Telling Men From Boys - Tire Review Magazine

Telling Men From Boys

More than a few times, I’ve heard people explain that the basic difference between car tires and truck tires is their obvious relative size: truck tires are bigger!

This fact is certainly true in the majority of cases, but even that explanation is becoming a bit marginal. While overall outside diameters remain quite different (at least today), wheel diameter sizes are another story. With 20-inch and 22-inch tire and wheel packages becoming more common on cars and SUVs, that size gap has all but closed. And, with 24-inch to 30-inch tires and wheels finding more applications, wheel diameter is no longer a defining trait of medium truck tires.

Two opposing trends are blurring some of the traditional distinctions between these tires. On the passenger side, styling and performance are the primary motivations behind monstrous tire/wheel packages.

Then, on the truck tire side, high load capacity 15-inch and 16-inch commercial tires are rapidly gaining in popularity, especially on parcel delivery and local distribution trucks. These small, heavy-duty tires allow for truck bodies with greater cube capacity, and, therefore, improved productivity.

Let’s look closer at some of the distinctions that clearly differentiate car and truck tires.

Load Capacity

Load and inflation ratings are the most basic engineering parameters that relate to the duty cycle capabilities of tires. For passenger car tires (P-metrics), the mandatory sidewall stamping typically reads "Maximum Load X lbs. @ Y psi Maximum Inflation Pressure." Truck tires, on the other hand, are typically marked "Maximum Load X lbs. @ Y psi." The difference is subtle but very significant, and the following points should be noted:

®€′ For passenger tires, maximum load capacity and maximum cold inflation pressure limits are always stated on the sidewall and clearly relate to one another. They should not be exceeded. Load adjustments may also be required for applications with certain tire service or vehicle speed combinations.

®€′ For truck tires, only the maximum load capacity is stated. The cold inflation pressure stated is simply the minimum acceptable pressure corresponding to that maximum load at normal highway speeds. It is not a maximum value and should, in fact, be adjusted in accordance with tiremaker recommendations for different operating conditions. Speed, axle position, wear patterns and maintenance practices are typical variables considered when setting inflation pressures.

The inflation pressure details on tire sidewalls are informative. However, they are not necessarily the same as application-specific inflation pressures recommended for individual service conditions.

For all vehicle types, operators should first follow specific inflation recommendations and load restrictions given by the vehicle manufacturer, provided there is no conflict with any recommendations from the tire manufacturer or with tire industry standards.

For clarification of industry standards, contact the Tire and Rim Association ( or the Rubber Manufacturers Association (

In all cases, inflation recommendations, including those stated as "maximum," are cold pressure values (measured with tires at ambient temperatures) and do not include any pressure build-up due to vehicle operation. It is not unusual for passenger tire inflations to increase from 2 psi to 5 psi, and larger medium commercial truck tire inflations to increase from 5 psi to 15 psi, due to heat generated by normal highway service.

Inflation Pressures

Inflation pressures, as well as loads, can significantly affect vehicle handling and stability. This is more evident in passenger cars and other light duty applications, as tires on these vehicles are usually designed to operate at lower inflation pressures than truck tires. Typical passenger tire pressures range from approximately 26 psi to 41 psi, compared to large, over-the-road truck tires that operate in the 100-psi range.

An underinflation of 5 psi, for example, would represent 17% underinflation of a tire with a 30-psi target, compared to just a 5% underinflation of a tire with a 100-psi target. Some passenger and light truck vehicles also specify different inflation pressures for front and rear axles. This may be to allow for vehicle loading and/or weight distribution, but may also relate to vehicle handling/stability.

If P-metric tires are used in light truck, SUV, trailer, or multipurpose passenger vehicle applications, a load service factor of 1.10 applies. This means that the passenger tire selected must be rated to carry at least 10% more load than if it were being used on a traditional passenger car. Practically, this results in fitting tires that are at least one size larger to these vehicles.

Truck tires, on the other hand, are designed with higher center-of-gravity loadings expected and do not require this kind of size or load rating adjustment when fitting a tire to a vehicle.

Another caution applies to vehicles subject to asymmetric loading, such as those equipped with heavy on-board servicing or loading/unloading equipment. Some large RVs also fall in this category, with holding tanks, extra fuel tanks, air conditioning units, etc. installed on one side of the chassis.

Tire inflation pressures for such applications should cover the heaviest loaded wheel position across each axle. This can only be determined by weighing each axle end. Therefore, when determining target inflation pressures for these vehicles, one cannot simply weigh the axle and divide that load equally among the tires across the axle.

The Maintenance Factor

The observations above deal with "target" inflation pressures and loading. In real-world service, of course, tire care and maintenance practices influence actual tire operating inflation pressures and, in turn, tire performance.

