Tire PSI for 225/45-17's
 

So on my summer tires which are 225/45-17's. Should I run the same pressure as the stock 225/50-16's or should it be different?

Re: Tire PSI for 225/45-17's
 

That's going to vary by tire model and by what you want the tires to do. We need a lot more information.

Re: Tire PSI for 225/45-17's
 

What Rob said. I run my 245/40/17's at 40 front, 35 rear because I find the General Exclaim UHP's a little on the mushy side.

Re: Tire PSI for 225/45-17's
 

I have 225/50/16 Pirelli P Zero Neros that I typically keep at 40psi front and 38psi rear for a balance between a firm and smooth ride.

Come winter, I use 205/55/16 Bridgestone Blizzaks somewhere in the mid 30s.

I also have 245/40/17 Bridgestone RE01Rs for autocross days, running 40-44psi depending on track conditions, and there's never any appropriate match front to back. At Cherry Valley (our local kart track), I bump the front right tire 2psi because of the track's shape!

My science? Best guess and feel for initial setting, and manufacturer's recommendation for proportion.

Re: Tire PSI for 225/45-17's
 

I have the Kumho Ecsta ASX. The door sticker for the stock size is F33 R29 and that's the pressure I use for my winter tires. Since these are a different size I wasn't sure. I just want to make sure I don't run them too low because of heat build up or too high and cause them to wear out too fast.

Re: Tire PSI for 225/45-17's
 

You can just put in whatever the max. is on the tire (it'll say in small print right on it) and then just subtract a few psi (4-ish) from the rear tires.

Re: Tire PSI for 225/45-17's
 

:confused:Sorry, I'm not running my tires at 51 PSI. That much air won't do you any good except cause the center of the tires to wear out much sooner.

Re: Tire PSI for 225/45-17's
 

I've actually replaced a lot of low-profile tires because people wear them out prematurely because of UNDER-inflation. If you're not sure what to run in your tires, you can never go wrong with what is written ON the tire. Why else would they put it there? 51 is a bit high for MOST cars though, unless your car is heavy. With a 51psi tire, you'd want to keep at least 40 in it, in my opinion.

I'm doing a saab 9-3 tomorrow actually that has 225/45-17's on it, and they wore out because he didn't keep enough air in them.

Guess he thought 32psi was enough in a 44psi tire...

Re: Tire PSI for 225/45-17's
 

You mean to tell me that there are different tire pressures for different tire sizes? I always thought that you go by what is on the door jam, no matter what size tire you put on the car?

Re: Tire PSI for 225/45-17's
 

I always treated the listed pressure on the tire as the maximum cold pressure for ANY fitment. That is not really a specific recommendation for any specific car.

I've always heard that proper inflation pressure depends on weight and weight distribution, as well as torque application. FWD vs RWD, or a predominantly front heavy car, or a heavy car compared to a light weight car...

There is no way in the world I would put 40PSI in my Miata's Toyo 215-45-16 T1-Rs... The stock recommendation is 28psi front and rear due to even weight distribution (with passenger/driver) and rear torque application. I usually keep it between 30 and 32, depending on how I watch the tires wearing, especially when I rotate them.

My Legacy similarly recommends 34-32 front rear, IIRC, but I usually go a few pounds above that, due to the low profile of the 225-40-18 General Exclaims... but the suspension is harsh enough, without pushing tire pressure above 40psi. 36-37 front, ~35 rear seems to handle, and wear well. Over-inflation will wear the center of the tire tread faster. Under inflation will wear both shoulders faster, if the alignment isn't causing other wear patterns or cupping.

Max inflation is not necessarily the same as appropriate inflation for a specific application. My Legacy certainly doesn't weigh as much as a G8 GT wearing the same tires, but weighing at least 600 more pounds. (and having to accelerate and decelerate that weight.)

Re: Tire PSI for 225/45-17's
 

I can agree that max. inflation on the tire and recommended inflation for your car can vary. (I too would see no reason to run 40 psi in a miata.) However, max. inflation pressure (of the tire) will almost always get you the longest life and the best mileage. It may not ride or handle the best though, because weight and handling characteristics would certainly vary from car to car.

Re: Tire PSI for 225/45-17's
 

I agree with most of that, except the longest life bit...

A hard tire has less flex, and thus less rolling resistance...

But an over-inflated tire tries to "go donut" and the pressure in the center of the tread causes the center to wear faster. Conversely, under-inflated tires cup inward at the center, and all the weight and wear kills the shoulders of the tires first, unless camber or toe wears the inner shoulder even faster.

I unfortunately have experience with over-inflation. My previous car was a Ford Ranger pickup, with original goodyears... that had been over-inflated for some time, especially the rear tires. They likely inflated the tires to hold a bed full of stuff, and pumped them way up, then ran the truck with no cargo for a while, with the rear end really light.

The shoulders looked normally worn for the tires apparent age, but the center treat was worn well past the wear bars. It got a new set of dueler revos as soon as I saved for them.

Re: Tire PSI for 225/45-17's
 

Autocross is a good one. :cool:

Re: Tire PSI for 225/45-17's
 

Well, I don't autocross the car.

But even then, it seems like it would harm ultimate grip to inflate that high, on a car so light. At a certain point, the inflexibility of the carcass over-powers the rubber's tacky grip, and slides the tire. Some of that might be good...

I dunno. Like I said, I don't autocross, so maybe people do inflate the tires that hard on a 23-2400lb car, and it doesn't act like riding on the edge of a rolling hockey puck.

Re: Tire PSI for 225/45-17's
 

I can agree that maybe the "longest life" part was maybe a bit much, because if you're not near the max weight rating, then a lower pressure can give just as much life.

When I think of "over-inflated" I generally think of people exceeding the TIRES maximum pressure, which we do also see frequently.