How does a motorist know when to have their tires changed? Any owner or driver of a car or truck should carefully inspect the tires on their vehicle once a month. This should also include a visual inspection of their spare and/or replacement tires. Although few drivers actually do this, it’s easy to spot when tires become worn and need to be replaced. Law Enforcement and CVSA international know tires can lose their footing long before they’re worn out. Our tests show that tread can give up a significant amount of grip when it’s still at the halfway point.
That’s particularly worrisome when you realize how many worn tires are on the roads.
All new tires sold in Canada come equipped with tread wear bars which are small raised bars that run across the grooves of the tire tread. They resemble small bridges that connect the ridges on the tread. When a tire is new and the grooves are still deep, the bridges are very difficult to see. As the tires wear out, they become more visible and as the tread and the tread wear bars become level, your tires are considered legally bald and need to be replaced. Worn tires—especially bald ones—can be deadly on wet roads, where the grooves aren’t deep enough to channel water out from beneath the tread. The result is hydroplaning, where the tread skims the water’s surface and the vehicle no longer responds to the steering wheel. Wet-weather braking and snow traction also decrease as tires wear. Actual road wear would have also aged the rubber, reducing grip even further. But differences between our half-tread and full-tread tires were striking:
Longer wet-weather stops. Reduced wet-weather braking can be even more dangerous than hydroplaning. Compared with new tires, those with half their tread depth took 3 to 6 feet longer to come to a stop from 40 mph on our wet track with the antilock braking system engaged.
Better dry-road performance. Bone-dry pavement is one place where less tread means more grip, since shallower grooves and sipes put more rubber on the road. That’s why mega-horsepower racing cars typically run on treadless “slicks” for all-out traction. It also explains why the half-tread tires performed better in our dry-pavement handling, cornering, and braking tests.
Tires wear out over time. Differences in speed, road conditions, inflation, vehicle maintenance, your driving habits, and temperature make it hard to predict exactly how long your tires will last. We recommend inspecting your tires regularly and replace them when they are worn down.
Here are three ways to measure your tread:
- Tread Depth Gauge
You can check this yourself with an inexpensive tread depth gauge, available at most auto supply stores. You’ll know to replace your all-season and all-weather tires when there is just 1.6-mm (2/32-inch) tread depth remaining. Winter Tires need a deeper tread to keep traction in the snow. We recommend replacing them when there is just 3.2 mm (4/32 inch) remaining.
- The Tire Wear Bars
Tires are manufactured with wear bars that indicate when there is less than 1.6 mm (2/32 inch) of tread depth remaining. When the tread is worn down to the point where you can see a solid bar of rubber across the width of the tread, it’s time to replace your tires.
Tread Region: The “flat” area of the tire that you drive on. The construction of the tread will determine the grip of the tire in different weather conditions. It will affect your speed, acceleration, braking, and cornering.
Shoulder and Sidewall Region: The vertical side of the tire that extends from the road surface to the rim. The construction of the sidewall affects the ride and handling of the tire. A stiff sidewall provides quick steering response, while a softer sidewall flexes to provide a smoother ride.
What those numbers on your tires mean:
There are three key pieces of information in the numbers moulded in the sidewall of your tire. We’ve broken down an example tire number of P215/65R15 89H below so that you can more easily understand the numbers on your tire and find the right replacement for your vehicle.
“P” indicates that this tire is made specifically for a passenger car, minivan, CUV, or SUV.
“215” indicates the tire width in millimetres from sidewall to sidewall.
“65” indicates this tire’s percent ratio of height to width.
“R” stands for Radial – the type of tire construction of nearly every tire on the market.
“15” indicates your rim diameter in inches.
Your vehicle is built and tested based on the manufacturer’s recommendation for tire size. Choosing a different tire size may affect your vehicle’s overall performance and durability.
“89” indicates the maximum weight this tire can carry: 1,279 lbs. This is not a number you need to be concerned with when purchasing tires, unless you’re pulling or carrying heavy loads.
“H” indicates the maximum speed at which this tire can drive: 130 mph. Your vehicle’s tires should be the same or greater than the manufacturer’s recommendations.
