Tires are one of the most critical safety items on your vehicle. They endure thousands upon thousands of high-speed revolutions as you cruise from place to place and ensure you have optimal grip when cornering and stopping. Without good tires, even a little water on the roads can cause you to slip.
This is why tire tread depth and other tire maintenance are so critical. Tire tread depth, which is the deepness of the grooves in the tread pattern, impacts its ability to grip in snow and channel water away from the tread to enhance grip. The shallower the tread grooves are, the less efficient it is at gripping in snowy and wet conditions.
Below, we outline how to measure tire tread depth and other valuable tire tips to ensure your tires remain in top shape as long as possible.
Before you can correctly learn how to measure tire tread, you must first know the main sections of the tread. Your tire's tread has three main sections: the outer shoulder, contact patch, and inner shoulder. Deep grooves — called channels or tread grooves — span the tire's circumference and separate the tread.
The outer shoulder is the tire's outermost section and is outside the last channel. On the opposite edge of the outer shoulder is the inner shoulder.
The contact patch is the area between the two shoulders and is the tire's main contact point with the road. This is where the tread blocks are thickest and where you measure the tire tread depth.
Determining a tire’s tread depth involves measuring from the deepest point in the channel to the top of the tread on the contact patch.
This depth is important because the channels guide water and slush away from the contact patch to maximize traction. If the tire tread depth is too low, the channels will be too shallow to move water and slush effectively, reducing traction and increasing the risk of hydroplaning on wet roads.
There are three relatively simple ways to measure tread depth, but some are more precise than others.
Looking closely at the tire's channels, you'll notice small, raised rubber bars going across them in some areas. These are tread wear indicator bars. If the tire tread wears to the point that it's even with the wear bars, your tires need replacing.
The nickel or quarter test is a simple way to check tread depth. Hold a quarter or nickel between your thumb and forefinger and place the coin inside the channel, with the top of the figurehead’s head facing the tire. If any portion of the tread covers the figurehead, your tire tread depth is OK. If the full figurehead is exposed, it's time for new tires.
Always check your tires in several places as they don't always wear evenly and could be low in some areas.
A tire tread depth gauge is the most official and accurate way to check tire tread. The tread depth gauge will have a blade side similar to a flat-head screwdriver and a gauge side with either a manual gauge with measurement marks or a digital readout. You can pick one up at any auto parts store for about $5 (manual) or $15 (digital).
Fully extend the blade side and place the blade into a tire groove between two tread blocks on the contact patch. Slide the gauge toward the tread until the gauge's flanges rest on the tread blocks on the contact patch. Read the measurement on the gauge.
Repeat the measurement on several parts of the contact patch to ensure there are no low spots.
Using a gauge will give you the most accurate results and allows you to compare your tire's tread depth to the requirements in your province. If you’re getting close to the minimum tire tread depth for your province, it’s time to consider replacing tires.
Canadian law requires a minimum 1.6 mm tread depth, but some provinces have even stricter requirements. The province-specific tread depth rules are as follows:
While the legal minimums are great, tire experts often note they aren't always the safest recommendations.
Large portions of Canada set the legal minimum tread depth at 1.6 mm. Tire Rack experts tested this minimum against 3.175 mm of tread. They found a vehicle with tires with 1.6 mm of tread required an extra 30.5 metres to stop from 112 km/h than the vehicle equipped with tires with 3.175 mm of tread.
For this reason, Tire Rack and many other automotive experts recommend new tires when your existing tires reach 3.175 mm of tread. Additionally, they recommend swapping out those snow tires at 3.96 mm.
To put this all in perspective, the average new tires have 7.94 to 8.73 mm of tread.
Many variables come into play when shopping for a tire, but much of the research is complete if you know what to look for.
Some shoppers follow the lead of the tire salesperson or service center mechanic who generally wants to sell the most expensive set of tires they can. Without fully understanding how tires work, assuming the priciest tire will last the longest and is best for safe driving is easy. But this is only sometimes the case.
A lot more goes into tire pricing than longevity. Special compounds also make the tire quieter, puncture resistant, or more stable in corners and braking, but this doesn’t always translate to longevity.
