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. The tire size will also indicate what size rim strip and motorcycle inner tube is needed. Rim strips are rubber strips that go around the rim, covering the inside edges of the spokes, before the tire is mounted. They help protect the inner tube from a potential puncture from continual wear against the spokes. Inner tubes are common, though tires are also run without tubes on many modern motorcycles with mag wheels.

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, H=130mph, V=149mph, W=168mph)
F- Tubeless (TL) 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 (Triumph, BSA, Norton etc.) 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 motorcycle 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



2 thoughts on “Motorcycle Tires: Understanding Tire Sizes and Codes”

  • might want to include mfg. date and tire age into

  • I liked how you said that inner tubes are common but there are also tires without tubes. I can see how this would be important to know when going to buy new tires for your motorcycle. Finding the right tire can be easy if you know a little bit about them beforehand.

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