One primary function of periodic inflation pressure checks and fleet surveys should be to quantify the effectiveness of routine maintenance programs. Generally, longer intervals between tire service/maintenance should relate to higher tire reserve load capacity. Since tire load carrying capability at any given inflation is fixed by design, this translates to some increase in target inflation pressures for fleets with longer intervals between checks, within guidelines endorsed by tire suppliers.

Surely, the basic size and construction features of car and medium truck tires are enough to tell them apart. It’s doubtful, though not impossible, that they will ever reach a point of being nearly identical in every conceivable way.

As fleets continue to reach for every cent of profit and consumer tastes evolve, who knows in what direction tire designs will head?

Perhaps in the distant future, all Class 1 through 8 vehicles will ride on super ultra-high performance, asymmetric Z-rated 11R28.5s. At least for today, though, the true differences between the two go far deeper than just size.

You May Also Like

EVs, Fleet Management to Aid Commercial Tire Growth

The post-COVID market is bouncing back, which will drive market trends in 2023.


When I was a child, rollercoasters were an awe-inspiring combination of power and adrenaline, a towering marvel of speed and terror to be gazed upon with either great anticipation or great fear– sometimes both. I have always loved knowing how things work, and even at a young age, I appreciated the mechanics of it all: the slow, steady, deliberate creaking of the steep climb, and the unseen forces just out of reach methodically pulling riders toward the unknown.

Last-Mile Delivery Tires Set to Outpace Long-Haul Tire Volumes

Prior to the pandemic, the last-mile delivery (LMD) market was booming. So, when COVID-19 hit, and newly-homebound consumers placed even more online orders — retailers like Amazon shortened delivery times to two days, one day, or even same-day services — and the segment exploded. Related Articles – Goodyear Unveils 90% Sustainable Tire – Goodyear Introduces

Global Tire Manufacturer Ralson Enters US TBR Market

Global tire manufacturer Ralson is entering the U.S. commercial tire market with a new medium/heavy truck tire manufacturing facility and a team of veteran American sales and marketing tire professionals. Ralson debuted its products for the US with its American team at the 2022 SEMA Show in Las Vegas. Related Articles – Maxam Tire Completes

Michelin Releases Agilis HD Z as New Urban and Regional Tire

Michelin North America has released the Michelin Agilis HD Z 19.5 in two sizes to offer fleets with light and medium-duty vehicles durable, long-lasting tires optimized for the stresses of urban and regional environments. The Agilis HD Z 19.5-in. tires will replace the Michelin XZE in two current sizes (225/70R19.5 LRG and 245/70R19.5 LRH) in

Yokohama Tire Launches the 716U UWB Regional Drive Tire

Yokohama Tire’s newest commercial tire – the 716U ultra wide-base – is a weight-savings drive tire that carries more profitability for fleets, the company says. It is available now in the US in size 455/55R225. Related Articles – BKT Highlights Ridemax Radial Floatation Tire for AG, Tank Trucks and Spreaders – CEAT Specialty Tires Increases


Other Posts

Vredestein Launches New Pinza H/T in US

Vredestein Tires has launched its new Pinza H/T line of tires, a highway all-season tire designed for trucks, SUVs and crossovers. According to Vredestein, The Pinza H/T has unique features that keep the comfort of the driver in mind. Related Articles – Goodyear Adds Wrangler HT Tire to Light Truck Lineup – Comparing Trends in

Vredestein Pinza H_T
Goodyear Adds Wrangler HT Tire to Light Truck Lineup

The Goodyear Tire & Rubber Company has added the Goodyear Wrangler Workhorse HT to its Wrangler light truck tire lineup. Goodyear says its Wrangler Workhorse HT provides all-season traction, a confident ride and the strength to go the extra mile. Related Articles – BKT Tires Launches Agrimaxfactor Tire For Tractors – Michelin’s Enviro System Unveils

Comparing Trends in All-Season and All-Weather Tire Segments

When it comes to all-season and all-weather tires, consumer expectations have been a driving force in both segments, affecting everything from OE fitments and sales trends to tire performance. Essentially, consumers want the convenience of not having to swap tires every winter, as well as the safety and performance provided by capable all-weather tires, according

All season all weather vredestein hypertrac
Continental Debuts Enthusiast-Driven ExtremeContact Sport 02

From timed autocross laps to drifting on a skid pad and mastering knee-jerk braking and turns on a raceway, dealers, influencers and members of the media were treated to a crash course in performance racing while testing out Continental’s newest UHP summer tire, the ExtremeContact Sport 02. Related Articles – Mickey Thompson Unveils 42-, 44-in.