I was wondering...and this might seem like a stupid question...but here goes.
A lot of us have replaced our wheel/tire combos with stuff that wasn't original to the car. On the stock wheels/tires, the manufacturer's recommendations are on the tire pressure guide, in the owner's manual or the sticker. But when you change the wheels and tires, sometimes drastically, how do you know the proper tire air pressure to maintain? I always inspect my tires for wear, but it seems that if it shows up on the tire as wear, its already a little too late. Any good "rule of thumb" besides trial and error?

Hi Steve - this has come up in the past and there are a couple sides to this. One is run the vehicle manufactures recomendation no matter what. The idea being the vehicle was designed to be carried with their recomendation for safety. I don't suscribe to that though. I believe the manufactures recomendation is for the tires that came on the vehicle.

I have had many types of vehicles over the years from econo boxes to sports cars to 3/4 ton heavy duty trucks and a lot somewhere in between. Most got some kind of wheel and tire treetment. As a youngster to improve handling and traction a little we put a few more pounds of air in the rears and a few lbs less in the fronts, this compensated a little for the front starting to push. Using my trucks to haul loads and for towing I always added air to the rears when putting a load on the truck. When I towed a travel trailer with a load leveler hitch I upped the air in all 4 tires. a common tip to help gas mileage is to increase the pressure in the tires to reduce rolling resistance. You can see I adjust pressure to suit the conditions.

Now if you look on the side of the tire you will see a cold inflation maximum and I never recomend running more than the max. For some reason, ever since radials came out I've had this magic number of 32psi in my head. I use that as the proper inflation rate for all around driving. Maybe 30 in front and 32 in rear even if the tires are rated for more unless the car is loaded down then I add more but never over the tires rating and also cold tires only.

The thing to always keep in mind is tire pressure can effect how a car handles so be aware when pressure changes are made so you are not caught off guard. Watching for tread wear is important too but you have to be really obervent, if you are just looking down from 6 feet above the tire it will be too late by the time you notice a pattern.

Maybe more than you wanted and I'm sure others will pipe up, they always have on this subject in the past...

No, this is great. Its exactly the kind of info I'm looking for. When I had my tires replaced at Just Tires, I had this same discussion with two of the guys who work there. One guy said that no matter what wheel/tire combo you go with, still use the manufacturer's recommendations. The other guy, the store manager, said to read the sidewall of the tire, and just like you said, don't exceed the cold tire max pressure. And both these guys work in the same place!

I recently read an article, (can't remember the mag, I was at my doctors office), but it did all sorts of tests and the consensis was; better high than low. Even a few lbs. made a difference in hydro-planing tests :eek:

John