How does tire tread depth affect braking on wet roads?

• A. Deep tread increases braking distance on wet roads.
• B. Tread depth has no effect on wet braking.
• C. Shallow tread reduces water displacement and increases stopping distance and risk of hydroplaning.
• D. Higher tread depth increases hydroplaning risk.

Answer: (C)

When braking on wet roads, the tire must pump water out from under the contact patch to maintain grip. Shallow tread can’t move water as effectively, so a layer of water stays between tire and road. That reduces friction, increases stopping distance, and raises the risk of hydroplaning, where the tire rides on a water film and loses traction. Deeper tread channels water away more efficiently, helping the tire stay in contact with the road, which improves braking performance and lowers hydroplaning risk. So the correct idea is that shallow tread impairs water displacement and increases both stopping distance and hydroplaning risk. The notions that deep tread worsens braking or that tread depth doesn’t matter aren’t accurate because tread depth directly affects how well water is expelled from under the tire.