I have a '99 convertible V6. I bought it used and the last owner has custom tires on the car. They're Sumitomo tubeless 245/40-18 tires. I know what is the recommended tire pressure for the standard tires, but considering that these are tubeless + bigger tires than the standard ones that came with the car, what would be the recommended pressure for these tires?

 

Look on the sidewall

 

Usually tires run between 30-34 PSI or so, but yeah sometimes they say on the side.

 

That's the thing. It doesn't say on the sidewall. It only indicates max pressure as 52 psi.

 

Id say 30-34, id say try one of those ranges and you oughta be good, you never go with max psi though

 

That's the max psi you should inflate the tire to, not what psi you should run for best wear and contact patch. That info is located on the side of the drivers door.

 

True Dustin, but i think he said he's running a other-than-factory size tire, so would the recommended tire pressure inside the door still be accurate? Curious bout that myself actually. i run like 40 psi in mine.

 

Usually not, but if it works good for his tires than go for it and ive never seen a tire run 40psi and be correct o.O

 

Well on my particular tires, the MAX recommended pressure is 51 psi i think. So with that being said, wut would you recommend for an operating pressure?

 

That's exactly my point. I think I've heard from somewhere that tubeless tires need less psi. That's why I wonder if Ford's suggested pressure would work with my tire or should I use less psi. The original tires were even smaller, they were 16 inches, I believe.

 

Its hard to say without knowing what rim size and tire sizes you are running. Generally on mustangs 30-32psi makes for even wear and good tread life and traction. 40psi is to much and I'm willing to bet the middle of your tires are wearing out much faster then the outsides, correct?

But if you run oversized tires like I do with 275/40/17's on a 17x8 rim. If I run 30psi the middle wears out very fast. I run them at 20-22psi for better wear because of their large size on that small width rim.

 

Well... i dunno bout him but i do run 275/40/17's on factory bullitt wheels. As for wear pattern, the tires are only a few weeks old, so please if im runnin the improper air pressure what do i need to correct it to Dustin? Oh yeah, i run 245/45's on the front.

 

I posted what I run my 275's on stock 8" rims right above you.

 

Oops. LOL So you did. You run 20-22 in the 245/45's on the front as well? Or 30-32?

 

This is a topic I've kind of been looking for for a while because I just checked my air pressure the other day to make sure they were just right. My car placard says that the stock 245/45ZR/17's (up front) should be run at 30 PSI. The sixteen in tires available to the mustangs should be run at 35 PSI, and the spare at, I do believe, 60. But, they don't give a size for the rears, 275/40. I'm assuming 30 would be the winner, but I'd either like to see it in writing or at least have someone confirm my theory; the two sizes are pretty damn close.

But does it matter that my front tires are shitty all-seasons and my rears Nitto's? The placard states that for that tire pressure to be used, the tire must be replaced with a tire of that speed rating, and I doubt my non-ZR front tires have the same speed rating; why would they? My tires are shot to hell and being replaced in the spring with a wheel and tire combo, but for now I'm just curious as to the correct pressure to use. I just went with 30 all the way around.

 

I looked and my Bullitt only has a sticker inside the driver side door jamb. And only lists manufactured date and gross vehicle weight. Nothing about tire psi.

 

It lists psi on my car.

The tire pressure I listed is for running 275/40/17 tires (brand doesn't matter) on a 17x8" rim. 20-22psi makes for best wear and traction. Front stock 245/45/17 on stock 17x8" rims seem to like 30-32psi.

The reason you need less psi on in the 275's is that they are over sized for the rim and so because they bulge out you need to run less psi to make them wear good.

 

look more...there may be a different label...on the door itself.

 

I found my lil tire pressure sticker thingy, its in the glove box. Yeah i dropped the rears to 22 (it sure makes em look like they're goin flat tho lol) and the fronts to 32. We'll see how that works out. Thanks Dustin, you're always a great help dude!

 

Spike is right; if I'm not mistaken, the PSI placard is on the passenger's side door jam.

On a side note, does my stock '00 GT have 17x8's all around? I always thought the rears were 17x9 seeing as how I have 275/40's in the back and 245/40's up front.

 

I would not run 22 psi in a street tire.... it will damagel sidewall from the inside from the flexing since the pressure is so low.

 

What pressures are you running front and rear Zig? I assume you run 275/40's rear and 245/45's front...

 

It will be fine I have been doing it for 4 years. If you don't run them lower like that they will not wear even and you won't be getting the best traction possible.

 

ok then 22-32 it is. LOL