tire pressure

[97OBW]

Do you follow the levels on your door, or what the actual tire says?? my door says 29front/28rear, but my tires say MAX PSI 35 (these are not stock tires, nor are they upsized)

[unverviking]

I usually do 32 psi on ALL my tires... Not too hard, not too soft...

 

When I was a mechanic, I was tought to do, while mounting 30 psi, then when it's put onto the car, it's 32 psi...

 

32 just seems to have stuck in my head when it comes to tires...

 

That's my 2 pennies worth...

[frag]

Mine are marked 44 psi max. and should be at 32 front and 30 rear according to what is written on the driver's door still.

I have had the fronts at 34 and the rears at 32 for a long time. Recently I gave the fronts 36 and the rears 34 and, even if the ride is a little harsher, the car drives and handles very well. I keep putting less air at the rear to take into account that most of the time the wagon is not loaded and that the weight at the front is heavier that at the rear (engine, engine's accessories, driver and passenger). I'll see how it turns out.

[gbhrps]

97OBW,

 

For years I've followed what the maufacturer of the car has determined was the proper tire pressures for that vehicle, and I have followed them religously. The car manufacturers have spent the time and the money to know what pressures will give the maximum performance and safety for their paricular application, and vehicle weight. The tire manufacturer doesn't know any more than some mechanic or tire jockey would, as to how a particular tire on the front or the back of a particular car will behave with a particular load, etc., etc., when so many cars can be fitted with the same tire, some safely, some not. Yes, my 02 OBW has the pressures 29 psi front and 28 back, my wife's 04 ES330 Lexus at 26 all around, my 90 Nissan 300ZX at 36 front, 33 rear, and so for my other antique cars as well...just as the manufacturers have stated in their owner's manuals. Do what you want, but it seems to me that the people who should know are the same ones who can tell you what kind of oil to use, what fuel octane is needed and what type of transmission fluid is required, etc., to get the best performance and longevity from the vehicle you bought, and still protect your warranty.

[axxiom]

The posted tire pressure for my 2000 Legacy GT is 32 front and 30 rear. I keep the tires at 35 front and 33 rear, since I became aware of faster tire wear(an AWD trait, it seems). I've had no problems resulting from the increased tire pressure. The 3 extra pounds of pressure per tire also seems to give me better handling and a slightly firmer ride. For my taste, the GT's ride(at least for the 2000 model) is a little too soft and bouncy, which makes for slightly unstable handling at higher speeds, especially when going over undulating patches of asphalt. (I'd really love to have a firmer, more performance oriented suspension.)

[kevinsUBARU]

37 all around...2001 Legacy L wagon

 

[nipper]

I usually do 32 psi on ALL my tires... Not too hard, not too soft...

 

When I was a mechanic, I was tought to do, while mounting 30 psi, then when it's put onto the car, it's 32 psi...

 

32 just seems to have stuck in my head when it comes to tires...

 

That's my 2 pennies worth...

 

You always go by whats on the tire, the sticker on the car only applies to the orignal tires. A car that says 30 psi on the sticker that has a new set of tires on it that say 38psi, thats a dangerous situation.

This is very important, especially with Subarus, because we tend to keep them forever. My 1988 had a tire pressure rating of 28psi, but when the car was 13 years old, I had Doodyear aquatreads on it, which was rated at 38psi. I would always come out of The oil change place with 4 flats.

 

nipper

[kevinsUBARU]

I believe the max pressure for a RE92 is 44psi.

[mikkl]

Does the manufacturer of your tires provide a recommendation for your car?

 

If not, I would start with the pressures recommended on the car's sticker and keep a close eye on the treadwear. If the corners start wearing faster than in the center of the tread, put in a bit more air. If the center wears more quickly, let some air out. If the tread wears evenly, you got it right.

 

It may also depend on how heavily you load the car. When I was in Europe, my cars had two ratings for the tires--the normal one driver commuter setting and the fully loaded on vacation setting. The vacation setting was typically a couple of psi higher. There may be something similar in the owner's manual.

 

Tirerack has some interesting articles that talk about tire pressure and driving styles. You may find them of interest. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1

 

HTH,

 

mikkl

[nipper]

Hunting around I found this..

 

http://www.sportcompactcarweb.com/tech/0208scc_tires/

 

and a formula (we all lve formulas)

 

In the event that you aren't able to find a recommendation for your car, or the tires on your car are so different from those that were originally fitted from the manufacturer as to be incomparable, we received the following rule of thumb from Oscar Pereda, an engineer for BFGoodrich. He calls it a "realistic starting point," saying it has never been just right, but is a good place to start. The rule is:

(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.

Example: Stock 911, 3,000 lb.

