A Caution Concerning Tires and Extreme Heat

We have discussed the effects of cold weather on tires many times, but with the record-breaking heatwave across Europe and in parts of the US, we thought it would be an excellent time to discuss the effect of extreme heat on tires and vehicle control.

Basic Tires
The only connection between you and mother earth are your tires. Keep in mind that the tires don’t support the vehicle load. The pressurized air inside the tire supports the weight of the vehicle. The tire is just the container; this might sound obvious, but it is critical to understand.

Heat and Tires
Tire pressure will increase as the outside air temperature rises, tire pressure will go up approximately one pound for every 10 degrees Fahrenheit. Tire pressures are a vehicle characteristic that needs monitoring often. The Tire Pressure Monitoring System will warn the driver when the tire pressures are low but do not supply a warning when the pressure is too high.

Excessive heat will over-inflate the tires. Over-inflated tires can lose traction because the shape of the tire becomes deformed by extreme air pressure, decreasing the tire’s footprint on the road, limiting traction and stability. The tires can be more prone to damage. An over-inflated tire is stiffer and can cause loss of control when they come in contact with common road hazards like potholes.

We suggest that you look at the Temperature letter on your tire. The temperature grades are an indication of a tire’s resistance to heat. Sustained high temperature (for example, driving long distances in hot weather), can cause a tire to deteriorate, leading to blowouts and tread separation.

Temperature Grade

An explanation of  Temperature (Resistance) Grades From the Tire Rack Website
The UTQG Temperature Grade indicates the extent to which heat is generated or dissipated by a tire. If the tire is unable to dissipate the heat effectively or if the tire is unable to resist the destructive effects of heat buildup, then its ability to run at high speeds is reduced. The temperature grade is given by measuring a loaded tire’s ability to operate at high speeds without failure by running an inflated test tire against a large diameter high-speed laboratory test wheel.

Temperature Grades Speeds in MPH:

  1. Over 115
  2. Between 100 to 115
  3. Between 85 to 100

The speeds may seem excessive, however, these tests are conducted with a driver and no extra load. An SUV with 3 to 4 passengers and luggage, or in a security situation, armor, creates a much different test scenario. I strongly suggest to always have A rated tires, plus daily evaluation of the tire pressures.

For additional information and resources click on the links below.

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