article on tyre tread patterns

[Hanno Spoelstra]

As tyre tread patterns are often a subject for discussion, I quote an informative excerpt (including images) from an article on this subject that David Doyle did a year or so ago for Military Vehicles Magazine.

"While many types of tread patterns have been used on US military vehicles, including some quiet unusual patterns, most US military tactical vehicles during the WWII through Vietnam era used one of four tread patterns.

These were a directional chevron tread pattern, a non-directional cross country tactical tire, a non-directional mud and snow combat tire, and a non-directional Firestone tread tire. While the tread pattern of the directional tire makes it readily identifiable, the other three have similar tread patterns that make them easy to confuse.

As a rule the tire tread pattern is molded into the sidewall of the tire along with a wealth of other information, usually in abbreviated form. Non-directional cross-country is usually marked as NDCC, while the non-directional mud and snow tire is abbreviated NDMS or NDT.

The shoulders of the tread area of the NDCC tire are rounded, while the shoulders of the NDT tires have a more squared appearance.

Tires on most commonly collected US military vehicles are of bias-ply construction and are sized by rim width and diameter. These sizes are imprinted on the sidewall of the tire. As an example, a 9.00-20 (commonly referred to as a "nine hundred twenty) tire, fits a twenty inch diameter rim that is nine inches wide at the bead seat.

Also inscribed on the sidewall will be the tire size. Tires for classic military vehicles are usually sized using the numeric system shown here. Authors, including this one, often erroneously write these tire sizes in the format used for flotation tires, but as can be seen here, the tires described by the two systems are quiet different.

Other markings frequently found on the sidewalls of military tires are as follows:
- Manufacturer's name
- Ply rating-not necessarily the actual number of plies, but their equivalent.
- N-nylon cord"