Check Those Tire Pressures

I was reminded recently how important it is to make sure you have the right amount of tire pressure. After my 1,000 maintenance (2009 Police Electra Glide…nice), both tires were just under 25 psi. Not optimum by far. The front tire should have been at about 36 psi and rear tire at about 38 – 40 psi.

Riding in the cold and then parking in a toasty warm garage overnight will wreak havoc on tire pressures coming from cold to warmer climates and vice versa over time. The general rule of thumb is for every 10 degrees F change in air temperature, your tire pressure will change by about 1 psi.

Since I have been riding in sub 30 degree temperatures, the change was significant enough for my tires to loose over 10 psi in about one month (actually 37 days). Shame on me, I should have been checking them regularly but became complacent about it.

We have a saying in police work, “complacency kills.”

Riding everyday may lull you into a similar complacency. It is extremely important your tires maintain the optimum psi. Low pressures will affect handling and stability.

Some Technical Stuff about Tires

Performance

What supports your motorcycle’s load? The tire does not support the load, the air pressure does. Compressed gas (air) inside the tire creates tension and allows the tire to function as a load-carrying device.

The manufacturer’s ratings for maximum load and inflation pressure are extremely important design elements. If not followed, the handling and performance of your motorcycle will be greatly affected.

Remember:

1. A tire must transmit handling (acceleration, braking, cornering) to the road surface
2. A tire also acts as a spring between the rim and the road. This is important to the vehicle’s ride.

Under/Over Inflation

Under inflated tires can result in imprecise cornering, reduce ability to support the load (traction), higher running temperatures, irregular tread wear at the edge of the contact patch, fatigue cracking, over-stressing and splitting in the sidewall.

Over inflating tires doesnot increase load carrying capacity, but will result in a hard ride through the transmitting of shock loads to the suspension, reduces the tire’s ability to withstand road impacts and cause tire wear.

Temperatures

Air pressure is affected by temperature.  Typically, an inflation pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. Higher temperature means increased pressure.

If a tire is inflated to 35 psi on a warm day in July, it could have an inflation pressure of 23 psi on a cold day in January. At 23 psi, you are severely under-inflated.

In contrast, if a tire is inflated to 40 psi on a cool summer morning and by the afternoon your in the 90’s, tire pressures can reach around 44 psi, possibly exceeding the maximum rating.

Checking Pressure

Check cold tire pressure frequently with a good quality gauge that holds a reading, and always before extended trips.

Check your pressures daily when you are on a trip and remember that every 1 psi of air lost is approximately equivalent to losing 60 or 70 pounds of load carrying capacity.

If you check pressure after riding for a while, keep in mind that more than a 10% increase in pressure indicates your tires are working too hard. Either lighten the load (probably not practical) or slow down. BTW, 10% is about a 4 psi difference.