What is the minimum tread depth for the steer-tire?

Answer: D — 4/32 inch

Steering tires need enough tread to maintain control, especially during braking and while steering through corners or wet roads. That’s why the minimum tread depth on front steering tires is set higher than for other tires: 4/32 inch. Among the options, 4/32 inch is the smallest depth that meets this requirement, so it’s the correct minimum. The other depths are either shallower than the steer-tire standard or deeper than necessary. To check, measure the tread in several grooves around the tire and ensure no groove is shallower than 4/32 inch on the front tires.