Lt235/75/15
 

I currently have LT235 75 15's on my blazer. I was told the other day that you must incress your tire pressure when its really cold out. Its been around 15 degrees. I have about 32 psi's in them right now, they had said that it shouuld be doubled in cold weather. I thought they were crazy. Is this really true, and if so is 64psi too much.

I don't know who told you that, but they're crazy. 64psi is too much for a tire.
I keep my tires around 40-45 unless I'm off roading.

So does it matter for cold weather?

Yep, don't use that original source for tire pressure advice. :)
The idea is to check and set the pressure when the tires are cold, so leaving them at 32psi when it's 15* is fine. As the temp rises or as you drive, the pressure will increase within a safe limit.

BTW - 32 is a reasonable (and factory recommended) PSI. I always like to have a bit extra in my tires though.

NEVER exceed the pressure rating on the side of the tire! As far as cold weather is concerned, just maintain manufacturer recommended specs and you will be fine. You should check your tire pressure at least once a month anyway.

i nitrogen fill mine and they stay at 35 psi

Figured someone would bring up nitrogen... I'll just link to the more recent thread instead of dragging this one off topic --> Nitrogen filled tyres.

My air filled tires stay at the pressure I set them at as well. It doesn't matter what you use, you should still check your pressures. Any tire can leak.

like Kyle said, that'd be a no-no. unless you're running LT's, 98% of the passenger tires are maxed out @ 35 psi. there are some "P" tires that max out @ 40 to 44 psi.

most people don't run LT's on their trucks, and other than you guys running 31's (and bigger), i think i'm the only one (that i know of) that runs LT tires.