How to Determine Dirt Bike Tire Size
Before you attempt to purchase a new tire for your dirt bike, you need to know some basic information regarding the size of the tire so that you can avoid serious injury or even death that can result from operating a dirt bike on improperly sized tires. Dirt bike tires display the essential information in a series of numbers on the sidewall. Once you know how to decipher which number stands for what, you can use the information to choose the correct size tire for your dirt bike.
Instructions
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Metric Format
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1
Look at the sidewall of the tire that's currently on your dirt bike to find the numbers that indicate width, height and rim diameter. They should read like one of the following examples:
120/80-ZR-19TL
120/80-19Z
120/80-19
120/80ZR19TL
120/90Zx19TL -
2
Determine the size of the dirt bike tire by looking at the numbers only. The first number in the series (in this example, 120) is the width of the tire measured in millimeters.
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3
Look at the second number (80). This number designates the aspect ratio of the tire, or the height of the tire in the relation to the width.
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4
Locate the third number in the series (19). This number is the rim diameter or wheel size.
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5
Order the tire by asking for it by the numbers such as 120/80-19. The tire dealer will know exactly what you want.
Alphabetical Format
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6
Locate the string of letters and numbers on the sidewall of the tire, such as MU90-16B.
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7
Look at the second letter in the string. This letter is a code for the width of the rim. The following codes detail the rim widths on which a specific tire will fit. For example, tires with "U" width code with fit a rim between 2.75 inches and 3.50 inches wide.
G 1.60 - 1.85
H 1.60 - 1.85
J 1.85 - 2.15
L 1.85 - 2.15
M 2.15 - 2.50
N 2.15 - 2.75
P 2.15 - 2.75
R 2.15 - 2.75
S 2.15 - 2.75
T 2.50 - 3.00
U 2.75 - 3.50
V 3.50 - 4.00 -
8
Look at the next number in the series: 90. This is the aspect ratio or the tire section height divided by the tire section width, multiplied by 100.
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9
Take note of the last number in the series: 16. This is the rim size, which is the outside diameter of the rim.
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10
Ask for or order an alphabetical format tire by the string of letters and numbers such as MU90-16B.
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1
Tips & Warnings
In the example given under Metric Format: 120/80-ZR-19TL , "Z" is the speed rating of the tire. "R" designates it as a radial tire, and "TL" means the tire is tubeless. Metric format is the most commonly used by manufacturers of modern dirt bike tires.
In the example given under "Alphabetical Format", the letter "M" stands for motorcycle and the letter "B" stands for the load range of the tire.
Check your owner's manual to determine the correct size tire for your bike if you bought a used bike. People sometimes install tires that are not made for the bike.
References
- Photo Credit racer113 image by Clarence Alford from Fotolia.com
