Tires are one of the most commonly replaced items on your vehicle as they endure thousands of miles of high-speed revolutions on hard pavement. As they shed their tread due to everyday use, they become less effective bit by bit.
Knowing how to measure tire tread will help you determine when it’s the right time to replace your tires. Without this basic understanding, you risk changing them too late and putting your safety at risk or changing them too early and wasting money.
Below, we'll cover how to measure tire tread and other tire-read-related topics to help you stay safe, save money, and know what to look out for when tire shopping.
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. Spanning the tire's circumference are deep grooves — called channels — that separate the tread.
The outer shoulder is the outermost section of the tire and is outside of 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 — it’s the tire's main contact point with the road. This is the area where the tread blocks are thickest and where you measure the tire tread depth.
Determining a tire’s tread depth involves measuring from the lowest point in the channel to the top of the tread on the contact patch.
This depth is important because the channels are responsible for shuttling water and slush away from the contact patch to maximize traction. If the tread isn’t deep enough, 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 main relatively simple ways to measure tread depth, but some are more precise than others.
If you look closely at the tire's channels, you'll notice small, raised bars that span the channels. 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.
A simple way to check tread depth is using the nickel or quarter test. 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 is covering the figurehead, you have a safe amount of tread remaining on the tire. 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.
The most official and accurate way to check tire tread is with a tire tread depth gauge. The tread depth gauge will have a blade side that looks similar to a flat-head screwdriver and a gauge side with either a manual gauge with measurement marks on it 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 channel 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 will allow you to compare your tire's tread depth to the requirements in your province.
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 that had 1.6 mm of tread took an extra 30.5 metres to stop from 112 km/h than the same vehicle equipped with tires that had 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.
Many variables come into play when shopping for a tire, but much of the research is already complete if you know what to look for.
Some shoppers simply follow the lead of the tire salesperson or mechanic who generally wants to sell the most expensive tire they can. Without a full understanding of how tires work, it’s easy to assume the priciest tire will last the longest. But this is't always the case.
A lot more goes into tire pricing than longevity. There are also special compounds that make the tire quieter, puncture resistant, or more stable in corners and braking.
If your main interest is a long-lasting tire, don't fall 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 tire's 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, you may see a premium $150 tire may have only a 300 treadwear rating but lots of other attractive features that drive up 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 the projected treadwear ratings.
Barring manufacturer defects, tires will last as long as they're supposed to, given your vehicle is in good mechanical condition and properly maintained. However, there are steps you can take 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 center of the tire to bulge, leading to excessive wear in the middle of the tire. Too little air can cause the center 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 in a vehicle 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.
Slippery driving conditions, like rain- or snow-slicked streets can lead to wheel-slip, which creates excess heat and wears out tires quickly. 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 make sure you 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 at all. 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 that have 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 no-risk guarantee that allows you to return the vehicle for a full refund within 10 days of receiving it. Beyond that, all Clutch vehicles come with 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.