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Learn Tire Terms & Definitions

  1. OVERALL WIDTH This defines the overall width of a tire, width is measured from the inner to the outer sidewall. If your tire has a lip bead (or protective rib or raised lettring) then this is included in the measurement.

  2. SECTION WIDTH This is the measurement of the tires width from sidewall to sidewall (not including the protective ribs). It is important that this measurement be taken when the tires are properly mounted and inflated with no load on the tires.

  3. FREE RADIUS This is the distance from the wheel’s axle center to the outer tread surface of the unloaded and properly inflated tire.

  4. STATIC LOAD RADIUS This measurements is measured with load on the tire and is taken from the axle centerline to the treat contact area or patch.

  5. DEFLECTION The measured difference between the tire’s free radius and the loaded radius when mounted on a rim which is inflated to test pressure and under a prescribed or predeterminded load

  6. TREAD WIDTH The distance from the outer edge to the inner edge of the tread.

  7. TREAD RADIUS The design curvature or contour of the tread profile.

  8. SECTION HEIGHT This measurement off of he vertical distance between the tire’s bead seat and outer tread surface when properly mounted and inflated with no load on tire.

  9. NORMAL RIM DIAMETER This is measured as a linear distance between the bead seats which are taken at the widest point.

  10. OVERALL DIAMETER You probably don’t need help understanding this but it’s the distance from the tread surfaces at its widest point. The tire should be aired to the prescribed air pressure and under no load.


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