Best Tire Pressures for OEM & Aftermarket Wheels & Tires

Checking tire pressures

It just requires a good tire gauge, a scheduled reminder, and knowing the appropriate tire pressures for your tire-wheel-car combination.
It just requires a good tire gauge, a scheduled reminder, and knowing the appropriate tire pressures for your tire-wheel-car combination. | Source

Alternate method

Orange Electronic P409S Retrofit Tire Pressure Monitoring System
Orange Electronic P409S Retrofit Tire Pressure Monitoring System

If your older vehicle does not have TPMS, you can add them for peace of mind and safety.

 

Non-OEM Rims and Tires

Automobile manufacturers typically specify tire pressures on the driver’s doorpost or on the glove compartment lid. Sometimes it’s in the owner’s manual, too, but not if the car could have been ordered with various wheel and tire packages.

That was a good starting point when the car was new. But it has become popular to change to aftermarket wheels and tires, usually of a non-OEM size. And even if the car has its original OEM wheels, owners will often fit different size tires, usually wider, low-profile tires.

Cars sold new in the U.S. since 2008 have a tire pressure monitoring sensor (TPMS) installed inside each tire. When it senses tire pressure drop by 25%, a signal alerts the driver. While this is designed with road safety in mind, it is primarily for those who do not monitor tire pressures on their own. A driver who is consistently measuring tire pressure will have noticed a gradual leak before that point and only see this signal in case of sudden loss of air.

Aftermarket TPMS systems are far more accurate and can also be installed on older cars. On my RV, I use the TST 507RV w/ Flow Through Sensors, which monitors and displays temperature as well as psi for each tire. It has a digital read-out for each tire in addition to an audible alarm. The alarm triggers (high, low and hot) are adjustable, and sensors are accurate to within ±1.5 psi, all of which are desirable features when using aftermarket wheels, tires or pressures.

When to check tire pressures?

I check tire pressures monthly on the first of the month. Sometimes I’ll catch a small leak that I never would have noticed otherwise. I do it first thing in the morning, before driving on them or letting the sun warm them up. If I need to add air, I exceed by 2–5 psi and then bleed them off the next morning. As temperatures rise during the spring, pressures will actually rise slightly and I might have to bleed off ½ psi or so each month. In the fall, the cool dense air occupies less volume and I find that I usually have to add a bit of air each month. Since every tire pressure gauge reads differently, I always use the same one.

VIAIR 85P Portable Air Compressor
VIAIR 85P Portable Air Compressor

It's so nice to carry my own air pump instead of relying on the gas station having air. (The "gauge" is intended to be merely approximate. Use a separate one after inflating.)

 

It is common for tire shops and other automotive service providers to top-off pressures at 30–32 psi as standard operating procedure. Most car owners don’t know what tire pressures should be for their car and 30–32 is generally better than what rolls in for inspection. I have even seen an otherwise highly reputable frame and alignment shop routinely send out every vehicle with tire pressures set at what is marked as maximum on the tire sidewall!

Accutire MS-4350B Setpoint Tire Gauge
Accutire MS-4350B Setpoint Tire Gauge

My daughter finds this easier to use than pencil-type gauges. Her fingers are delicate, but she can grab this with both hands if necessary.

 

The Dynamics of Tire Grip

There are several objectives in setting the correct tire pressure, but the primary one is maximizing the tire contact patch. The contact patch is the somewhat squarish oval area of the tire that flattens in contact with the road at any given point. That is where the tire grips the road to achieve traction for braking, acceleration and lateral G-forces.

When tire pressures are too high, the tire balloons, increasing slightly in diameter and reducing the contact patch in both length and width. When tire pressures are too low—think of a flat tire—the contact patch is larger, but the increased sidewall flex produces damaging heat. Your car’s owner’s manual undoubtedly points out that tire pressures either too high or too low can ruin tires or cause problems even more serious and dangerous.

But what is that optimum tire pressure? The manual probably doesn’t specify, and certainly not for non-OEM size, aftermarket tires and wheels.

Start with what's posted on the door jamb

OEM tire pressures are usually posted on the driver's door jamb. This one suggests 32 psi for a stock 205x50R16 tire. I use a piece of drywall for chalk and a good quality tire gauge.
OEM tire pressures are usually posted on the driver's door jamb. This one suggests 32 psi for a stock 205x50R16 tire. I use a piece of drywall for chalk and a good quality tire gauge. | Source

What’s the Optimum Tire Pressure?