(3000/100) = 30 psi

Add 2 psi all around = 32 psi

Add 2 psi to heavy end = 34 psi at rear

With modified suspension, the result is 30 psi front, 32 psi rear.

 

 

Seems like there is no set rule on air pressure, if you read the article. I have always gone by whats on the tire. I always had tires last 3-4 years ( I drive a lot) and gotten good gas milage.

 

nipper

[BigMattyD]

I think it is best to stay in the range recommended by the car manufacturer when it comes to tire pressure, as long as you are using stock size tires and running the car on normal, paved roads.

 

 

The max. pressure listed on the sidewall of the tire is just that: the max. pressure the tire is rated for. Depending on the amount of weight that is being put on each tire, the optimum inflation will vary. If the weight is heavier, you will need more pressure to maintain the desired shape and profile of the tire. If the car is lighter, you will need less pressure to achieve the same result.

 

On my motorcycle that only has two, relatively narrow, tires, the placard has a table of different tire pressures to use for front and back depending on the amount of weight on the bike, and the type of driving (constant high-speed vs. city driving.)

 

The faster and heavier you are, the higher the pressures.

 

Makes sense.

 

Matt

[mwatt]

You always go by whats on the tire, the sticker on the car only applies to the orignal tires. A car that says 30 psi on the sticker that has a new set of tires on it that say 38psi, thats a dangerous situation.

This is very important, especially with Subarus, because we tend to keep them forever. My 1988 had a tire pressure rating of 28psi, but when the car was 13 years old, I had Doodyear aquatreads on it, which was rated at 38psi. I would always come out of The oil change place with 4 flats.

 

nipper

 

Nipper, I don't think that's correct. What's on the sidewall of a tire is the maximum amount of air that the tire should safely hold, no matter what kind of car that tire is installed on. You should adhere to the pressures shown on the label that the manufacturer applies to the vehicle (at least, if you're installing original-size tires). As GBHRPS indicates in a previous post, manufacturers do a considerable amount of research to determine the tire pressure that provides the best combination of safety, handling, ride characteristics, and tire life for that particular vehicle.

I do see, however, that the latest trend seems to be to inflate the tires a little bit over the manufacturer's recommendations to save fuel. But I still firmly believe that the number cast into the sidewall of a tire is only a maximum for that tire.

[Tiny Clark]

My only problem with running what the car has posted on it is that the outside edges of the tires seem to wear faster. The car manufacturers always take ride softness into account, so a little less pressure yields a better ride.

 

I stick to 32 all the way around.

[1 Lucky Texan]

My only problem with running what the car has posted on it is that the outside edges of the tires seem to wear faster. The car manufacturers always take ride softness into account, so a little less pressure yields a better ride.

 

I stick to 32 all the way around.

 

Aside from reports of Foresters delivered with high pressure, I think you're correct, that the manufacturers would like you to experience a soft ride. I've found on the few cars I've owned in my life that , on average, about 10% over the rec. pressures gives me the most even wear. I'm sure there must be exceptions and watching the tire wear and monitoring handling/ride quality is the best approach.

[nipper]

Nipper, I don't think that's correct. What's on the sidewall of a tire is the maximum amount of air that the tire should safely hold, no matter what kind of car that tire is installed on. You should adhere to the pressures shown on the label that the manufacturer applies to the vehicle (at least, if you're installing original-size tires). As GBHRPS indicates in a previous post, manufacturers do a considerable amount of research to determine the tire pressure that provides the best combination of safety, handling, ride characteristics, and tire life for that particular vehicle.

I do see, however, that the latest trend seems to be to inflate the tires a little bit over the manufacturer's recommendations to save fuel. But I still firmly believe that the number cast into the sidewall of a tire is only a maximum for that tire.

 

Actually the tire pressure on the side of the tires i have now BF Goodrich have a cold pressure an a max pressure. I always go by the cold.

[cookie]

than I can. I'll try to post a link.

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=72&currentpage=1

[skydvejam]

OK here are my 2 cents worth from some experance racing, not subs yet, and it has been on many diffrent surfaces.

 

High speeds, cold surface= highest psi

High speeds, hot surface= lower psi

Highway speeds, any temp= lower still psi

Lower racing speeds = lower still psi (at the cost of tire life though)

Off road, crauling ect. ect.= Very low psi

Here is what happens with the changes, with higher PSI your tire contact patch at first is smaller, less tire is on the ground, as you start moving though that patch causes friction, and that increases presure in your tires. Now you also have to take into account the ambent presure that you are operating in. Then also you have the fact that as you add presure your sidwals get stiffer, that increses your corning to a point, unless your sidewall is built for lower presures.

 

 

So to sum it all up, the max psi on the tire is NOT what your tires should be at, you will have new tires on the sides and nothing in the middle, the best presure is from a lot of diffrent factors of how you use your car.