If your main interest is a long-lasting tire, avoid falling for a tire salesperson directing you to the higher-priced tires. Instead, focus on the Uniform Tire Quality Grade (UTQG) stamped on the sidewall. The UTQG will be a three-digit code followed by two letters.
The three digits are the treadwear rating, and the two letters are the traction and temperature rating. The higher the three-digit number, the longer the manufacturer expects the tire tread to last.
There are no exact numbers the three-digit code translates to, but understanding its meaning is simple. When determining a treadwear rating, the base control tire has a 100 rating. The tire manufacturer estimates a 200 treadwear tire will last twice as long as that control tire, a 400 will last four times as long, and so on.
So, a premium $150 tire may have only a 300 treadwear rating but many other attractive features that increase the price. However, there could also be a $70 tire next to it with fewer features but a 700 treadwear rating. If your focus is longevity, it's clear which is the right tire for you — although that $150 tire likely has benefits the $70 doesn’t.
Manufacturers estimate the treadwear rating by driving 11,520 km on a 640-km track. They stop every 1,280 km to check the remaining tread. They then use these measurements to determine the projected treadwear ratings.
Barring manufacturer defects, such as tread separation or sidewall bulges, tires will last as long as they should, given your vehicle is in good mechanical condition and properly maintained. However, you can take steps to maximize the life of your tires.
Tire pressure is the first rule for maximizing tire life. Check the air pressure in your tires weekly — or every time you refuel — and compare it to the pressure requirements on the tire placard in your door frame.
The recommended pressure will generally fall somewhere between 32 and 38 PSI. Too much air pressure can cause the centre of the tire to bulge, leading to excessive wear in the middle of the tire. Too little air can cause the centre to collapse, putting most of the car's weight on the outer edges, leading to excessive inner and outer wear.
As an added benefit, the correct tire pressure also helps with fuel economy.
Never fill your tires to the maximum PSI listed on the tire unless this is the pressure listed on the tire placard.
Today, many vehicles have a tire pressure monitoring system that displays all four tires’ pressures or simply alerts you if one tire is low. These can be great indicators but aren’t always accurate, so you should still periodically check your pressures manually.
Always check the tire pressure when the tire is cool, not after a long drive. As tires warm up, the pressure increases, leading to a false measurement.
Slippery driving conditions, like rain- or snow-slicked streets, can lead to wheel slip, creating excess heat and quickly wearing out tires. Always adjust your driving style to road conditions. You’ll avoid spinning the tires and prolong their life.
Tires rarely sit perpendicular to the road. Most manufacturers engineer the suspension system so the tires sit at a slight inward angle. This angle allows the tire and suspension to flex outward as you go around corners, so more of the tire's contact patch touches the road.
This means as you're driving straight, most of the car's weight rides on the inner portion of the tire. Rotating the tires in the manufacturer's specified intervals puts the tire in a different position on the vehicle, slightly changing its angle to prevent uneven tire wear.
Over time, all the flexing in the suspension and bumps in the road can throw off the angles. When a mechanic performs an alignment, they reset the angles so the tires are in the position the manufacturer recommends, ensuring they wear evenly.
Tires are far and away one of the most critical parts of automotive safety, so it’s important to maintain them properly. This maintenance goes beyond just rotating them and keeping the pressure within specifications. You must also monitor your tread depth to ensure there is enough to provide you with the traction you need.
Fortunately, there are several ways to measure tire tread, and some require no tools. All you need is good vision and maybe a coin. However, if you want to be 100% certain you’re legal and safe, shelling out $5-$15 for a tread depth gauge will help.
All our preowned vehicles at Clutch have been through a 210-point inspection, including the tires. Any tires with less than 4mm of tread depth are replaced with quality new tires, giving you peace of mind.
Plus, all vehicles purchased online come with a 10-day money-back guarantee that allows you to return the vehicle for a full refund within 10 days of receiving it. Beyond that, all Clutch vehicles have a 90-day or 6,000-km limited warranty.
Finally, our car-buying experience is 100% online and free from any high-pressure sales tactics of most used car dealerships. Check out our range of available vehicles and shop from the convenience of your home.