Is the Legal Minimum Tire Tread Depth Enough?
No doubt this morning was an intensely exciting one for a driver that I passed by. She had obviously done some panicked steering on the rain soaked highway judging from the marks in the median and the amount of grass and mud in the fast lane. Others had already stopped to help and aside from being stuck in the median she and her vehicle appeared relatively unharmed.
This turned my thoughts to the tread on my tires and the question of how much tread is needed to stop and steer properly on wet roads. We know that tires are considered to be worn out at 1.5 mm or 2/32nds of an inch unless they are winter tires, in which case the limit is 3 mm or 4/32nds of an inch of tread depth. Is that really enough?
It appears that if you intend to drive on wet roads 4 mm may be the minimum tread depth needed to stop and steer effectively. Without at least this much tread the tire cannot move water away from the tread fast enough to maintain adequate traction. To drive with less tread is not illegal until you reach the legislated minimums, but it may not be safe.
One last thought and that is to buy a decent tire guage to keep in your glovebox. Use it every couple of weeks before you start out and make sure that the tires are inflated to the specifications on your vehicle's tire placard. Proper inflation helps tread do its part to prevent hydroplaning.