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Tire Size

How to tell Tire Size:

A typical tire size would be 235/75 15

Tires come with standardized tire code sizing information, found on the sidewalls of the tires. The first letter(s), indicate the vehicle type (P for passenger, LT for light truck). The next three digits indicate the tire’s width in millimeters. The middle two digit number indicates the tire’s height-to-width ratio. The next character is a letter “R”, which indicates radial ply tires (rather than radius). followed by a final two digit number indicating the rim size for the vehicle’s wheels.

Additionally, the correct Society of Automotive Engineers (SAE) class of snow chains must be installed, based on the wheel clearance of the vehicle.

SAE traction device classMinimum tread-face clearance (A)Minimum side-wall clearance (B)
Class S1.46 in (37 mm)0.59 in (15 mm)
Class U1.97 in (50 mm)0.91 in (23 mm)
Class W2.50 in (64 mm)1.50 in (38 mm)

The SAE Class “S” well clearance is a common requirement on newer cars, especially if after-market wider, low-profile, or larger tires and/or wheels are fitted.

The classes are defined as follows:[7]

  • SAE Class S: Regular (non-reinforced) passenger tire traction devices for vehicles with restricted wheel well clearance.
  • SAE Class U: Regular (non-reinforced) and lug-reinforced passenger tire traction devices for vehicles with regular (non-restricted) wheel well clearances.
  • SAE Class W: Passenger tire traction devices that use light truck components, as well as some light truck traction devices.
Class S tire clearance
A=1.46 in (37 mm) or more
B=0.59 in (15 mm) or more