Recognize the signs of tire-wear problems:
If you notice any of these signs on your tires, it means your tires may not be wearing properly:
- Sawtooth appearance on the edges
- Faster wear on the outer edges than in the middle
- Quicker wear of front or rear tires on front-wheel drive vehicles
- Tire wears excessively on one side
- Cups or dips in the tread
There are a number of causes for tire-wear problems, including:
- Your tires are not properly inflated or balanced
- Your vehicle is misaligned
- The shocks on your vehicle are weak
- Your vehicle has loose front-end parts
Our professionally trained Fountain Tire associates can diagnose and address any tire issues you may have.
Do not mix tire types and sizes:
Tires with different size designations, constructions, and amounts of wear may affect vehicle handling and stability. For best all-around performance, we do not recommend mixing sizes and types of tires on a vehicle. It would negatively affect the handling characteristics of the vehicle. With winter tires in particular, Transport Canada recommends that tires get changed in sets of four only. It’s safer. That’s why we’ve made it our policy.
Did you know that each tire on your vehicle has to support a different weight? This unequal weight distribution causes your tires to wear down at different rates. By rotating your tires, you can extend the life of your tires. Check your vehicle owner’s manual for rotation recommendations. If no rotation period is specified, a good rule of thumb is to rotate your tires every 10,000 kilometres.
Additionally, the rubber compounds found in tires deteriorate over time and may be a cause for replacement. As your tires age, the rubber may begin to dry out, especially if the tires are exposed to a lot of sun. In some cases, cracking may appear on the sidewalls and in others it may only appear on the tread. Regardless, any evidence of cracking or drying is an indication that the tires need to be replaced.
To determine the age of your tires, refer to the Tire Identification Number beginning with the letters DOT, located on the inner and/or outer tire sidewall. For tires that were manufactured after the year 2000, the last four numbers of the code will identify the week and year in which the tires were manufactured. For example, the following identification number indicates that the tires were manufactured in the 51st week of the year 2008: DOT CX8J 3C2 5108. For tires that were manufactured before the year 2000, the date will be represented in the last three digits of the tire. For example, the following identification number indicates that the tires were manufactured in the 40th week during the 8th year of the decade: DOT U2LL LQLR 408.
Another factor to consider is that any damage to the sidewall of a tire, however small, will require a replacement. For example, if the vehicle shows signs of internal damage in the form of a slight bubble or wave on the sidewall, or there is damage from a protruding object, proper precautions need to be taken to ensure blow-outs are prevented. Have an expert inspect your vehicle if you suspect any faults in your tires.
Where and when you check your tires matters:
In one month, a tire can lose quite a bit of air pressure. Check your tire pressure at least twice a month. Air pressure increases with heat, so be sure to measure it before driving, while the tires are still cold. When the weather gets cold, check your tires outside to get the most accurate reading. If you store your vehicle in a heated garage and check the pressure inside, your air pressure reading could be up to 25% higher than the actual pressure. Refer to your owner’s manual to determine how much pressure (or PSI) your tires need, and use a tire gauge to get an accurate reading.
Running tire grooves down to 2/32 of an inch may be fine in arid regions where rain and snow are rare. But for rain or snow, you may want to consider replacing worn tires sooner, especially if you begin to experience reduced grip.
- Check tires for other flaws. Replace any tire with cracks, cuts, or bulges in the sidewall. Look for uneven wear, which usually signals a wheel-alignment or suspension problem. Either must be repaired to prevent premature wear.
- Stick with the sipes that your tires come with. Adding more, called siping, can hurt dry performance and longevity. Remember that even new tires don’t grip as well in rain or snow as on dry surfaces. To drive more safely in the wet:
- Slow down. And leave added room between your vehicle and the one in front of you. Safety experts recommend a two-to-three-second lag between the time the vehicle ahead passes a sign or other fixed object and the point at which your vehicle reaches it. Double that distance in rain or snow to give yourself more time to brake.
- If your tires hydroplane, back off the gas pedal to regain control.