![tread]()
Your average motorcycle tire has more arcana etched on it than a copy of The Golden Bough. If you’re confused by all this code, here’s a handy guide to what it all really means.
TUBE DESIGNATION Tires are used with an innertube (Tube Type or TT) or without (Tubeless or TL). The tread and sidewalls may be made of differing numbers of layers, and include various materials (sometimes steel or fiberglass; usually nylon, kevlar, aramid, or other resilient fabrics).
LOAD/SPEED INDEX The number indicates how much weight the tire can bear. The letter denotes the maximum speed rating for the weight borne by that tire, when that tire is inflated to maximum pressure.
![Speed Index, Load Index]()
WHEEL ROTATION To perform safely, a tire has to rotate in the right direction and grip properly. If mounted backward, the tire’s tread might peel or tear.
PRESSURE RATING Tires often have a maximum tire pressure rating (which differs based on whether the tire is hot or cold). Your bike’s manual often has your suggested safe pressure rating, too.
OTHER INFORMATION Your tires might also bear some other markings: manufacture date, tread wear indicators, or mounting dots (for balancing or placement near the inflation valve on the wheel).
TIRE CODES
This complex set of numbers and letters (called the metric tire size system) carries a wealth of useful information.
Tire Width: This is measured in
millimeters; aspect ratio is the tire’s height as a percentage of its width. Low-profile tires can lower seat height and deliver a firmer ride, and are most often found on sportbikes; high-profile tires yield more tire flex and a softer ride, especially on dirt bikes and touring machines.
![Aspect Ratio]()
Speed Rating: Uses letters derived from the speed index to indicate the tire’s safe speed (which could differ from its maximum speed). If there is no speed rating, an M is placed before the width/aspect number, to show it is simply a motorcycle tire.
Tire Construction: Either “B” for belted (parallel to direction of travel) or “R” for radial (at a 90 degree angle, which most bikes use), or unlettered (for bias-ply tires, often found on dirt bikes).
Rim Diameter: Measured in inches (to fit the proper wheel size).
Other tire coding systems include: Alphanumeric (used on touring bike tires; letters and numbers denote width, aspect ratio and other info); Standard Inch (on older bikes and gradually being phased out; aspect ratio is always 100 percent); and Low-Profile Inch or 82-Percent Series (all of these tires have an 82-percent aspect ratio).
Your average motorcycle tire has more arcana etched on it than a copy of The Golden Bough. If you’re confused by all this code, here’s a handy guide to what it all really means.
TUBE DESIGNATION Tires are used with an innertube (Tube Type or TT) or without (Tubeless or TL). The tread and sidewalls may be made of differing numbers of layers, and include various materials (sometimes steel or fiberglass; usually nylon, kevlar, aramid, or other resilient fabrics).
LOAD/SPEED INDEX The number indicates how much weight the tire can bear. The letter denotes the maximum speed rating for the weight borne by that tire, when that tire is inflated to maximum pressure.
WHEEL ROTATION To perform safely, a tire has to rotate in the right direction and grip properly. If mounted backward, the tire’s tread might peel or tear.
PRESSURE RATING Tires often have a maximum tire pressure rating (which differs based on whether the tire is hot or cold). Your bike’s manual often has your suggested safe pressure rating, too.
OTHER INFORMATION Your tires might also bear some other markings: manufacture date, tread wear indicators, or mounting dots (for balancing or placement near the inflation valve on the wheel).
TIRE CODES
This complex set of numbers and letters (called the metric tire size system) carries a wealth of useful information.
Tire Width: This is measured in
millimeters; aspect ratio is the tire’s height as a percentage of its width. Low-profile tires can lower seat height and deliver a firmer ride, and are most often found on sportbikes; high-profile tires yield more tire flex and a softer ride, especially on dirt bikes and touring machines.
Speed Rating: Uses letters derived from the speed index to indicate the tire’s safe speed (which could differ from its maximum speed). If there is no speed rating, an M is placed before the width/aspect number, to show it is simply a motorcycle tire.
Tire Construction: Either “B” for belted (parallel to direction of travel) or “R” for radial (at a 90 degree angle, which most bikes use), or unlettered (for bias-ply tires, often found on dirt bikes).
Rim Diameter: Measured in inches (to fit the proper wheel size).
Other tire coding systems include: Alphanumeric (used on touring bike tires; letters and numbers denote width, aspect ratio and other info); Standard Inch (on older bikes and gradually being phased out; aspect ratio is always 100 percent); and Low-Profile Inch or 82-Percent Series (all of these tires have an 82-percent aspect ratio).