When a tire is under inflated, several things happen.  First of all, it is less rigid, which creates more rolling friction and increased heat.  Additionally, the sides of the tire bend and flex too much.  The flexing and bending generates even more heat.  This heat can exceed the ability of the tire to dissipate it, especially on hot days, and can cause serious damage to the tire, including tread separation and blowout.

Under inflation is dangerous for another reason, as well.  In the presence of water on the roadway, under inflation can result in hydroplaning.  Hydroplaning occurs when the water pressure under the tread exceeds the air pressure inside the tire, pushing the center of the tire off the road, and causing the tire to become concave.  When that happens, the tire essentially starts to ride on the small stream of water underneath it.   Steering at that point is lost, as the tire goes in the direction the stream of water takes it.

So how do our tires become under inflated?  Obviously, they could develop a slow leak from a puncture or a leaky valve stem.  But perfectly good tires lose air too, in fact as much as one pound per square inch (psi) per month.  Moreover, as temperatures drop, perfectly good tires can lose one additional psi for every 10-degree drop.

The solution to under inflation is simple—know the correct tire pressure for our tires, check them on a regular basis, and keep them properly inflated. Unfortunately, most of us do not check our tire pressure as often as we should.  When was the last time you checked the pressures on your bike?  If it was before our cooler weather, it’s almost a certainty your tires are low—mine were.

The key to proper inflation is developing a weekly routine—a little time well invested.  We need to keep in mind that front and rear tire pressures may not be the same.  On dressers, for example, when there is a rider and a passenger, the recommended pressure for the front tire is 36 psi, while the rear tire is 40 psi.

So, where do we find the proper inflation numbers?  If we’re running stock tires, the recommended tire pressures are in our Owner’s Manual.  For other than stock tires, information should be obtained from the tire manufacturer.  (Note: The pressure listed on the tire sidewall is a maximum that should never be exceeded, but it may not be the recommended pressure.)  And remember, tires should be checked when they’re cold, that is after they’ve set a couple hours, or only been used for a short trip to the service station.  Ride safe and have fun.