How much tire pressure and grill block question
 

Ok I have a 2006 chevrolet optra and the tires are rated at 44psi I have them at 50 how do I tell the strength of the side wall to over inflate them and improve economy? I'm also wondering if I should inflate the tires cold (I have a pump strong enough to do it) or hot? Due to the fact that as air rises in tem so dose the presure. I'm hoping to build a gril block for the winter to help the engin warm up.

a grill block is a good idea to warm the car up quickly, unfortunately it wont help warm the tyres up quicker, tyres use friction and brake heat to warm up,
i would pump them up when they are warm, that is what i do :), seems to work quit well

You didn't tell us what the vehicle tire placard says for pressure. That might affect the answers that you get.

Side wall marks are usually for cold tyres. "Cold = the open air temperature"

My tires are rated 44 PSI on the sidewalls. I keep them pumped up to 52 PSI cold. They are wearing okay, mileage is okay, car rides somewhat rougher. It's a tradeoff I can live with.

The general rule for tire manufacturers is tire pressure on the sidewall is cold and you'll get 4-6psi as the air expands during normal driving (usually in 1-2 miles). 52psi cold is significantly over the rated pressure. The most likely consequence is going to be early tread wear on the center of your tire, but it also effects traction and handling. I'd be comfortable with 4psi over in the summer, but I stick with the sidewall rating during the winter (I live in snow and ice country).

Also, realize that being 8psi over is probably not buying you more than a single MPG and maybe not even that. If you were driving around at 20psi, more than likely it would only cost you 1-1.5mpg. You're better off investing your time and energy into the grill block, driving technique and aeromods, thus saving yourself the expense of having to replace tires more often because they're wearing faster.

Cold. That's what the tires are rated for, and what the car calls for. If you set the pressure when they're hot, the next morning you're underinflated.

Tire wear: higher pressure has not worn my tires in the middle on my last three sets. I've found it to extend the life of the tires as well. These are all passenger tires, LT might be different.

my tires are rated at 50psi and I have them at 55 psi after a 5 mile drive to the station. I will be dropping them back down into the 40s soon though as I get some wicked wheel hop in the ice and snow.

I have had soft winter tires for a whole year now (used them in the summer) Other than some very rapid wear due to a very bad alignment issue they have worn flat across.

One thing tire manufacturers have to contend with is varying speeds traveled. The faster the car goes the higher the temperature of the tire. They calculate the increase in pressure for a vehicle at the max weight of the tire traveling at the speed rating of the tire.

I have not seem more than 1 psi increase in pressure from cold to hot. They seem to run cold all the time. 50 psi is 50 psi for me. Tires have steel belts around them to hold them in shape. I have never seen a tire wear out in the center from being set a few lbs over pressure. My tires are wearing flat....just like they are supposed to.

EDIT: I borrowed a friend's flat bed trailer a few months ago to haul the tractor. I checked the tires before leaving and my air gauge exploded in my hand!!!! It was an 80 lb gauge too. It had well over 150 lbs in the tires and they were wearing flat. He hauls VERY heavy loads on occasion, and so he leaves them "fully inflated". These tires are half worn down as they have seen many miles, but they are wearing flat.

speling ;)