When to replace tires
Replace a tire when the tread is level with the wear bars at about 1.6 mm, when the sidewall is bulging or the cord is showing, or when the tire maker’s age guidance says it is time. There is no single kilometre limit.
Updated
Tread wear bars are the built-in limit
Tires have wear indicator bars molded into the main grooves. They sit at about 1.6 mm (2/32 inch). When the tread is level with those bars, the tire is worn out. Replace it. Do not wait for a blowout or for the belts to show.
There is no honest single mileage at which every tire needs replacing. Wear depends on the tire, the vehicle, alignment, pressure, and how it is driven.
Damage that means the tire should come off
Replace a tire with a bulge or bubble in the sidewall, cord or belt showing through the rubber, a cut deep enough to show the body, or tread that is separating. A bulge means the structure has failed.
A puncture in the tread can sometimes be repaired from the inside with a proper patch-and-plug. A repair in the sidewall, or a string plug left as the only repair, is not something to keep driving on. Ask the shop what kind of repair they would do, and follow the tire maker’s repair limits.
If the tire keeps losing pressure and the cause is not a valve or a bead that can be reseated, treat it as damaged until someone inspects it off the car.
Uneven wear is a reason to look at more than the rubber
Tread worn on one shoulder, or cupped around the tire, usually means inflation, alignment, or a worn suspension part. Replacing the tire without correcting that will wear the next tire the same way. A shop can measure it. Tire-Finder does not rank shops and does not show star ratings.
Age matters even when tread is left
Rubber hardens with time. Many tire makers suggest having tires inspected around five years from the manufacture date and replacing them by about ten years even if tread remains. Some brands recommend an earlier cutoff, including around six years. That is brand guidance, not a Canadian law.
Read the date from the DOT code on the sidewall. The date is the week and year the tire was made, not the day it was installed.
Common questions
Is there a kilometre count that means a tire must be replaced?
No. Tires do not expire at one mileage. Use the wear bars, look for damage, and follow the age guidance from the tire maker.
Should winter tires be replaced at the same depth as summer tires?
The wear bars are still about 1.6 mm, but snow traction drops before that. Many tire makers suggest replacing winter tires around 4/32 inch (3.2 mm) of tread. That is a recommendation, not one national legal limit.