Welcome to the Loren's Auto Repair automotive blog. Today, let’s talk about the effect of tire tread depth on braking. When talking about stopping power, most Kalispell and Big Fork auto owners tend to focus on our brakes. But our tires are where the rubber meets the road. So having good brakes isn’t enough. Safe Big Fork drivers need to have tires with enough traction to translate braking power into stopping power.

Let’s focus on stopping in wet Big Fork 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.

That’s called hydroplaning. If it’s really bad, Big Fork auto owners can actually spin out of control - endangering themselves and the other drivers around them. At best, you won’t stop as fast.

So how does a tire move water? It has channels for water to flow through. Look at your Subaru 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 Loren's Auto Repair 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 your Subaru on wet Big Fork roads.

So that’s why it’s so important for MT auto owners to replace their Subaru tires 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 bald Subaru tire.

At Loren's Auto Repair, we want our customers to know that the deeper recommended tread depth makes a big difference. Stopping distances are cut dramatically on wet Big Fork interstate. A safe stop from MT interstate 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 Subaru tires. With a Canadian quarter, the tread should cover the numbers in the year stamp.

Many Big Fork auto owners have heard of this technique using a penny and Abe Lincoln’s head - the old method. That measure gives you 2/32 of an inch – half the suggested amount. Of course, Subaru tires are a major purchase. Most of us in Big Fork want to get as many miles out of them as we can. But there’s a real safety trade-off. It’s your choice.