Tire Tech

Tire Specs Explained: Tread Width Measuring

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Tread Width Measuring

Tread width is typically thought of as a measurement between the outboard and inboard edges of a new tire's tread design. Ideally it approximates the width of the tread that comes into contact with the road. Unfortunately measuring tire tread width isn't as simple as laying a ruler across the tread.

While it's relatively easy to measure the square-shouldered designs used on many winter and off-road light truck tires, it is far more challenging to measure treads with multiple radiuses and rounded shoulders featured on most passenger and performance tires.

Square-Shoulder Tread

Measuring the tread width of square-shouldered tires is relatively easy, since the tread's edges are easily identifiable.

Round-Shoulder Tread

Measuring the tread width of rounded-shouldered tires is more challenging because identifying the tread edges is difficult.

Unfortunately there isn't an industry standard that establishes a single procedure for how to measure tire tread widths. And since tire manufacturers can use different methods, their published tread widths would only be meaningful when compared to other tires measured the exact same way.

This makes it challenging to compare tread widths of one tire brand to another, and most tire manufacturers have simply chosen to eliminate tread width dimensions from their brochures and websites.

Because tread width is still a dimension of interest to our customers, Tire Rack has established a common measurement method to address this issue.

The Tire Rack tread width measurement tool helps us define how much of a rounded shoulder's over-the-horizon tread width should be included in the measurement. We use a 20" long tool made with square tube featuring a 30° bend in the middle. Centering this tool on top of the tread design helps us approximate how much of the tread will be in contact with the road when in service.

TR Tool with Round-Shoulder Tread

Measuring the tread width of rounded-shouldered tires is defined by centering our tool on top of the tread and measuring the distance from the outboard to inboard contact.

Once we know the points of contact, we then use a flexible flat steel ruler to measure between those two points. This tool can be used on tires with rounded shoulders, as well as those with square shoulders.

While Tire Rack tread width dimensions may differ slightly from those published by the few remaining tire manufacturers that still offer them, it will be applied universally.


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