Invertalon

I was just wondering what tire pressure I should use with my new tires/wheels. I see on the sidewall it says do not exceed 40PSI while the beads are seating, but it also has a "max press" of 50PSI.

I was running my stock tires at 40PSI all around and the wear was excellent (sidewall max was 44PSI).

I was just wondering what I should run, up to 40PSI or 50PSI?

Thanks for the help! They are Falken 912 tires btw, 225/45-17's on 17x7 wheel.

IH8ONYU

use 40... dont use the "max" pressure...
typically you should be around the 35-40psi range.. but dont inflate to "max" psi for daily driving

Invertalon

I guess my real question was, which do I follow as the max pressure? The 40PSI for "bed seating" or the 50PSI for "max press"?

IH8ONYU

the max pressure is 50psi.. dont exceed 50psi..
the bead are seated

just remember though, that as the tires get hot when you drive, the air inside them gets hot, and expands, and the psi goes up, so if you fill your tires to the "max pressure" of 50 when the tires are cold, you are gonna risk a blowout when the tires heat up (unlikely but plausible). you should look on line at the manufactures website, usually they list the "recomended" inflation range, and the "max" inflation pressure.

But yes, the MAX pressure is 50, dont exceed that..

rockthebeef

I also have 17x7 and Falken 912s, but I have 205/50/17. I used to run the stock tires at 35f/32r just like the manual says. The tire shop that mounted my new rims put 40 PSI all around. The car handled nicely but was a little jittery. I now run 38/35 and it rides nice with even wear.

I've asked this question before and never got a definite answer. There are too many factors to consider that make it hard to give pressure specs. You have to consider the car's weight distribution and the tires' load carrying ability. I suppose you can get all geeked out and figure out a formula, but I never did. It was easier to use trial and error and use my butt as the calibrator during road tests.

Invertalon

Ok sounds good guys, thanks! I just saw the two PSI limits and was curious to what was the actual "limit".

I have it at 40 front 38 rear now, might bump it up to 44/46 (r/f). They came from discount tire at about 48PSI each, so that is why I was so curious what was "right".

Thanks again

draxcaliber

you use the manufacturer recommended tire pressure located on the driver side door sill on your car.

you can lower the psi if you want more tire grip, or raise it if you want better gas mileage.

rockthebeef

The thing is (and I could be totally wrong here) is that the manufacturer's specs are for 205/55/16 tires. When you go lower profile, I think the PSI needs to go up.

The only reason I have this logic comes from bicycling. Road bikes typically need 90-100 PSI and mountain bikes can get away with much less (30-50 PSI). Of course, there's more to it than that (on-road vs off-road), but I think when you go to less air volume you need to raise the pressure to achieve the same load carrying ability.

For the guys with the TRD 19" wheels, did the dealer put a new sticker on the car for PSI ratings? Did they recommend anything at all?

Go_HIN

Scion xB stock weight = approx 3000 lbs divide by 100 = 30
add 2 psi all around = 32 psi all around
then add 2 psi to the heavy end.... for front engine cars add 2 psi to the front tires.

front = 34 psi
rear = 32 psi

then you have to factor in your environment cold or hot climates vary a bit. But it all boils down to the driver and how you like your car to feel, vary it in 2 degree increments. Those with suspension mods may like to ride with a bit lower tire pressures.

You can look at the side of your door panel and look at the suggested manufactured tire pressure.

most tires all say load max 44psi so don't follow that, its just an industry standard in the tire community to put that as a warning. That doesn't mean load it up to 44psi. Tire pressure has mroe to do with the cars actual weight w/ variables in handling vs mileage.

I run at Front 36 and Rear 35 since the engine's not too heavy to begin with and I usually have the kids in the back as well as groceries on top of the system (3 amps, 2 subs, and wood box). I do have coilover's but I'm hoping I can squeeze some mileage outta the car. I got significant increase in mileage when I raised the car a few inches, I used to be tucking tire and ran 32/30.

had I known someone would ask this type of question I would of taken down some numbers so I could give a better accurate info.

Hope this helps!

rockthebeef

Thanks for that info Go HIN. Those seem like great guidelines. I might try bumping my pressure down a little and see what that does for mileage and tire wear. Actually I kinda don't care about tire wear at this point. I've got 10k on my current set and have been thinkng about a change...

Go_HIN

no problem! I'm actually glad you asked the question... there's alot of threads asking about getting a better ride or better handling etc etc..... most people over look the most important part on your car..... you're tires. It's the 1 part on your car that makes contact with the tarmac.... definitely not a part I'd ever go cheap on. You can have everything on your car done but if you can't make traction you're gonna get wall checked.

Most of the questions trying to improve handling could probably be fixed if people just got better tires and played around with their tire sizes. I doubt most of the members drive they're cars hard enough to really need half the things they're all talking about. But I think its more of a psychological complex much like when people get exhausts and think they're cars are going quicker. You put on a new part and you're psyche is more aware of the details in your cars performance, so you think you've improved something.... most of the time we phase ourselves.

I run on the twisties when I'm bored and I'm pretty much at my limit when I hear my tires beginning to screech. I dont have sway bars, or tie rods, bushings etc.... simply because I enjoy a nice comfortable ride. =) I dont ever kick my car out because, well its a FWD car. So I've never really found much use for the other mods for my purposes...

Zsanz

42 psi here with a 17x45 sidewall...good wear...good in the corners...?