The Heat Is On!

Extreme summer temperatures can add stress to commercial tires, making preventive maintenance and pressure monitoring critical for fleet safety.

For Canadian fleets, summer heat waves are a growing concern. Prolonged periods of high temperatures can affect tire pressure, operating temperatures, tread wear and vehicle safety. While modern commercial tires are engineered to handle a broad range of conditions, extreme heat makes proper maintenance more important than ever.

The good news is that fleets do not necessarily need special tires simply because temperatures are rising. However, heat can magnify problems that may already exist, particularly underinflation, overloading, irregular wear or damage, which is why added vigilance is a must.

Heat starts inside the tire

The relationship between load and heat is fundamental to understanding summer tire maintenance. Chris Queen, Technology Director, North America Commercial at Goodyear explains that, “as a tire carries load, it flexes as it moves through the footprint, and that flexing naturally generates heat.”

This heat is influenced by more than just the thermometer outside. According to Queen, “the amount of heat a tire experiences is influenced by multiple operating factors, including load, inflation pressure, speed, road surface conditions, and ambient temperatures.”

For heavily loaded commercial vehicles, therefore, heat waves can create a particularly demanding operating environment. Fleets need to consider the combined effect of vehicle weight, tire pressure, speed and pavement temperature rather than treating ambient temperature as the only factor.

Queen emphasizes that maintaining “proper inflation, distributing loads appropriately, and operating within tire load ratings” helps tires perform as designed.

Fleets should not assume that a 40°C day is automatically dangerous for commercial tires.

Pressure remains critical

The most important maintenance issue during a heat wave is inflation pressure. Russell Shepherd, Michelin Director of Technical Communications says, “as the air becomes hotter in a tire, the air pressure increases.” That does not mean fleets should release air from a hot tire. Instead, pressure should be set correctly when the tire is cold.

Shepherd defines “cold” as, “whatever the air temperature in the tire is before you drive, or at least three hours after a drive.” Establishing the correct cold inflation pressure is important because, “the proper inflation pressure cold (not driven) assures the optimal inflation pressure once you are on the road.”

Shepherd says a 5°C temperature change can affect inflation pressure by 1-2 psi. Although normal morning-to-afternoon changes are generally not a major concern, seasonal temperature changes can be much more significant.

That’s why Shepherd recommends checking tire pressure at least monthly, and before road trips, with adjustments made when tires are cold.

Underinflation is the bigger concern

Although the increase in pressure that accompanies rising temperatures is an issue to keep in mind, underinflation is a more fundamental tire-maintenance concern. “Underinflation of a tire can contribute to irregular tire wear and, if low enough, tire failure, regardless of the temperature,” Shepherd explains.

Goodyear's Queen similarly stresses the importance of routine pressure monitoring. “Tire pressure plays a critical role in tire performance,” he says, adding that routine pressure monitoring should be part of every preventive maintenance program.

For fleets operating during extended heat waves, that means making tire pressure checks a priority, rather than relying exclusively on scheduled maintenance intervals.

Technology can also help. Queen points to systems such as Goodyear TPMS Plus, which can provide “continuous digital monitoring of tire pressure and temperature,” allowing fleets to identify developing problems before they result in catastrophic failure.

Inspect for more than pressure

Pressure is only one part of the equation. Queen recommends regular inspections to identify, “irregular wear, damage, or other service-related concerns, and to verify that tires are properly inflated and operating within recommended load limits.”

Drivers should also pay attention to how a vehicle feels on the road. Shepherd identifies vibrations from one or more wheel positions as, “a clear indication of a problem with the tire or wheel.” This makes driver feedback an important part of a fleet's tire-management program.

Heat can also affect tire materials. Shepherd explains that, “rubber compounds are typically the most sensitive to variations in heat conditions.” Temperature can affect rubber properties, including how hard the compound becomes and its adherence to the road surface.

Today's tires are designed for heat

Fleets should not assume that a 30°C or 40°C day is automatically dangerous for commercial tires. Shepherd notes that Michelin uses testing and computer simulations, “to ensure designs are prepared for the extremes of summer in North America.” He stresses that the same tires used in Canada can operate safely in the hottest parts of the United States.

Goodyear takes a similar position. Queen says commercial truck tires, including long-haul, retreaded and all-weather products, are “engineered and tested to perform across a wide range of operating conditions.”

Don't overlook seasonal tire selection

While commercial fleets generally run tires designed for year-round operating conditions, the issue of tire selection is particularly relevant to fleets operating passenger cars, SUVs and lighter-duty vehicles.

Michelin and Continental both caution against leaving winter tires on vehicles through the summer.

Michelin points out that winter tires are optimized for conditions below 7°C, providing better traction and shorter stopping distances in snow, ice, slush and freezing conditions. In hot temperatures, however, “performances such as wet braking are significantly reduced.”

Continental stresses that winter tires are designed with specialized rubber compounds that remain flexible in cold temperatures. On hot summer days, however, “the softer tread of a winter tire wears out a lot quicker on warm tarmac.”

How much quicker? According to Continental, running winter tires year-round can reduce their service life “by as much as 60%.”

Continental also notes that winter tires on warm pavement can increase rolling resistance and fuel consumption. More importantly, their softer tread can compromise handling during emergency manoeuvres and increase stopping distances.

A heat-wave maintenance checklist

Despite the hotter weather, tire manufacturers assure fleet professionals that there’s no need to reinvent their tire-maintenance programs.

Stick to the basics: Check inflation pressures when tires are “cold,” and ensure loads remain within rated limits. Fleets should also conduct regular visual inspections for damage, irregular wear and other issues.

For larger fleets, continuous tire-pressure and temperature monitoring can provide an additional layer of protection and help identify problems before they become roadside failures.

The good news is that modern commercial tires are capable of handling demanding summer conditions, including heat waves. However, they cannot compensate indefinitely for underinflation, overloading, damage or neglected maintenance.