Why it a affence to have low tread tires?

Answer 1

I assume you mean offense and by that I assume why is it illegal.

In the United States, 42 states dictate that a tread depth of 2/32's is the minimum allowable on a passenger car tire tread. That is 1/16ths of an inch to those who flunked fractions in elementary school. That is the approximate distance between the base of a new penny and Abraham Lincoln's head.

Consumer reports published an article in 2007 that their research indicated 4/32nds should be the minimum tread depth based upon braking and steering tests. That is the approximate distance between the base of a new quarter and George Washington's head. That is 1/8ths of an inch.

Tread is placed on tires to take water away from the tire and the road surface and increase the coefficient of friction (a measurement of traction) in inclement weather. Some tread patterns and tire materials are better than others in different situations which is why tire companies sell snow tires, rain tires, and all season tires. All tires are a combination of give and take on what is the best tread pattern, tire rubber compounds, construction, etc.

As the tire tread wears, this might increase traction in dry conditions which is why drag race cars often use "slicks" tires with no tread pattern, but these are useless if the roadway gets wet and no one can predict where and when that might happen on public roads. More tread reduces this potential for loss of traction significantly, but only if it is of sufficient depth and the research indicates that tires should be replaced when the tread depth is at least 2/32nds and preferably by 4/32nds.