How Do I Read My Tire Size On My Sidewall?
The tire size branded on the sidewall provides a significant amount of information about the tire's intended purpose, dimensions, load capacity and high temperature/high speed durability.
Our primary example will be based on variations of the 225/50R16 size, although other sizes will appear where appropriate.
"The tire size branded on the sidewall provides a significant amount of information about the tire's intended purpose, dimensions, load capacity and high temperature/high speed durability."
Service Type
Most tire sizes begin with a letter or letters that identify the type of vehicle and/or type of service for which they were designed. The common indicators are as follows:
P = When a tire size begins with a "P," it signifies the tire is a "P-metric" size that was designed to be fitted on vehicles that are primarily used as passenger vehicles. If there isn't a letter preceding the three-digit numeric portion of a tire size, it signifies the tire is a "Metric" size (also called "Euro-metric" because these sizes originated in Europe).
HL = When a tire size begins with an “HL,” it will also end with an “XL.” This signifies the tire has higher load carrying capacity than an “XL” tire of the equivalent dimensions.
T = If a tire size begins with a "T," it signifies the tire is a "Temporary Spare" that was designed to be used temporarily only until a flat tire can be repaired or replaced.
LT = If a tire size begins with "LT," it signifies the tire is a "Light Truck-metric" size that was designed to be used on vehicles that are capable of carrying heavy cargo or towing large trailers.
LT = If a tire ends with "LT," it signifies the tire is a "Flotation" Light Truck size designed to be used on vehicles that are capable of carrying heavy cargo and towing trailers.
C = If a Euro-metric sized tire ends with a "C," it signifies the tire is a "Commercial" tire intended to be used on vans or delivery trucks that are capable of carrying heavy loads.
ST = If a tire size begins with "ST," it signifies the tire is a "Special Trailer Service" size that was designed to only be used on trailers.
Section Width
Following the letter(s) that identify the service type, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.
Sidewall Aspect Ratio
Following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio. This is the “height” of the sidewall, expressed as a percentage of the section width.
Internal Construction
A letter (R in this case) that identifies the tire's internal construction follows the two digits used to identify the aspect ratio.
R identifies that the tire has a Radial construction.
D identifies that the tire has a bias-ply (Diagonal) construction.
RF identifies that the tire has a self-supporting Run Flat construction.
Tire and Wheel Diameter
P225/50R16 91S The 16 indicates the tire and wheel diameter designed to be matched together.
Service Description
P225/50R16 91S The 91S represents the tire's Service Description. A Service Description identifies the tire's Load Index (91) and Speed Rating (S).
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