My HHR has of course after market wheels on it and is lowered...Do I go by the PSI on the inside of the door or on my tires? Or does it change it all since its lowered? If you can tell I don't know much about cars, just how to make them sexy, haha.

 

Just like on any car you buy, go by the PSI listed on the door. It has a lot to do with the vehicle's weight

 

yes and no because the aftermarket tires are most likely low profile so go by what it says on that tire. The stock tires are tall and such and the ones you have on your rims are low pro correct?? Stick to the max load on the tire when going aftermarket. If youre stock then stick with door

 

Actually, not correct. I'd never run a tire on a car at the max PSI.

If you want to be accurate, inflate to the markings on the door. Chalk the tread across fully and roll the car a couple of full rotations of the tires. Take a look at the markings on the ground. If the center is more pronounced thatn the outer edge, you need to let some air out and retest. If the outer edges are more pronounced, you need to add air. But the listed PSI on the door jamb will start you in the right direction.

Max pressure is just that, the most you can safely put in it. In too light of a car, it will ride and handle like crap.

 

Thanks for all the advice yall guys!

 

Exactly right solman, the max pressure on a tire is the pressure the tire can withstand without failing during the mounting process. If a tire installer reads the sidewall he/she can know that they can safely use say 55psi to seat the beads without the possibility of the tire blowing up in their face....an unforgettable and occasionally fatal experience. Either use the inflation pressure indicated on the door sticker or use your method which is a very valid one and dates to the golden age of rodding.

 

Sorry, but this is some bad information right here. You NEVER want to run your tires at max pressure

 

as you drive the tire will expand and gain pressure, if its a hot day on asphalt you can blow a tire a lot of people will overload the car when going on vacation and overthe tire pressure can cause a disater, never inflate to the max. safe driveing.