The method I use to determine the optimum tire pressure setting uses a piece of chalk or drywall. It also requires a tire pressure gauge and access to an air source near where you can drive your car on curves at a safe, but not pokey speed. A straight road won’t test adequately, and sharp turns at intersections are inaccurate. I used an empty lot where I could drive about 20 mph in a 10- to 15-yard radius. Tire pressures should be equalized at whatever you think is a good starting point. The car should not have unusual loading—leave the teens home unless you’ve always got a carload of them!

Make three chalk marks on the shoulder, including some tread and some sidewall.
Make three chalk marks on the shoulder, including some tread and some sidewall. | Source

This is a standard procedure for autocrossers who usually want to run different tire pressures when racing than for street use.

Mark the tire with chalk

With your chalk, make three equidistant marks on the shoulder of each tire (or at least one front and one rear tire). The mark should go far enough onto the sidewall that it will extend past what the tire should ever drive on. It should extend onto the tread far enough that you expect that part to contact the road with every rotation. Three marks will enable you to see at least two of them no matter how the wheel rolls to a stop.

Tire pressures set 5 psi high

Click thumbnail to view full-size
The inner front tire is lightly loaded when turning away from it. The outer fourth of the tread isn't touching the pavement enough to scrub off the chalk!The inner rear tire shows wear similar to the front. If it were not overinflated, more of the tread would contact the road.The outer front tire has more weight on it as the car leans and, therefore, uses the entire tread width, even when overinflated by 5 psi.The outer rear tire is not scuffing as far around the shoulder as the front is. I should either run a bit less pressure in the rear or more in the front.
The inner front tire is lightly loaded when turning away from it. The outer fourth of the tread isn't touching the pavement enough to scrub off the chalk!
The inner front tire is lightly loaded when turning away from it. The outer fourth of the tread isn't touching the pavement enough to scrub off the chalk! | Source
The inner rear tire shows wear similar to the front. If it were not overinflated, more of the tread would contact the road.
The inner rear tire shows wear similar to the front. If it were not overinflated, more of the tread would contact the road. | Source
The outer front tire has more weight on it as the car leans and, therefore, uses the entire tread width, even when overinflated by 5 psi.
The outer front tire has more weight on it as the car leans and, therefore, uses the entire tread width, even when overinflated by 5 psi. | Source
The outer rear tire is not scuffing as far around the shoulder as the front is. I should either run a bit less pressure in the rear or more in the front.
The outer rear tire is not scuffing as far around the shoulder as the front is. I should either run a bit less pressure in the rear or more in the front. | Source

Tire pressures set 5 psi low

Click thumbnail to view full-size
The outer front tire has scuffed all of the shoulder grooves, and the car wasn't even leaning. It needs more air.The outer rear tire is scuffing too much, but not as bad as the front. I should add an extra 1-2 psi to the front.The inner front tire is loaded so lightly when turning this direction that one fourth of the tread width is still chalked.The inner rear tire shows wear similar to the front. But if the outer tires are scuffing the shoulder, then the pressures should be raised.
The outer front tire has scuffed all of the shoulder grooves, and the car wasn't even leaning. It needs more air.
The outer front tire has scuffed all of the shoulder grooves, and the car wasn't even leaning. It needs more air. | Source
The outer rear tire is scuffing too much, but not as bad as the front. I should add an extra 1-2 psi to the front.
The outer rear tire is scuffing too much, but not as bad as the front. I should add an extra 1-2 psi to the front. | Source
The inner front tire is loaded so lightly when turning this direction that one fourth of the tread width is still chalked.
The inner front tire is loaded so lightly when turning this direction that one fourth of the tread width is still chalked. | Source
The inner rear tire shows wear similar to the front. But if the outer tires are scuffing the shoulder, then the pressures should be raised.
The inner rear tire shows wear similar to the front. But if the outer tires are scuffing the shoulder, then the pressures should be raised. | Source

Straight-line test drive

Now take a short test drive. A couple hundred yards should be enough to wear off some chalk. For this first test, just drive straight, no curves or turns. Park the car at a safe location and examine the chalk marks. Ideally, chalk should have worn off the entire tread width, but not the shoulder. If chalk is worn off partway onto the shoulder of the tire, add about 4 psi and retest. But if there’s still chalk at the outside edge of the tread, bleed off about 2 psi and try it again. There will probably be a range of about 3–4 psi that passes this test, and it’s better to be on the high side than low.

