Inflation pressure

[ontarian_frog]

I was making an inflation chart last night and stumbled upon a problem.

Like most front wheel drive cars, the Aveo is front heavy. I did a little research and came up with 60/40 (front/rear) weight distribution for a front wheel drive car.

Well the problem is this. GM says to inflate the tires to 30 psi each. But the front tires support almost 300lbs/each more than the rear ones. Wouldn't the front tires require more pressure than the rear tires?

After reading some more, it would seem like the opinion of many is that most car manufacturers do not make good recommendation and that more psi is needed.

I also stumbled upon the rule of MAX -10% (In our case this would mean 44psi - 10% (4.4) = 39.6 psi). A guy had about four cars and tried it and it worked out to about 1 or 2 psi close to where he likes to run his tires. Last summer I ran my tires at 37 psi, no problem, put 6000 miles on them and I can't see anything suggesting overinflation wear.

What do you guys think?

[virtualdemo]

Personally I put the PSI that the TIRE company puts on the tire minus the 10% like you mentioned. If we all went with the dealer recommendation it would be wrong in IMHO. When you buy new tires that are non OE spec do you still put in what the owners manual says? I hope not. I have an F150 with tires larger than normal and they have a 65 PSI MAX Rating, I do not run them at the "recommended" 35 PSI. So I know there is another thread about this and I am gonna shut up now....lol

[mtlswift]

I run different pressures front and back... It's the right way to go...
31 rear and 35 up front for me, but these are on 175 width tires. I'd probably run a bit higher on 185s...

[ontarian_frog]

That's pretty what is close to what I saw in my calculations. What would be ideal would be the contact patch being the same size in the front and in the back, so you get even wear on the tires (don't forget tire rotations).

Now here comes the fun part. Determining which contact patch size is the best for the Aveo. Since I wasn't able to find a formula which would tell me when the tire is bulged, I'm going to have to wait and do some testing during spring or summer.

Trick is to draw a line, perpendicular to the forward movement of the car and drive in a straight line a little to see if all the chalk is gone. If it's all gone, the tire is properly inflated. If someone in a 'warm' state can do this, I won't have to wait so long

Of course using that method, you might find a range of good inflation because tires are a little bit forgiving (ie: sidewall stiffness).

[AVE0SAM]

i run mine at 40 psi on the stock wheels and they are fine