Today’s Express Car Care article discusses the effect of tire tread depth on braking.  When we talk about stopping power, drivers tend to focus on brakes.  But our tires are where the rubber meets the road.  So having good brakes isn’t always enough.  Every motorist has to have tires with enough traction to translate braking power into stopping power.

Let’s focus on stopping in wet weather 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 the thin film of water.  This is called hydroplaning.  We want our customers to know that if you hydroplane you won’t be able to stop as fast and if it’s really bad, you can actually spin out of control.

So how does a tire move water?  It has channels for water to flow through.  Look at a tire and you’ll see 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.  These channels are called treads and the deeper the tread, the more water it can move.  A brand new tire has very deep channels or tread and can easily move a lot of water.  As the tire wears down, the tread becomes shallower and can move less water.  When it wears down enough, it can seriously affect your ability to stop on wet roads.

That is why it’s so important for drivers to replace the tires on their vehicles when they get worn.  Consumer Reports and other advocate groups call for a standard of 3/32 of an inch and have studies to prove it.

You might have 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.  This little bit of added tread makes a big difference in your stopping power.

If you’re curious about your tire tread depth, 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.  We’ve recommended this before only using a penny, but the times have changed and a penny shows only half of the suggested amount for tire tread depth.

Give us a call of come in and see us if you have any more questions.

 

 

 

Question:

How can I tell when my tires are worn so much that they need to be replaced?

Express Car Care Answer:

That is an important question for car owners.  As we discuss the matter, keep in mind that one of the essential jobs of your tire tread is to move water.  The channels in the tread act as passages for water to escape from underneath the tire.  The deeper the tread depth, the deeper the channel – and the more water that can be evacuated.

When enough water can’t be moved from underneath the tire, the tire can ride on the water – often called hydroplaning.  The tire is literally not contacting the road but rather is “floating” on the water, so there is little traction and the truck or car can slide.

So somewhere between a brand new tire and a bald tire lies the point at which the tire should be replaced.  Some governmental jurisdictions have a minimum tire tread depth requirement for auto owners – others do not.  So check the important laws where you live to learn the legal minimum.

Tire manufacturers are required to mold a tread wear bar into the tire.  This bar appears across the tread when the tire is worn down to 1.6mm ( 2/32 of an inch).  Drivers can easily do the quarter test ( they used to use a penny, but I guess inflation has affected everything).  Insert a quarter into one of the grooves with the caribou’s head pointing down.  If you can see the tip of the nose of this great northern animal, it is a sign of very worn treads.  That means it is high time to bid adieu to your tires.

Studies have shown, however, that there is an essential difference in stopping distances for auto owners in detrimental wet conditions with tires that have less wear.  For example, in controlled, wet conditions a vehicle with 3.18mm ( 4/32 of an inch) of tread traveling at expressway speeds was able to stop in about 85 feet ( 26 meters) less distance than the same car with tires with 1.6 mm ( 2/32 of an inch) of tread.  That could easily be the difference between a safe stop and hitting the vehicle in front of you.

New tires are a big ticket item for motorists so it’s natural to want to get as much value out of them as possible.  Just remember that a huge part of the value is the ability to stop safely in wet conditions.  You can speak with your Express Car Care technician for answers about tire replacement.