Today’s KC Metro Select article discusses the effect of tire tread depth on braking. When talking about stopping power, Kansas City drivers tend to focus on brakes. But our tires are where the rubber meets the road. So having good brakes isn’t enough. Kansas City motorists have to have tires with enough traction to translate braking power into stopping power.
Let’s focus on stopping in wet Kansas City conditions. In order for a tire to have good contact with the road, it has to move the water out of the way. If it can’t move the water, the tire will actually ride on top of a thin film of water.
So how does a tire move water? It has channels for water to flow through. Look at a tire and you’ll see channels: channels that run around the tire and channels that flow across the tire. They’re designed to direct water away from the tire so it can contact the road better.
And the deeper the channel, the more water it can move. A brand new tire has very deep channels and can easily move a lot of water. As the tire wears down, the channels become shallower and can move less water. When it wears down enough, it can seriously affect your ability to stop on wet Kansas City roads.
So that’s why it’s so important for Kansas City drivers to replace the tires on their minivans when they get worn. Consumer Reports and other advocate groups call for a standard of 3/32 of an inch and they have the studies to prove it.
By comparison, you’ve probably seen the wear indicator that’s molded into tires. When tires are worn 3/32 of an inch, the tread wear bar is visible. So the recommended standard has twice the tread depth as a completely worn out tire.
And that little bit of additional tread makes a big difference. Stopping distances are cut dramatically on wet roads. A safe stop from MO freeway speeds with 4/32 of an inch of tread would result in a crash with worn out tires.
There’s an easy way to tell when a tire’s worn to 4/32 of an inch. Just insert a quarter into the tread. Put it in upside down. If the tread doesn’t cover George Washington’s hairline, it’s time to replace your tires. With a Canadian quarter, the tread should cover the numbers in the year stamp.
You’ve probably heard of this technique using a penny and Abe Lincoln’s head. That measure gives you 2/32 of an inch – half the suggested amount.
Of course, tires are a big ticket item for Kansas City car owners. Most of us want to get as many miles out of them as we can. But there’s a real safety trade-off. It’s your choice.