YOU hear it endlessly on every news cast, every automotive repair shop’s walls, every website, and every place that talks about how to save money: Make sure that your car’s tires are properly inflated. Under-inflated tires rob your vehicle’s fuel economy, increases emissions, and poses a significant safety risk, as under-inflated tires are liable to blow out.
Many of these same automotive groups will tell you to inflate your tires according to the vehicle’s instruction manual. Or they’ll say to inflate them to the instructions on the little placard inside your driver’s side door. Those typically say to inflate your tires to between 30-35 psi.
However, I believe this is insufficient. Modern steel-belted tires are not your grandfather’s synthetic-rubber radial single-ply tires. Modern tires are capable of taking far more pressure, passing much more stringent quality control standards, and consequently, can be inflated beyond the door placard. If you need any proof of this, consider the cover photo of this post. This image is courtesy of Bobby Ore Motorsports out of Florida. He is driving a Ford Ranger on two wheels. The tires are inflated to 100 psi, and are actually tires and wheels from a Ford Crown Victoria! It’s a dramatic expression of how much stress a modern tire can handle, and more importantly, how higher pressure keeps a tire in shape.
Now, I’m not saying you fill your tires to the point of exploding in the name of a few MPG. I recommend that you inflate your car’s tires to the maximum rated sidewall pressure, which is stamped on the side of the tire. For most passenger car tires, this is usually 44 psi. Regardless of what your vehicle is, use the maximum pressure stamped on the tire’s sidewall. This is completely within the tire’s design specifications and will have no adverse consequences except perhaps a bumpier ride.
Before I launch into the benefits of higher tire pressure, let me kill one myth: the center of the tread will not “balloon out” causing uneven wear above 30-35 psi. As I mentioned before, modern tires are built to much better specifications and quality control than the tires of yesteryear. There is a steel belt that prevents tires from being forced out of shape.
Increasing tire pressure helps to reduce the amount of unnecessary contact a tire has with the road, reducing rolling resistance. The constant flexing and bending of the tire, especially at highway speeds, heats them up considerably during the course of your daily drive – and this is wasting energy. Increasing the tire pressure reduces this. This helps your car coast further and also reduces the amount of power needed to maintain speed, especially on the highway. All of that translates to savings at the pump.
In addition to improved fuel economy, higher tire pressure also results in dramatically improved handling. When taking a hard corner, lateral gravity will literally force an under-inflated tire to deflect from the tread onto the sidewall – and you’re effectively driving on the side of your tire while taking a corner. The sidewall has almost no gripping power. Consequently, with a tire at less than maximum sidewall pressure, you risk losing control of the car completely (usually due to catastrophic understeer). As an additional benefit, reducing the amount of unnecessary tire contact with the road decreases your chance of hydroplaning in wet weather.
If you don’t believe me, then test it yourself – especially if you like to take turns and corners fast. Check the tread of your tires with a penny. I guarantee the outside of the tire’s tread has worn more quickly than the center of the tire.
I personally run 51 psi in my tires – which is the exact number on the sidewall of the tire. I average 55 MPG in a Prius, a vehicle that’s only supposed to get 46 MPG. And the tires have worn evenly over the past 30,000 miles. How about you?
(Image courtesy of Bobby Ore Motorsports, Sebring, FL.)