Tread depth: recommendation vs legal minimum
Tread depth in Canada is usually measured in 32nds of an inch. The legal minimum in Ontario is 1.5 mm (just under 2/32 in), but wet, slush and snow grip falls off long before that.
As a recommendation, replace winter tires at about 5/32 in (about 4 mm), because snow traction drops sharply below that level. Many drivers replace all-season tires at around 4/32 in (about 3 mm) for the same reason in heavy rain.
- Winter tires: replace at about 5/32 in (about 4 mm) (recommended).
- All-season and all-weather tires: consider replacing at about 4/32 in (about 3 mm).
- Any tire: 1.5 mm is the legal minimum in Ontario, not a safe target.
How to check it
A tread depth gauge is cheap and accurate. Measure in the inner, centre and outer grooves of each tire. Every tire also has small raised wear bars in the main grooves at about 2/32 in (1.6 mm); when the tread is flush with them, the tire is at the end of its life. A coin can give a rough idea, but a gauge is the only reliable reading.
If the readings across one tire are very different, the tire is wearing unevenly, usually due to pressure, alignment or balance issues. See why tires wear unevenly.
Age: read the DOT date code
Rubber hardens with age, even on a tire that's rarely driven. The last four digits of the DOT code on the sidewall are the week and year of manufacture: 2419 means the 24th week of 2019.
Many tire and vehicle manufacturers recommend a close annual inspection once a tire is about five or six years old, and replacement at no more than ten years regardless of tread. Check your vehicle and tire manufacturer's guidance for the exact figures.
Damage that means replacement
Some damage can't be safely repaired:
- A bulge or bubble in the sidewall (indicating broken internal structure).
- Cracks deep enough to see into, or exposed cords or steel.
- A puncture in the sidewall or shoulder, or a hole larger than about 6 mm (¼ in).
- A tire that was driven flat and is damaged inside.
Vibration, noise and pulling
A new vibration at highway speed, a rhythmic hum or a car that pulls can point to a tire problem (such as a separated belt, cupping, or internal damage), but it can also stem from improper balance or alignment. It's worth having it checked before deciding the tires are done. Many punctures in the tread can be fixed; see flat tire repair.
Two tires or four?
If you replace only two, put the new tires on the rear axle on most vehicles, so the rear doesn't lose grip first in the wet. On all-wheel-drive vehicles, many manufacturers require all four tires to be within a small difference in tread depth to protect the drivetrain; check your owner's manual.
When it's time, our tire brands and prices page explains the three price tiers and what an installed price includes.
