Need help.

[Nettle]

I don't know my recommended tire pressure!

I have a '98 Subaru Legacy Outback. The manual says to check the bottom of the driver door, but the sticker doesn't have anything on it. My tires say a max of 44psi and everyone I ask says to keep pressure at 32. I read here that increasing tire pressure is good for mileage, but I'm afraid to do so because I don't know what should be (and I also heard of the front and back tires being different).

Help, thanks!

[Pontiac]

Inflating is good for mileage, but bad for the tires. Same for underinflating the tires. Bad for mileage AND bad for tires.

32 PSI does sound correct for most car tires. Maybe a bit more for winter driving, but thats going to matter on the regular temperatures in your area. Fortunate for you, you have a sticker. You should see something in kpa (Kilopascal) or psi (Pounds per Square Inch).

A quick google search will give you the conversion.

[bates]

Check the door frame, low on the aft (rear) vertical pillar or post, that is the most common place for the sticker. That being said, my 2000 Acura Integra's recommended pressure is 36 PSI. I've been buying tires rated for 44 PSI, I find that 44 PSI is an acceptable ride for me and tend to inflate the tires to that level, it does help some with mileage to keep your tire pressure high. My wife doesn't like the ride in her minivan when I inflate hers to recommended pressure so I tend to run hers at about 40 PSI, harder than the 36 that Mazda recommends, but less than the 44 that Michelin rates the tires for. As for wear, you'll find that your tires will wear better at a higher pressure as long as it doesn't exceed the rated pressure for the tire. If you run 44 PSI tires at 32, you'll experience shoulder wear and your tires will require replacement due to tread wear before the center of the tread has worn out. If you over inflate your tires you'll experience center line wear and the middle of the tread will wear out before the shoulders do. Properly inflated tires should wear evenly, with the shoulders and the center of the tread all nearing the wear marks at about the same time. Also, don't forget to rotate your tires, check the pressure at least once a month (and always check your spare at the same time) and get them in for a balance if you get any feedback from the steering wheel, especially when braking. A balance is a lot cheaper than a new pair of tires and an unbalanced tire can wear severely in just a few thousand miles.

Good luck, don't be afraid to try a little higher pressure and see how your car rides and feels. If you don't like it you can always air down back to your 32 PSI, just make sure that you add air and check the pressure when your tires are cold, first thing in the morning before you drive the car. The pressure will increase after driving and give you an in accurate reading.

[VWJunky]

One note I leared from a racing guy was that the tire pressure max the company puts on there tires is really not the REAL max the tire can take before blowing up so don't worry about that unless you have bad tires and that is a whole different story.

I did auto cross with my jetta one time and the race guy said to run 50psi up on my front tires and like 20 on the rear! This was a older 86 jetta with Front wheel drive, it helped me as the front dived hard in turns and the rear end would slide around a bit.

[rem83]

I generally wouldn't run my tire pressure at more than 2-4 psi above the vehicle manufacturer rated pressure. Just because a tire can take 44 psi doesn't mean that's the best pressure to run at - it can adversely affect wear as well as traction (and ride quality).

Also, please make sure it is alright to rotate your tires before you go ahead and rotate them. I have an '85 BMW 3-series - it says in the owners manual "Do not rotate tires." I did not check this, and rotated the tires right after I got the car. I ended up spinning it into a guard rail on a highway exit ramp because there was essentially no traction on the rear wheels (caused by different wear patterns on the front and rear).

Your factory owners manual / shop manual / door panel sticker has the best information for your specific vehicle. If you don't have access to any of these, you can also try calling your dealer, although sometimes they'll blow smoke up your *** just to get you off the phone.

[Smitty]

Also, keep in mind that tire pressures change as the tire heats up. My low-profile (215/40/18) tires can gain 7-8 psi as they heat-cycle. I like to keep my tire pressures a bit higher than the recommended pressure -- usually around 36 psi cold. I find that this level is a good compromise between handling, wear characteristics and fuel economy.

[naughtybeaver]

You know I have read about the tire pressure recommendation, and all of the other recommendations for getting better gas mileage. The only thing that I've found that has a significant effect on mileage for me has been to SLOW down. I know that is tough to do these days, but I slide on over to the slow lane, set my cruise control between 55 and 60 mph, and I'm good to go. From my records if I drive like most people do, FAST, I'm only going to be getting 25-28 mpg. If I drive slower, and with my cruise control, I'll get around 35-37 mpg. You are going to have people getting angry at you for driving slow, but if you keep it in the slow lane let them go around. Most of the time it is people who are trying to use the slow lane as a fast lane that are getting frustrated with you. It could be worse, you could be like some knuckleheads and drive slow in the fast lane.

I always ask myself when I see someone inflating their tires, "Now that they have taken the time to inflate their tires, I wonder how fast they drive?" It kind of seems crazy to be worrying about inflating your tires if you're just going to go out and drive like a bat outa heck. It's like those people that go to the fast food restaurant, order 2 double-bacon cheeseburgers, an order of fries, and a diet coke. Duh!!

[Nettle]

There's absolutely nothing anywhere on my car that says what the tire pressure should be, but I think I'll go with what ya'll said. Thanks!

[rem83]

@naughtybeaver - You should keep your tire pressure at the correct setting regardless of whether you think it will improve your gas mileage or not. If you are running the incorrect pressure, your tires will wear pre-maturely and you are more prone to blowouts.

As far as economy goes, low tire pressure increases something called the rolling resistance of the tire. This force is pretty much independent of speed, so you won't see it's effects very much at higher speeds where drag dominates. Also, I'm not certain how much tire pressure changes rolling resistance, but rolling resistance itself is not a negligible component of the losses which result in fuel consumption. Unfortunately, there isn't a whole lot you can do to reduce rolling resistance - it's an unavoidable result of having a tire contact patch, and that's pretty much necessary to be able to accelerate, brake and turn.

[naughtybeaver]

Hey Rem83! I agree with you completely on keeping the tire pressure at the correct setting. If I came across sounding like I am recommending not keeping tires properly inflated that was not my intention. I was just pointing out that it does seem like many folks are focusing primarily on proper tire pressure in order to get better gas mileage, and sharing my thoughts on that. It's definitely a good idea to keep tires properly inflated regardless of whether or not it affects gas mileage.

Have an awesome day everyone!!