Under what condition does a rear tire fail an inspection?

A rear tire fails an inspection when the tread on two adjacent grooves is less than 1.5 mm because this depth is crucial for maintaining adequate traction and grip on the road. Tread depth is a key factor in determining a tire's performance, especially in wet or slippery conditions. If the tread is too shallow, the tire may not be able to effectively channel water away, which increases the risk of hydroplaning and can significantly compromise vehicle safety.

While sidewall cracks, uneven wear, and asymmetrical tread patterns can indicate potential issues with the tire's integrity or performance, they do not have a specified measurement threshold like tread depth does. In Ontario trucking regulations, maintaining a minimum tread depth is particularly emphasized as it directly relates to safety and the operational capacity of the vehicle.