Test drive on curves

Now refresh the chalk marks and do a second test. For this one, you might need a quarter mile of curvy road if you can't find an empty parking lot. Just make sure to include sweeping left- and right-hand curves. Take the curves at a normal everyday speed. Don’t go slowly like you’re trying to keep a cup of coffee from spilling into your lap. And don’t go squealing the tires—unless you drive like that all the time—and I hope you don’t.

Park the car again and examine the chalk marks. Ideally, chalk should have worn very slightly off the shoulder as the tire flexed through the curves. If too much is scrubbed off, and you don’t want to be driving that much on that part of the shoulder, then add about 2 psi. Retest it to see if that looks better, but also redo the straight-line test to make sure that the entire tread width is still in contact with the road.

Optional fine tuning—Really optimal

Ultimately, you will probably find a range of about 2–3 psi that gives best traction without undue sidewall flex. Now, if you want to get really picky, you can adjust up or down 1–2 psi for fuel efficiency or ride comfort. Just be aware of the trade-offs discussed below and keep the full tread width in contact with the road.

Tire pressure quiz

(These chalk marks may be misleading; look at the tire itself for the quiz below.)
(These chalk marks may be misleading; look at the tire itself for the quiz below.) | Source

Is there a difference above?

Surprising results for my car!

My 1981 Celica specifies 24 psi. That sounds quite low; they just don’t make cars like that anymore. Therefore, shops that routinely inflate to 32 psi are way off. Through the testing described here, I find that 24 psi is, indeed, ideal for the rear, but that 31 psi is best for the front. I could probably lower that some if I didn't drive it so hard.

Factors that Affect Tire Adhesion

I have already alluded to some factors that affect tire adhesion. There are two aspects to the contact patch: length and width. Beyond that, tire pressures can be adjusted to compensate for vehicle loading and other minor factors.

Tread width and wheel width affect width of contact patch

A tire with a wider tread width has a wider contact patch. Conversely, a narrower tread width gives a narrower contact patch. (Wider is not always better, but that’s beyond the scope of this article.)

The effect of wheel width is something that is less obvious. When the wheel is too narrow for the tire, the tread does not contact the road at the edges close to the shoulder. Conversely, a wheel that is too wide will give the tire a tendency to roll-over onto the shoulder. In practice, this has little effect except close to the specified minimum or maximum wheel width for a given tire size—or for very aggressive driving where the tire “leans over” in relation to the wheel.

Gross vehicle weight (GVW) affects tire grip

A heavier load places more weight on the tire, causing the sidewalls to deflect more. Deflecting the sidewalls creates heat, just as when a tire is under-inflated. In fact, when carrying heavier loads long distances, tire pressures should be increased slightly. Just stay within the specified load capacity of the vehicle and tires. How much air should be added? Use the chalk method if there is any doubt!

Other factors

If you’re still with me, your eyes are probably starting to glaze over, so I’ll just mention several other factors briefly.

A spirited or aggressive driving style will generally warrant somewhat higher tire pressures than a sedate conservative style. Higher tire pressures will keep the tires from rolling-over and flexing so much when subject to lateral G-forces.

Somewhat related to driving style is the temperature of the tread. Rough driving heats up the tread. So does driving on pavement baked by 100° ambient temperatures (the paved surface is a lot hotter than that). Either way, heat beyond a certain point will weaken the rubber tire compound enough to dislodge small chunks under severe braking or cornering. Higher tire pressures will reduce heat build-up.

How often do you check tire pressures?

See results without voting

The stickiness of the tire compound affects grip. Generally, tires with longer mileage warranties are made from harder tire compounds that may not have as much grip as those that are softer. It’s a trade-off. Really sticky race tires, for example, get lousy mileage, but grip the pavement, which is what they are designed to do. Higher tire pressures will reduce heat build-up.

The coefficient of friction is different for each road surface. Concrete has more grip than asphalt. Obviously, hard dry surfaces have more grip than dirt, gravel, sand, wet surfaces, standing water, snow and ice. Tire pressures can be optimized for any of these surfaces if that’s where the tires will primarily be driven. On the non-hard surfaces listed here, tread pattern affects grip as well.

Essential auto safety accessories

Kidde 466727 Halotron Fire Extinguisher, 2-1/2-Pound, 2BC
Kidde 466727 Halotron Fire Extinguisher, 2-1/2-Pound, 2BC

Filled with halotron gas, so there's no foam to clean up afterwards like with the cheaper extinguishers. (Believe me, and don't ask how I know!)

