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Motorcycle Tires: Understanding Tire Sizes and Codes

To most people, the numbers and letters on the side of their tires are cryptic and indecipherable. This guide will help you understand the codes on the side of your motorcycle tires to be sure you know which tires you are currently using, and which others will fit your motorcycle. 

Typical Tire Markings
A- Tire width
B- Aspect Ratio. The smaller the number the lower profile of the tire. In metric this is a ratio between height and width. ex. A 170/80 means the width is 170mm, and the height would be 80% of that. )
C- Rim diameter
D- Load capacity
E- Tire speed rating (ex. S=112mph, V=149mph)
F- Tubeless (TL0 or Tube Type (TT) tire.


Tire Sizes
Size may be indicated in inches, metric, or by letters (alpha). It is helpful to know how these compare with each other so you can compare different brands of tires and see which might be the best fit for your bike. This chart shows the approximate comparison of the different size indicators.

Street Tire Conversion Chart

Inch2.75 / / 4.004.25 / 4.505.00 / 5.105.506.00




Rim Widths
British motorcycle rims are marked with a letter and number designation. This is helpful to know what tires you can mount on your rim based on the manufacturer's specs.

1.50 inches1.60 inches1.85 inches2.10 inches




Common Tire Sizes
The following chart shows some common tire sizes, including their width and the diameter. Very handy when choosing which tire will fit your bike, or which rear fender to buy to fit the tire you want to run on your new build!

BrandSizeWidth (inches)Diameter (inches)
Avon Safety Mileage MKII5.00-165.226.3
Avon Safety Mileage MKII4.00-184.426.7
Avon Safety Mileage MKII4.00-194.327.6
Dunlop D401130/90-165.125.4
Dunlop D404130/90-165.125.4
Dunlop K704.00-184.1726.73
Duro HF3025.10-165.325
Firestone Deluxe Champion4.00-184.2526.6
Firestone Deluxe Champion4.00-194.2527.6
 Firestone Deluxe Champion 4.50-184.8427.4
 Firestone Deluxe Champion5.00-165.3526.4



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