ShawnOk

iTrader: (1)

So I searched the internet looking for a tire pressure calculator. Found some for farm equipment and low speed vehicles, but nothing useful for passenger cars. I have two sets of aftermarket tires at the moment, summer and current temporary tires, and am looking for the optimal suggested tire pressure. I am having a hard time. Some sites recommend 10% less than the max load on the sidewall. Others say to use the curb weight, or axle weight, or load index. Very confusing. I've posted my specific tire specs below. Maybe someone can help me shed some light on what the optimal PSI should be on each? Thanks in advance:

Summer:
F: 245/35/20 Toyo Extensa HP 95W
R: 275/30/20 Toyo Extensa HP 97W

Temporary Summer:
F: 225/35/20 Venezia Crusade HP XL 90W
R: 245/35/20 Duran F-One XL 95W & Altenzo Sports Comforter XL 98W

texsexlex

iTrader: (3)

I don't know what the optimal psi would be for any tire. I think alot of that would be more personal preference than anything. I usually run my tires about 4or 5 lbs under the max psi that is stamped on the side of the tire.

rudyH

I don't think pressure is a function of size at all. It's pounds per square inch so the volume of the tire doesn't enter into it. As long as you have proper pressure to control excess heating and tire damage/wear you're good. Start with the recommended psi for the car as stated in the manual then you can tweak it up or down as you prefer as long as you're willing to accept that straying too far can cause wearing at the edges or in the center. I'm not being flippant but don't overthink it. If the cars riding hard, drop a couple of psi at a time. Squirmy controls or sluggish response, add a couple of psi at a time. Remember pressure changes with the tire temp when you're measuring.

http://www.tirerack.com/tires/tirete...jsp?techid=147

ShawnOk

iTrader: (1)

Thanks for all the advice everyone. And I do understand all that has been said, but I do know there is an optimal psi in which the tire company suggests a psi that prevents the best even wear and also allows for the best MPG's. As the car's optimal psi for 245/40/18 is 33psi front and rear (as indicated by the door sticker). I was hoping there was some calculator that would give the perfect psi for aftermarket tires in which size has changed. Still hoping someone finds something more tangible versus a "test and repeat" method, which is what I will have to use if nothing comes together.

SC400slide

iTrader: (11)

33-36 PSI should be fine for your tires.

tromly

I agree !

bb430

iTrader: (1)

Tire pressure has something to do with your driving style too. I run 255 35 19 and 295 30 19 and I have 35 front and 38 rear. Car feels neutral handling to me with these psi. You might want to play around with it and of course, different brands of tires with different wear numbers(softness) gives you different feels.

mandyfig

33 is the recommended psi. This is the optimal pressure to handle the type of car and the weight. depending on the type of tires you install and the driving scheme, they can vary. 33 I might say is the minimum.

neelnaik

ShawnOK, good to see a fellow Oklahoman here! Where in OK are you located, if you don't mind me asking? I'm in Norman currently.

In regard to your question, I agree with rudyH. Start with the recommended pressure in the driver's side door jamb and go from there. There really isn't any calculator to determine inflation pressure based on tire size. I wish there was, because I have been in your situation before with multiple vehicles. I wish it was that simple, but unfortunately it's not. There is just too many variables involved.

ShawnOk

iTrader: (1)

Hey Neel, I grew up Oklahoma until I moved to Kansas City for college. I lived in a few towns including Hobart, El Reno, Ada, Yukon, and Lawton/Fort Sill. I call Lawton/Fort Sill home though as my parents still live there. I now live in Chicago finishing up my 4th Year of Medical School but currently I'm in Shreveport doing my Psych rotation. I graduate in July with my MD. As for the tire pressures, I guess I will have to fall back to the "set and drive" method. Oh well. Thanks everyone for the advice!

Prasha

I run 245/35/20, at 33/36 feel needs balancing but at 40+ rides smoother....whats the logic?