The minimum tread depth of all major grooves on tires that are not on the front of a CMV should be a minimum of:

When inspecting your tires, verify that there is at least 4/32 of an inch of tread depth in every major groove on the front tires, and tread depth of at least 2/32 of an inch on the other tires. Tires on the same vehicle should all be the same size.