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What is the Ideal Tire Pressure?

Dial tire pressure gauge.
Stick-type tire pressure gauge.
Bicycle pump with pressure gauge.
A woman filling her tires up with air.
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  • Written By: Brendan McGuigan
  • Edited By: Bronwyn Harris
  • Last Modified Date: 14 March 2014
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Tire pressure is usually used to refer to cold inflation pressure, the pressure of air in your tires when they are cold and haven’t heated up from driving. This affects the longevity of your tires, and your gas mileage, and having the ideal pressure is safer than running on tires that are overinflated or underinflated. When your tires are inflated properly, they will handle better and hold the road better, making your entire driving experience more pleasurable and safer.

First, of course, you need to find out what the ideal tire pressure for your car is. If you look at the tires themselves, you will see a pressure listed. In the United States this is usually expressed as Pounds per Square Inch, or PSI. The number actually on your tires, however, is not usually the ideal pressure. Rather, it is the maximum pressure that can be safely used, which is normally quite a bit higher than your ideal.

Each car has an ideal tire pressure suggested by the manufacturer. If you check your owner’s manual, it should list the appropriate pressure for your exact model of car. If you don’t have an owner’s manual, or if your owner’s manual doesn’t have this information, check inside the driver’s side door jamb. A sticker is usually affixed to this part of the door that includes all sorts of information about your car, including the recommended ideal pressure. For most cars this is generally around 30 PSI (2.1 kg/cm).

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To get the best mileage out of your tires, you may want to actually go away from the manufacturer recommended ideal pressure. Although their recommendation will usually result in the smoothest possible ride, it may not result in the best cornering or the best mileage. To determine this ideal tire pressure, take the maximum listed on the walls of the tires themselves, and reduce this by around 10%. That will generally result in a pressure that will give you the most benefits for everyday driving. Of course, for longer trips, or when bearing a heavy load, you may want to increase the tire pressure closer to the maximum.

Maintaining an ideal tire pressure has both financial and environmental benefits, both of which have been touted a great deal in the past few years. For one thing, keeping an ideal pressure reduces the wear and tear on your tires, and in conjunction with regular rotation this keeps your tires fit for a maximum period of time. For another, it can increase your gas mileage dramatically. People on average see a gain of about 2 MPG (117L/100km), which can save the average driver anywhere from $50 US Dollars (USD) to $100 USD a year.

This can stack up quickly as the millions of drivers on the road start taking their tire pressure more quickly. For the price of a $10 USD pressure gauge, and a five minute test once a month, Americans could save an estimated 40 million gallons (151 million litres) of gasoline each day. In a world where people are constantly looking to save money and the environment, it’s an obvious step to take.

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Discuss this Article

anon937785
Post 9

I agree that it can be somewhat helpful for things like MPG and tire life, to raise the pressure a little over the placard recommendation, especially if running soft tires. But going much beyond what the engineers calculate can be of dubious value. With higher pressures come a smaller contact patch (potentially less reliable traction), more suspension wear, and less resistance to road shocks like pothole impacts. Undoubtedly this all varies by vehicle, weather, and to some extent the tire.

As a general rule, though, I run 4-5 PSI over placard. Much beyond that and things start getting harsh on many road surfaces (to me a signal of excess), and in reality the gains rapidly diminish. If I were to get crazier over small benefits, I'd just split the difference between the automaker recommendation and the cold pressure maximum on the tire. But pushing it closer to the max (unless the application calls for it) doesn't seem worth the possible drawbacks.

anon925466
Post 7

I think you have to bear in mind what sort of driving you do and giving advice without some caveats is potentially dangerous.

Firstly, South Africa is one of the countries with very high road death rate. One of the common problems is that the plated psi on the tyre is viewed as the correct pressure. This, combined with high summer temperatures and overloading, leads to some spectacularly high deadly accidents.

I can agree that there was a story going back a decade or so where a US car manufacturer softened the recommended pressure to a level unacceptable to the tyre manufacturer. I believe it was Michelin.

There is an element of truth then about manufacturers plating the recommended pressure to how they want the car to feel. Generally speaking though, most car manufacturers are sensible.

If you are driving out in a land with long flat roads, then it is a different game compared to driving in the Ozarks where grip may be your first priority.

I drive a sports car and I reckon Porsche pretty much must get it on the button, so I am not going to mess too much with their recommendations. What is true is that I prefer driving on winter tyres because they feel much more sure-footed in our rainy climate in the UK where temperatures top out in the high 70's normally.

clintflint
Post 6

@bythewell - You can use a tire pressure monitoring system to make sure your tires are at the right pressure. They often come with the car now, but if not you can get one installed.

I know there is a group of people who make a study out of using as little petrol as possible and they do all kinds of fiddly things with their tires, changing the pressure depending on terrain and so forth. These are the same people who will turn off the engine on every downhill stretch.

They probably get to a point where it's not about the pollution or the money, or even the safety, but about the challenge.

bythewell
Post 5

Seems there's quite a science to this kind of thing. I generally don't pay all that much attention to my tire pressure unless they obviously need air. I get my mechanic to deal with them most of the time, but I really ought to take more responsibility, particularly as it seems they can dangerous if they aren't looked after.

anon267670
Post 4

@PelesTears: depending on the diameter and width of your tires and rims and the average speed you are running, you can safely air-down to at least 15PSI. I run 35x12.5/17 MT's on 17x9 rims, rarely drive faster than 25 MPH off-road, and normally run 15psi off-road.

PelesTears
Post 3

@ GlassAxe- I have the same tires on my FJ. When I go off-road, I let the air out until the tire pressure guage reads 28 psi. Is this too low, or is this okay for rocky desert terrain? I feel like I get good contact and grip, but I worry that there is too little pressure in the tires.

GlassAxe
Post 2

@ GenevaMech- I can tell you how I determine what I set my tire pressure. I have an F-150 that runs 275/65/R18 Load E Terra Grapplers. My tires are rated around 3600 lbs. at 80 Psi. My truck has a curb weight of 5400 lbs. With two people and the extra equipment I have on my truck I do my calculations at 6100 lbs.

I divide this by four to get an approximation of the weight per tire 6100/4=1525 (it is actually more weight on the front and less on the rear, But I can adjust for this ratio later). I divide this number into the Max per tire to get a ratio 1525/3600=0.424. I round up to the nearest percentage and multiply the max Psi by this percentage to find my per-tire Psi 0.43x80=34.4. This is the minimum pressure I want my tires to be at for the load that my truck is hauling.

I then inflate my tires to this baseline and run them for a few days, slowly adding air until I have the handling characteristics that I want. I run my tires at 50 Psi in the front and 40 Psi in the rear and I get decent gas mileage and good handling characteristics for every day driving. Off road tire air pressure is a whole different story.

GenevaMech
Post 1

How do I determine the proper tire pressure for my truck? I just want to figure out what tire pressure I should run my tires at for highway driving with two adult passengers. Does anyone know a formula that I can use to determine this?

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