles.

With cold pressure, it's too hard to gauge when winter mornings elicit 35-degree weather and summer mornings give off 72-degree weather.

Either season, the tires would still warm up the same, wouldn't they? Isn't tire pressure during driving what's most important?

That said, I'm running at 45psi warm after driving 10 miles.

By the way, I'm driving a 1998 GS400 on 18 x 8 SSR GT-1's 245/40/18 with TEIN HA's dropped about 1.5".

Any thoughts?

Wald GS

iTrader: (1)

I have 245/35's and 295/35's. I have them at 39 PSI cold.