 
Jump-N-Carry JNC300XL 900 Peak Amp Ultraportable 12V Jump Starter with Light
Jump-N-Carry JNC300XL 900 Peak Amp Ultraportable 12V Jump Starter with Light

When your battery is weak and there's nobody else around--well, it's just good to be prepared and independent.

 
Coleman Cable 08471 12-Feet Medium-Duty Booster Cable with Non-Polar Glow Clamps, 8-Gauge
Coleman Cable 08471 12-Feet Medium-Duty Booster Cable with Non-Polar Glow Clamps, 8-Gauge

These battery booster cables are good for jump-starting cars and light trucks. If you've got a really big engine, I'd recommend 6- or even 4-gauge instead.

 

In conclusion, test your car with the tires and wheels you use and determine the optimum tire pressures for your personal driving style. Then check and adjust tire pressures frequently—I do it monthly. Your car will have better handling, braking, and fuel mileage. Your tires will last longer. And you will be happier.

More by this Author


If you found this article helpful, please tell others why. 13 comments

johnmarsh098 profile image

johnmarsh098 4 years ago from New York, Smithtown

Great Informative hubs ! Never know you have to be so careful about Tyre pressure and surprise to know about different test drive methods and Tire Adhesion...Nice Job..


livingpah2004 profile image

livingpah2004 4 years ago from USA

Congrats on HOTD!


urmilashukla23 profile image

urmilashukla23 4 years ago from Rancho Cucamonga,CA, USA

Useful Hub. Thanks for posting it.

Congratulations on Hub of the day award!


Denise Handlon profile image

Denise Handlon 4 years ago from North Carolina

Howard-congratulations! Your car maintenance hub was picked for Hub of the Day. Good going. :)


Howard S. profile image

Howard S. 4 years ago from Dallas, Texas, and Asia Author

@ktrapp: The attribute "ingenious" makes me feel good. Thanks. I could say I was inspired by your soup-can math hubs, but I don't think you'd believe that. What I think you might believe, however, is that I was inspired by your explicit instructions on how to merit Hub of the Day. HoD compensates psychologically for being gagged by Google.


Howard S. profile image

Howard S. 4 years ago from Dallas, Texas, and Asia Author

@a2aoptima, yes, I am definitely the how-to DIY type, and approach everything analytically. You will never catch me (I hope) writing an article about how to do something ordinary unless I have a very unusual angle on it.


Howard S. profile image

Howard S. 4 years ago from Dallas, Texas, and Asia Author

@Denise, thanks for the encouragement. BTW, your brake pad hub reminded me that I'm supposed to do the front brakes on my wife's car sometime soon. That's something I've never done, although I know how (I think). I've bled brakes numerous times though, and changed a couple of brake master cylinders.


lovesleftovers profile image

lovesleftovers 4 years ago from Texas

Great, informative hub! I used to work in the automotive department at a major retailer and was always surprised by how many customers paid very little attention to the condition of their tires. Voted up, interesting and useful :)


a2aoptima profile image

a2aoptima 4 years ago from Bangalore, Karnataka

Howard, you are a real & practical scientist. The experiment with chalks was awesome. Nice inputs that will really be helpful to people.

Great hub, and congrats on winning the HOD.


ktrapp profile image

ktrapp 4 years ago from Illinois

What a thorough hub on tire pressure. The chalk method you describe for figuring optimum tire pressure is ingenious. This is all a good reminder to me, as well, that I need to have the tire pressure checked on both of our car; I think it's been awhile. Great hub and many congratulations on being Hub of the Day.


Denise Handlon profile image

Denise Handlon 4 years ago from North Carolina

Excellent hub, Howard. Very thorough info here. Thanks for sharing. I voted it Up/useful and interesting.


MarleneB profile image

MarleneB 4 years ago from Northern California, USA

I am sure the average person like me is blown away by the amount of information there is to know about tires. My husband is a "spirited" driver. So, now I can intelligently ask him if he inflates the tires to accommodate his style of driving. He'll get a kick out of it. I really enjoyed this hub. It's filled with valuable information.


Simone Smith profile image

Simone Smith 4 years ago from San Francisco

I can safely said that this is the most information on car tires that I hav ever been exposed to. What a useful Hub! I've learned a lot of practical things- and interesting details to boot! I hadn't realized that tire pressure monitoring sensors existed, for example. How cool are those! Thanks for the great Hub, Howard S!

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