If you’ve been in a tire shop, you’ve heard all the usual advice about tire pressures. Keep your tires inflates so they last longer and get better fuel economy, but there is more at stake. Tires are the most critical component on your vehicle. They grip the road and provide the traction you need to start, steer and stop your car. When one of them fails, your vehicle is impossible to control.
To combat these problems, tire pressure-monitoring systems (TPMS) became mandatory on all new passenger vehicles sold in the United States starting in 2007. These tire air level sensors alert drivers when their tires lose air. While these TMPS devices work, they also require maintenance and are not always foolproof.
1. Tire Pressures Have a Mind of Their Own
You may not be aware of it, but your tire pressures change all the time. Flex in the sidewalls while cornering or going over bumps in the road allow minuscule amounts of air to escape. You lose as much as 1 PSI of pressure every month of driving.
Changes in the weather and operating conditions also affect tire pressures. Colder weather causes the air to contract, and pressures drop. In warm climates, heat increases the pressures.
There are two basic styles of tire pressure monitoring systems, and they have different advantages and disadvantages.
An indirect system depends on the antilock brake’s wheel speed sensors for inputs. It works like this:
• Speed sensors count the rotations of all four wheels
• Steering angle corrects for rotational differences around corners
• A computer estimates vehicle speed based on an average of inputs
• When one wheel turns slightly slower than another, the system indicates low tire pressure
Indirect systems might alert you to a sudden loss of tire pressure in one wheel, but that is all they do. It does little to track the performance of the entire set. All four tires may lose air at the same rate and become underinflated as a group.
A Direct TPMS transmits tire pressure and temperature data to a computer inside your vehicle. Here is how they work:
• A battery operated hydrostatic pressure gauge takes a reading of tire air pressure
• The information transmits by RF signal to antennas on your vehicle
• A computer interprets the data and displays the results on your dash
These are much more reliable, but problems with the antennas or weak batteries in the sensors throw off the results. Rotating tires also changes the readings, and your system must recalibrate.
These tire level sensors keep you better informed, but it is still essential to manually check your tire pressures. A broken hydrostatic sensor or improper maintenance leads to false conclusions and leave you vulnerable to other common tire-related problems.
2. Improper Tire Pressure Costs Money
Radial tires are the standard these days. A steel belt wraps around the outside carcass and forms a cylindrical shape. This shape is important. A tire works like a balloon. The air inside pushes out on the walls and gives it form. When inflated, the bands need to remain flatly stretched across the width of the tire.
With too much pressure, the bands distort. Overinflated tires bow outwardly across the tread pattern. This condition wears out the center of the tire quickly and causes bald spots.
Underinflated tires have the opposite problem. They bow inwardly. The shoulders of the tread hit the ground and wear quickly. This situation can also cause the body of the tire scrub along vulnerable areas.
Underinflated tires also tend to drag along the ground more. The higher rolling resistance increases the amount of energy necessary to move the vehicle, and it makes the engine work harder. With all four tires underinflated, the fuel economy might suffer as much at 3%.
3. Better Safety and Performance
The tread on overinflated tires does not contact the ground efficiently. When the bands bow outwardly, you lose a portion of the tire’s footprint. This shape reduces your ability to grip the road and control your vehicle.
Underinflated tires are even more dangerous. They drag part of the sidewalls across the pavement. Exposed edges heat up which leads to separation. Underinflated tires also tend to squirm more while cornering. High friction and stress increase your risk of tire failure.
4. Be Environmentally Friendly
Underinflated tires might cost you a little extra money in fuel, but they also have a more significant impact on the environment. Burning more fuel makes your vehicle pollute more, and your engine’s electronic control system adapts to this condition.
Your engine’s computer eventually gets used to struggling against a higher rolling resistance, and it learns to spend more fuel and vent more emissions to make up for the difference. It’s also harder on your other systems like your catalytic converters.
Worn out tires also need to be disposed of more often. In some places, a tire disposal fee is included on your repair bill whenever you purchase a new set. This charge takes care of only some of the cost to transport and store your used tires. Prolonging the life of your tires reduces the impact on landfills.
5. Decrease Road Noise
All vehicles produce some road noise, but the sound gets louder with underinflated tires. They drag more and scrub against the pavement. Inflating them to proper levels helps to reduce this sound slightly. You may not notice a big difference right away, but long-term neglect adds up.
Tire pattern noise comes from air escaping between the grooves as the tread strikes the ground. Engineers work relentlessly to design patterns that cancel as much noise as possible. An underinflated tire eventually develops a wear pattern that destroys the noise canceling properties designed into the treads. Keeping tires inflated preserves your quieter ride through the life of your tire.
Get the most mileage out of your vehicle tires and improve performance. Make tire pressure checks a part of your weekly maintenance routine.