A Tire Pressure Monitoring System (TPMS) is a system of integrated tire stem sensors that detect and warn a driver that tire pressure has dropped to a potentially unsafe level. The TPMS symbol looks like an exclamation point in parentheses. It is designed to illuminate when the pressure in one or more of your tires is reduced by around 25%.

In this post, we will look at the common questions drivers have about tire pressure monitoring systems (TPMS).

When did vehicles start having TPMS?

TPMS systems became mandatory for new vehicles in the early 2000’s, however, European and American luxury cars had adopted the technology even earlier. In 2012, the National Highway Traffic Safety Administration conducted a study to evaluate the effectiveness of TPMS in Proper Tire Pressure Maintenance. The study showed that 23.1% of the vehicles without a TPMS had at least one severely underinflated tire, while only 11.8% of TPMS-equipped vehicles had an underinflated tire. Based on the study findings, the NHTSA estimates that in 2011 mandating TPMS saved $511 million in reduced fuel consumption resulting from properly inflated tires.

When does the TPMS light come on?

The TPMS light is part of the pressure monitoring system that involves pressure detector sensors that are connected to your actual tires. The sensors are attached to the portion of the tire stem that is on the inside of the tire. Each pressure detector has a battery and transmitter that relays information to the vehicle’s onboard computer. A TPMS warning light illuminates on the dashboard panel when pressure in any of the tires becomes too low. 

Can cold temperatures affect TPMS?

Tire pressure can decrease about 1 PSI (pounds per square inch) for every 10 degrees the temperature dips below normal. This is not due to air escaping, but instead because the air inside the tire is condensing and taking up less space. This condensing effect is temporary since driving causes the tire to heat up, thereby increasing the tire’s pressure. A reason the light may come on, which is unrelated to tire pressure, is a dead battery in the TPMS system.

Additionally, tires tend to lose about 1 PSI per month from seepage of air around the edge of the rim, and even through the tread. Together these factors can cause tire pressure to drop as much as 25 percent below the recommended level. The sensing transmitters inside your tires notice this and trigger your TPMS dash light. If your TPMS light comes on you may not have a problem. You may just need to check your air and bring your tires up to the right pressure.

When should I worry about my TPMS warning light?

If your TPMS light illuminates, your tires are below the proper air pressure. You should always figure out why since underinflated tires increase the chance of tire failure, compromise vehicle handling, create improper tire and tread wear, and result in poor gas mileage. See if the light goes off after driving for a while, and also check the pressure of your tires when the vehicle is still warm. If a TPMS warning light persists with no apparent cause, take your vehicle in for professional service and evaluation.

So, you need to replace a flat tire that cannot be repaired. That’s bad enough. But then the repair guy says that you really should replace all four of your tires. Do you really need to replace three tires that seem perfectly good, just because one bit the dust? In many cases there are several good reasons why you should replace all four tires, instead of just the one that went flat.

The reason most all-wheel drive vehicles manufacturers recommend that you replace all four tires at a time is because all four wheels should have the same rolling circumference. If the wheels are not uniform, abnormal drivetrain wear  can occur, resulting in costly problems down the road. 

All-wheel-drive systems are designed so that the differential and the computer work together to send the right amount of torque to each wheel to minimize slippage and maximize control. When one of the tires is a different size than the others because three tires are worn and one is brand new,  the computer will take an inaccurate reading and the differential will have to work excessively hard. This can eventually result in damage to the drivetrain.

Unless your tires are brand new, the wear on all of your tires means you should probably bite the bullet and buy a new set. Additional benefits you’ll gain with a full set of tires for replacement include a more comfortable ride and better safety. Uneven tires can result in road noise and a vehicle that handles improperly, affecting maneuverability, traction, and smoothness of the ride.

It is easy to take your tires for granted. If you are a driver who tends to neglect regular tire care, you may miss important signs that your tires are no longer in good shape. The condition of your tires has a direct effect on your vehicle’s performance and your safety on the road. Driving on bad tires is extremely dangerous, and you might not even know you are doing it. 

Signs of Tire Trouble

Signs of tire problems may begin with small cracks in the rubber on the surface and inside of the tire. Over time, the cracking accelerates, and eventually the steel belting in the tread detaches from the tire. Once this happens, the tire is bad and no longer safe. We cannot stop the aging that ultimately leads to bad tires, but hot temperatures, under inflation, and poor tire maintenance are known to speed up the aging process. 

How Long Should Your Tires Last?

According to Car and Driver, the general consensus is that “most tires should be inspected, if not replaced, at about six years” and definitely “swapped out after 10 years, regardless of how much tread they have left.”

How to Determine a Tire’s Age

The U.S. Department of Transportation requires a DOT number to be printed on the sidewall of every tire. Tires manufactured after 2000 will end in a four-digit code. The first two digits indicate the week the tire was manufactured. The second two digits identify the year.  If your tire ends in a three-digit code, it is over 20 years old and should definitely be replaced.

To learn more about your tires, the Tire Safety Group offers a free tire facts app. Available for Android and iPhone, the app enables you to get a free Tire Facts Report by entering the DOT code from your tire.  The report lets you know if a tire is old, defective, or has been the subject of a recall. The app shows you where to find the code on the tire and even includes a flashlight function to help you see the code clearly!

In terms of safety, there may not be a more important component on your vehicle than its tires. Tires have evolved significantly since the earliest types, which were designed primarily for utility. Now, tires are made from specially formulated rubber compounds and the tread is engineered to provide specific safety features.

The First Tires

The earliest wheels were simply a solid curved piece of wood. As Continental Tires describes, “… leather was added to soften the ride. As time progressed it became solid rubber which led to today’s tire–the pneumatic, or air inflated, radial tire.”

Charles Goodyear is credited in the 1800’s with the discovery of the vulcanization process used to transform sticky raw rubber to firm pliable material which makes rubber a perfect material for tires. Tires were fabricated from solid vulcanized rubber until later in the century, when John Boyd Dunlop developed the popular pneumatic tire.

From that point, tire design gradually became more and more sophisticated with the development of bias ply tires and radial tires.

The Significance of Tire Tread

Tire tread is another important development in tire evolution. The tire tread is the part of the tire that actually meets the road. The elements of tire tread include tread blocks or tread lugs, tread grooves, tread voids, wear bar, and any extra features such as a rain grooves and siping. Tire tread spans the entire surface of the tire from shoulder to shoulder where the tread approaches the sidewall.

The areas between the tread blocks are referred to as the tread voids or tread grooves. Tread voids provide the tire with traction by enabling the tread blocks to move and flex as the tires to grip the road. They also allow the water to escape when roadways are wet. Tires with a high tread to void ratio provide better wet traction and braking ability.

Just as vehicles are engineered with a particular type of performance in mind, there are specific tread types and patterns that match each kind of intended performance. Tire tread is helps vehicles to corner tighter, accelerate more smoothly, and brake reliably. Tire tread is also capable of helping to maximize fuel economy.

Now that you know a little more about the importance of tire tread, you will understand why proper tire tread maintenance is so critical. In our next post, we will take a closer look at the best ways to maintain your tires and tire tread.