Understanding TPMS (Tire Pressure Monitoring System)

If you own a vehicle made after 2007, you’re already the proud owner of TPMS, a.k.a. Tire Pressure Monitoring System. These systems became a legal requirement in all vehicles sold in the United States in 2007, though some earlier models of vehicles were already equipped with them. Since they affect almost everyone nowadays, let’s take a look at what they do and how they work. 

 

TPMS is a system designed to let you know when your tires are low on air. In theory, you’ll be alerted once a tire loses at least 25% of its air required air pressure. The overarching idea is, of course, to increase safety while driving. Most people can tell when their tire is totally flat, but getting a warning before you’re stranded somewhere can not only help you get to safety in time, but also helps maintain the integrity of the tire. Perhaps the damage can be fixed if it’s caught early on; or, maybe you haven’t filled your tires up in a while and they’re just low on air. Either way, driving on under-inflated tires can be a safety hazard, and can significantly reduce the life of your tires. When your tires are low enough on air to set off the TPMS, you’ll see the symbol to the right light up on your dashboard. Some vehicles will tell you which tire is low, and some just alert you to the problem while you’re left to determine which tire is the culprit. 

There are 2 different types of TPMS, and they each have their strengths and weaknesses:

Direct TPMS – Each tire has a dedicated sensor installed within the tire and connected to the valve stem. These sensors take air pressure readings and send the data to your vehicle’s dashboard. 

Pros – They deliver accurate pressure readings; batteries can last up to 10 years; there is no need to reset them after tire rotation or inflation adjustments.

Cons – They are more expensive to maintain (if/when sensors need to be replaced); sensors can be damaged during tire installation if the techs aren’t careful; they require costly tools to maintain them (which your auto shops will have); the large variety of proprietary sensors can make it a challenge to find the right one for your specific vehicle. 

Indirect TPMS – This system uses the vehicle’s ABS (anti-lock brake system) to approximate air pressure based on tire rotation speed. If one tire is spinning at a different rate than the others, it can indicate underinflation. 

Pros – It’s less expensive since it doesn’t use sensors; it should last the life of the vehicle.

Cons – The readings may be inaccurate if you change tire size or the tires are worn unevenly; if all 4 tires are equally underinflated due to neglect, they won’t spin at different rates, and you may not be alerted to a problem despite all tires being underinflated; the system must be reset after tire rotations and inflation adjustments (meaning drivers often have to do this themselves, rather than leaving it up to auto techs); you may have to drive considerable distance before this system will detect a problem, unlike sensors that read air pressure immediately.

Do you know what kind of TPMS your vehicle uses? If you’re unsure, you can check your vehicle owner’s manual, or simply ask your auto technician the next time your vehicle is being serviced. While both of these methods will help alert you to a problem, one of the best ways to maintain your tire pressure is to simply check it regularly! We recommend monthly air pressure checks, along with a check once the weather gets cold (as this will make your tire pressure drop). Tire pressure gauges are inexpensive, small, and easy to use; they are a great tool to keep in your glove box or trunk at all times. At Wiygul Automotive Clinic, we’re dedicated to keeping you safe on the road! Our tire experts will happily inspect your tires and assist you with your TPMS anytime.