Part 2
"Tread Patterns
Chevron tread
Early in WWII many vehicles were equipped with chevron tread pattern tires, as can be seen in figure one. The chevron-type tread is a directional tread, which made tire rotation and replacement more time consuming.
According to TM 31-200, Maintenance and Care of Pneumatic Tires and Rubber Treads, April 1942, these type tires were to be mounted with a specific orientation.
When mounted on the rear driving axles, the tires should be mounted such that the point of V touches the ground first. This orientation allows the tread to clean itself of mud, giving superior traction.
When this type tire is mounted on the front axle of a vehicle, the open end of the V should meet the ground first whether or not the axle is driven. This is because the tire tread will wear more slowly when in this position. This stands to reason since there is also less traction when mounted in this manner.
The next edition, April 1943, made an exception to the previous policy. Directional tires when mounted on the front axle of scout cars and halftracks should be mounted just like the rear axles, that is with the point of the V touching the ground first.
When mounted on trailers, these tires were to be mounted for maximum tread life; that is with the open end of the V touching first.
Reportedly, when driven on hard surface roads, chevron tread tires on the steering axle tend to increase tire "hunt," making driving laborious.
Non-directional treads
During WWII the most common tread pattern found on tactical vehicles was the NDT, the non-directional tread. Characteristic of these tires was a very squared intersection of the tread area and the tire sidewall, as can be seen in figure two.
The tread known as the Firestone tread was very similar to the NDT, only the tread lugs of these tires had a slight twist to them, as shown in figure three. Although not as widely used as the NDT, they nevertheless were found on such vehicles as the GPW, CCKW, etc.
Non-directional cross-country treads were developed a little later. While at a glance they appear to be identical to the NDT tires, they are in fact different. Unlike the square shoulder of the NDT, the NDCC has a rounded cross-section. This rounded shape is clearly visible in figures two and four."
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