Tire Pressures ----- What is the Current Best Practice?

[Jack Flash]

Years ago, I read an article in Road & Track which stated that, for best fuel economy and handling, tires should be inflated to the max pressure listed on the tire.

The author had spoken with engineers at GM and Ford who told him that the pressures in the manuals were chosen to give a soft ride and ok handling / fuel economy. They said increasing the pressures was fine, with the caveat that if the manual says "28 psi front, 24 psi rear" you should maintain that differential when increasing the pressures.

Fast forward to today. I bought a used Jeep a year or so ago, and noticed the tires were inflated to 40 psi. The manual says 33 psi all around. I looked at the tire sidewalls, which say 44 psi max. I have been running them at 40 psi, but I'm now inclined to go up to 44.

Anyone have any thoughts, comments, or suggestions on this subject? (I do not mean to limit the discussion to Jeeps since my wife and I have other vehicles as well).

 

[Jack Flash]

Years ago, I read an article in Road & Track which stated that, for best fuel economy and handling, tires should be inflated to the max pressure listed on the tire.

The author had spoken with engineers at GM and Ford who told him that the pressures in the manuals were chosen to give a soft ride and ok handling / fuel economy. They said increasing the pressures was fine, with the caveat that if the manual says "28 psi front, 24 psi rear" you should maintain that differential when increasing the pressures.

Fast forward to today. I bought a used Jeep a year or so ago, and noticed the tires were inflated to 40 psi. The manual says 33 psi all around. I looked at the tire sidewalls, which say 44 psi max. I have been running them at 40 psi, but I'm now inclined to go up to 44.

Anyone have any thoughts, comments, or suggestions on this subject? (I do not mean to limit the discussion to Jeeps since my wife and I have other vehicles as well).

 

[walter o]

I usually go 1 or 2 psi over the rated listing for the vehicle,as on the sticker on the door. You will get a little harder ride, but tire wear will be less . milage will be better. The engineers for the car companies list the psi for the make & model of the vehicle for specific reasons, safety, handling ,milage.The psi rating on the tires are max psi for that tire they also have a speed rating. I alaways check tire wear. Outside wear on treads =low psi ,wear in the center = hi psi.

 

[Jack Flash]

As I recall, the article claimed that this type of max inflation promotes longer tire life, better braking, and other benefits. Obviously, YMMV.

A co-worker once told me that a guy at his tire store told him that it was ok to exceed the max pressure listed on the tire by at least a few psi. I personally am reluctant to do this, but my co-worker did and claimed he had no problems.

 

[Bob R]

I guess it depends on the tire and types of tires, but the big ones on my 4x4 van I put a chalk mark across the tread and drove it. I kept adjusting pressure until the mark wore off evenly.

That may or not work for passenger tires.

bob

 

[tailgunner6]

I like to run tire pressures that give the best treadwear. Since I drive a FWD car ('00 Acura 3.2TL), I've found that a couple psi more in front and a little less in the back, specifically 38 psi F, 31 psi R, gave me the best treadwear. I haven't noticed any reduction in fuel economy (24 mpg overall) and the car handles great.

YMMV

 

[84CJ]

Run what is recomended unless you have oversize tires. The tire manufacturer recomends tire pressure on the OE tire normally after much testing with their tire on that vehicle. Proper tire pressure and differential in pressure can make the difference between spinning out and rolling over. Tire rotation is the key to long life on tire wear. The money you safe on gas by running high pressures is not worth it.

 

[DeathGrip]

I remember the Firestone/ford problem a couple of years back. The guys would inflate the tires on explorers to 28psi so "soccer mom" could think she was in a 'caddy. THEN somebody would take a trip and forget to up the pressure and..........NOT GOOD!........I suguest somewhere around the manufactures specs will work with thought about conditions and usage.

 

[jdh]

Don't.
First off max pressure will cause the center of the tire to wear faster.

Then because of the center of the tire bulging the contact patch will be smaller resulting decreased traction.

Modern cars are controlled by computers. Computers are programmed with a data set used to control the ABS among other things. One of the parameters is the coefficient of friction between the tire and the road surface. Change the contact patch you change the coefficient of friction then ABS performance is degraded and safety is compromised.

