MOTORCYCLE TIRE BASICS
The simplest route to choosing new tires is to install tires identical to those you’re replacing. This is fairly easy if you’re riding a motorcycle manufactured within the past 10 to 15 years.
Many motorcycle tire companies today still produce tires that are either identical to those you’re replacing, or are suitable replacements designed to work with your specific model of motorcycle. At the very least, if an identical replacement isn’t available, tire manufacturers will offer a number of tires that will work in the broader category of your type of motorcycle, i.e. the 600cc sportbike class or the heavyweight touring motorcycle segment.
However, best practice is to select replacement tires identical to those currently on the motorcycle.
A fact too infrequently mentioned is that motorcycle manufacturers will go to great lengths to develop a motorcycle’s handling performance around a tire of particular construction.
Motorcycle companies will work directly with one, perhaps two, tire manufacturers to produce a tire set that will allow the motorcycle to perform exactly how the bike maker intended. Selecting a tire with different dimensions, even marginally different than the tire fitted as original equipment, can dramatically alter the way a motorcycle steers, stops or accelerates.
Often these changes in the bike’s performance are for the worse, although there are instances where handling improves when a tire slightly different than the original is used. Knowing your motorcycle intimately will help you determine if the motorcycle manufacturer intended a specific tire for your machine.
An original equipment tire is usually costly to replace, especially when purchased from a motorcycle dealer that sells the same brand of motorcycle for which you’re looking to fit new tires. So, are you left with no option but to pay the piper? Not necessarily.
Like many things in life, with bike tires there are often exceptions to the rule; despite motorcycle makers designing around a specific brand and model of tire, as a rider you have options in tire choice, a choice which is often influenced by the coins in your purse.
The primary piece of data needed to begin your tire search is the exact model and year of your motorcycle. With this seemingly trivial bit of information a dealer, large motorcycle parts and accessories retailer, or your local independent shop can immediately offer you a number of tire choices from a variety of tire makers. At that point you might choose to select the least expensive tire, and call your job done.
On the other hand you might want to choose between longer wearing tires for increased mileage, or those that provide mileage similar, or slightly less, to your original tire, but offer increased grip performance. Tire makers also design tires claimed to provide a smoother ride, quicker warm up time, or any number of other features that enhance tire quality.
The next step in better knowing the tires that will work on your ride is understanding tire size dimensions. Modern street tires have size data embossed on the tire’s sidewall. Metric sizes generally consist of three numbers arranged in this manner: XXX/XX x XX.
The first number is the tire’s width expressed in millimeters, though the mm designation isn’t printed next to the number. The second number following the slash mark is what’s known as the tire’s aspect ratio. This is the height of the tire’s sidewall expressed as a percentage of the tire’s width – put simply, it’s a ratio of height to width. The final number refers to the wheel diameter (also the inner circle of the tire) expressed in inches.
For the sake of easily understanding how to read a tire’s metric size dimensions we’ll use a common rear tire size found on modern sportbikes: 180/55 x 17.
The number 180 tells us the tire is 180mm at its widest point, while the second number, 55, says that the tire’s sidewall height is 55-percent (roughly 99mm) of the width of the tire. Finally, 17 tells us that this tire is for a wheel measuring 17 inches in diameter. The front tire will use the same sizing convention, but unlike most automobile tires with have matching sizes front and rear, the front tire on a motorcycle is almost always narrower than the rear, even if the particular bike uses identical diameter wheels for front and back.
Of course, a simple look at a motorcycle’s tires will reveal the disparity in widths of the front and rear tires. But in our ever-litigious society tire makers want to ensure consumers, and even professional motorcycle mechanics, know which tire is for the front and rear, so it’s not uncommon to see Front or F embossed on a front tire, and Rear or R embossed on a rear tire.
You’ll often also see a rotational direction indicator to prevent you or the shop from mounting the tire backwards, for lack of a better term, since most tread patterns are designed to work in one direction in order to effectively disperse water from the tire.
