Tire PSI ?
 

I have aftermarket tires and rims on my 96 LT4. The originals were 17 inch and the ones on there now are 18 inch. The sticker on the inside driver side door says to inflate to 30 PSI for the 17's. Should I add a bit more for the 18's or does it matter. I know this is pretty basic but I never really thought about it before so I just want to do it correctly so that the tires wear evenly. Thanks guys

You'll never get a guaranteed correct answer, since there are so many variables.
What is your reasoning for adding a bit just because you moved to 18's (just curious)?

I would start with what the door sticker says (even though it's for the factory tires).

There should also be a "Max" recommended pressure on the sidewall of the tire.
So, somewhere between what the door sticker lists and the Max pressure should be the best pressure for your driving conditions.

I would not go any lower than what the door sticker lists, but I wouldn't run at the Max level either.

Doesn't really matter on 17 vs 18, run them at the same pressure you have always run them. 32-35psi cold pressure is what I run.

Don't forget to change the air in the tires every 12k it gets stale. :D

my passenger side front tire was really low this mourning so when I went to add air I looked at the door sticker and it just occurred to me that the tires were bigger than stock. i just never thought about it before thats all. I put 32 psi in all of them and they seem fine. Any one interested in 96 sawblades that are in nice condition? The front tires are good, the back ones are worn out. They should also have the pressure sensors on them, which I know I should get but it seems like a big PITA. Thanks for all the replies.

Tire PSI is something you have to experiment with. It depends on what GM recommends and the tire manufacturer does. GM will want a lower PSI to make the tire sticky but the tire folks want to make sure your not running too low to damage the sidewalls and belting to make the tire come apart. An excellent example it the Ford Explorer fiasco from a few years back. Firestones came on the SUV from the factory. Ford was recommending something like 28 PSI to help with the top heavy nature of the vehicle while Firestone wanted 36. Running the tire at lower pressures weakened the tire and they would catastrophically blow out. The tires fault or Fords? That one is still debated.

I have Sumi's on my car and stamped on the side is 44PSI cold pressure. I have found this is way to much for our light cars. When you start lowering the pressure to GM specs this specific tire starts to get squirrelly because of light sidewall construction I guess. I have been playing with the PSI to balance the two. I am running about 36 PSI and watching the tire wear and the handling is good. Hopefully that will be a good balance.

I am pretty sure my 89 w/FX3 says 35psi! I store with 37-40psi over winter. My tires have 51psi max pressure, Kumho MX. For the kind of imperfect roads I drive on, 35psi is about the best compromise. Otherwise, I will track tire ruts made by dualies etc.

Running tires at low pressure was the topic of Ralph Nader's "Unsafe at Any Speed", and the car was Corvair. The pressures were really low like in the high teens.

GM cares about ride comfort. Ford should have done a better job w/
suspension design rather than focusing on making the truck ride like a car with low pressure.

I know GM softened the ride of C4 from 84 on, I guess tire pressure (30psi) was part of that. Spring rates went down over the years etc. There must be a trade off in safety vs comfort.

When i can't find the recomended tire pressure i always start with 20% less then what the max. tire pressure says on the tire

yeah, I usually do that when I change the headlight fluid