Originally Posted by Panther427

So lets see here... yes yes and no no...... the factory psi rating was technically devolped for the tires that came on it from the factory.. Now yes GM, i'm sure thought of other tires will be use on this car lets get a good all around preasure to use.. However there are SEVERAL things that you should take into consideration.... The number one most important thing in my book is weight,,,,,, AS in how much extra weight do you normally carry around. IF its just you in the car at all times that great run it at factory spec.. But i have noticed most of the tires at least in the GXP's have higher than normal max preausres vs 55-65 series tires. 45 to 50psi max is fairly common. And with thin side walls its good to have some extra psi to equallize the force..
I also run at least 2 more psi than the door sticker. but that puts me at 32psi for my TPMS and most gauges are reading like 36psi...

Every tire is different so once tire at 40 will be great, your next set wont handle for crap at 40 or 30 but like to be at 34.. So yes the door jam sticker is a starting point... but we are on here to modify our cars.. what easier than tire air preasure.

I like having extra couple psi in my tires because i never know when ill be caring extra weight and slight improvement in gas milage.

And as for airing down street tires. I have been trying different psi at the track.. i find a few psi lost has worked for me so far...even with our short side walls it seems to still allow a bit for contact patch and sidewall flex. though still experimenting... Then again when i air down its generally from a higher preasure to begin with

Originally Posted by Panther427

However you have to be careful as there are several tires that are in our sizes are of the XL or xtra load capacity. So you also need to check tires rated capacity @ psi vs. what is recomended on the door sticker and your vehicles weight.