Motorcycles subject tires to an enormous range of forces, stresses and heat. Fortunately, motorcycle tires are overdesigned to be able to meet those needs and still have reserve. So why do some tires fail? Most motorcycle tire failures come as a result of low tire pressures and excessive weight. No wonder tire manufacturers rate tire pressure as the number-one priority and they strongly urge riders to check it regularly. So, if we’re going to become fanatical about anything, it should be about religiously checking our tires and avoiding the sins of overloading them.
“Overload and underinflation is a bad, bad combination on any motorcycle,” Dunlop’s Mike Manning explains. “It creates excessive flex in the tire and an excessive heat buildup that can negatively affect handling and could ultimately result in tire failure–for any kind of tire.” Unfortunately, overlooking tire maintenance is all too common, even among active long-distance riders. “In our travels to rallies and other motorcycle events, we routinely find motorcycles with badly neglected tires. We have found tires with multiple nails—some clearly from different times—and a high percentage of tires that were significantly underinflated.” Perhaps that’s because it’s difficult to see when a motorcycle tire is low in air.
You can tell when most car tires are underinflated by as little as 5 pounds because the sidewalls visibly bulge. In contrast, a motorcycle tire must be nearly out of air before it appears to be low in air. The motorcycle tire is much more stiff by design, so giving the tire a kick or pressing the center with your thumb to see if it has enough air inside just won’t do the trick. That’s why it is so important to regularly check air pressures and keep them at their prescribed levels—even more so when carrying passengers or otherwise loading the bike. How often? Check pressures and visually check tires for foreign objects daily on a trip and weekly otherwise. And be sure to adhere to the motorcycle manufacturers’ GVWR limits to avoid overloading tires. Use the worksheet below to assure that you are not exceeding the limits of your motorcycle and contributing to potential handling and tire problems.
AVAILABLE LOAD CAPACITY:
1. Enter GVWR (Gross Vehicle Weight Rating). Check owner’s manual or Vehicle Identification Number (VIN) plate. 1. _______lbs.
2. Enter dry weight of motorcycle. Check owner’s manual. minus 2. _______lbs.
3. Average weight of fluids (gas and oil). minus 3. 40 lbs.
4. Available load capacity of your motorcycle (Line 1 – Line 2 – Line 3): 4. _______lbs.
LOADING OF YOUR MOTORCYCLE:
5. Enter total weight of rider and passenger. Include helmets, boots and clothing. 5. _______lbs.
6. Enter weight of accessories you have added, including chrome, windshield, saddlebags, etc. plus 6. _______lbs.
7. Enter weight of any cargo/luggage you are carrying. plus 7. _______lbs.
8. This is the load you are adding to your motorcycle (Line 5 + Line 6 + Line 7): 8. _______lbs.
If line 8 is greater than line 4, YOUR MOTORCYCLE IS OVERLOADED. Overloading your motorcycle could lead to tire failure, accident, injury or death.
Courtesy, Motorcycle Industry Council
The above is compounded further when tires are underinflated. Be sure to check tire pressures and make certain those pressures are appropriate for the load on the bike (most motorcycle manufacturers list different tire pressures for riding solo vs. when riding with the bike loaded and/or two-up).
(This article was published in the July 2012 issue of Rider magazine as a sidebar to Tales from the Dark Side: Putting Car Tires on Motorcycles)