Higher pressure causes the side walls to be stiffer effecting the steering performance and causes sever under steer (push for you Nastycar types) on turn in and the back end to be loose as a goose. The result is the back end being faster than the front and you going backwards around the corner.

The tire pressure posted on the the door sticker is the best compromise between safety, ride quality, and performance. The tire companies and the auto manufacturers pay really smart people with lots and lots of credit hours big buck to figure this stuff out. Trust their wisdom.

 

[DeathGrip]

Exactly jdh, cheers!

 

[Old 44 Guy]

Several years ago Ford Explorers were rolling over after tire tread seperations. Firestone I believe. Firestone recomended 35 PSI in their tires & Ford recomended 24 to 28 PSI. I have 198,000 miles on my Explorer & always kept my tires at the tire manufacturers recomended PSI which is 35 PSI. Never had a problem.

 

[DeathGrip]

Once again S&W Forum members show there stuff! cheers to you Dick,I could'nt remember the specs.

 

[Vulcan Bob]

I run 35psi in all my four wheeler's.

 

[sonny]

Rotate 'em every 6-7000 miles. There is a treadwear rating on every tire, as well as traction and temperature ratings. Use this info if you're buying new tires.
I drive tires rated for 80,000 miles, always Michelin or Goodyear.
My last tires had 60,000 when I sold the vehicle and it was a GMC (heavy) Envoy. The tires also have a speed rating; i.e. T-rated etc which gives the mph that a tire can be run for one hour safely. Anyway, I always run at the max pressure which is on the tire. My present Michelins are t-rated, I think, and are speed-rated; good tires. Max pressure on tire is 44 psi, and that's what I run. Also, you should measure tire pressure on cold tires, not hot. Tires will be hot after about 1 mile of driving. If tires are hot, they are likely reading 2-3 psi more than if they are cold. You can read all this on ComsumerReports.org or go to library and look at their Consumer Reports annual.
Sonnytoo

 

[venomballistics]

we seem to be overlooking conditions of use here.
if your ride sees long country drives or extended freeway miles ... air expansion dictates that it may be unwise to push them to max cold pressure.
a mostly urban driven car dont see all the temp rise of a long hauler, so it can usually deal with a few extra PSI, though I dont see the advantage in it as the slower gear ratios at city speeds reduce the resolution of any measurable difference

 

[2Loud4You]

Those of you running max pressure are forgetting an important factor...heat. Heat makes air expand and therefore the air in a hot tire has now expanded beyond max pressure.

I suggest manufacturers specs but a range of a few pounds is fine. As has been pointed out in another post, tire pressure ratings are not only set for ride comfort. It's part of the bigger picture including braking a handling.

 

[m1gunner]

Originally posted by 2Loud4You:
Those of you running max pressure are forgetting an important factor...heat. Heat makes air expand and therefore the air in a hot tire has now expanded beyond max pressure.

Not quite. The "max pressure" printed on the tire sidewall is a COLD reading. You always measure tire pressure on cold tires, no pressure values are published for "hot" tires. The tire makers know hot gasses expand, and this is figured into the parameters published by the tire makers.

 

[mtb1bkr]

I'm still waiting on my pressure gauge from the president. You know, the one that will alert the police if you don't overinflate your tires to save on gas.

Bill

 

[shovelwrench]

I set my tires by how they wear. Less pressure in the rear, more in the front. The tag in the jamb has no bearing on my setting.

Currntly in my Saturn coupe I'm running 28 front, 25 rear (205-60/15). They are one size wider, same hiegth as stock.

In my truck, 87 chvy shortbed, 35 front, 30 rear (33-12.50/15).

If you watch how a new set of tires start to wear, middle or edges, and play with your pressures a bit, you gain quite a bit of handling. It also evens out the wear so you get longer tire life. It also adjusts the tire pressure for how you drive, and how the tire reacts when cornering. It also lessons the need for rotation.

If you notice your tires are wearing on the edges, add pressure, wearing in the middle, drop pressure.

It would take a mathamatition to figure out actual recommended pressure.

Look at it this way, every tire is different, even if the same size is printed on the side. The weight rating is different, the wear rating is different, the pressure listed on the tire is different. All it really boils down to is how the tire sits on the road.

So how can a car manufacturer say this pressure for this car....Its BS. And now they try to force you with the TPMS sensors.

 

[shovelwrench]

OH YEAH,
Worse gas mileage though.