How Do You Know When Winter Tires Are Worn Out?

A winter tire stops working as a winter tire long before it hits the legal 1.6mm limit. Check tread depth on all four, check the inside edge by hand, and check the build date on the sidewall. Past five years old, age matters more than tread.

Winter tires are not mandatory in New Brunswick, but if you run them, the fall changeover is the moment to make this call. Finding out in January that the set is finished means buying tires in the worst month to buy tires.

What tread depth do winter tires need?

More than the legal minimum. New Brunswick's inspection standard sets 1.6mm, or 2/32 of an inch, as the fail line for any tire. That is a legal floor, not a winter performance standard. A winter tire relies on deep tread and biting edges to move snow and slush, and both of those disappear as the tire wears.

Source: New Brunswick Official Vehicle Inspection Station Manual

Why winter tires need more tread than the law requires

• Deep grooves give snow and slush somewhere to go. A shallow tread packs and stops clearing
• Sipes, the fine slits across the tread blocks, are the biting edges that grip ice. They get shallower as the tire wears
• A worn winter tire still has a soft compound, so it feels fine on dry pavement and then does not perform when it matters
• On a legal-but-worn winter tire you are paying winter tire money for all-season performance

How do you check if your winter tires are done?

Measure the tread on all four, feel the inside edge by hand, look for cracking, and read the build date on the sidewall. Tread wears unevenly, alignment problems hide on the inner face, and rubber can harden or crack while tread looks fine. Any one of the four can end the tire's life on its own, so check all four.

The four checks, in order

1. Tread depth, all four tires. Use a gauge. Measure in more than one groove and in more than one spot around the tire, because wear is rarely even.
2. The inside edge. Run your hand along the inner face of the tread. This is where alignment wear hides, and it is invisible from where you park.
3. Cracking. Look between the tread blocks and along the sidewall for fine cracks. That is the rubber going.
4. Build date. The last four digits of the DOT code are the week and year. 3223 means the 32nd week of 2023.

The check that catches the most people is the inside edge. A tire can look completely fine from the side and be bald on the inner face where you never look. That is an alignment problem eating the tire from a side you cannot see, and we get customers coming in with a flat who had no idea their tire was bad. Put your hand on the inside of the tread and feel it. The other one is the year. Check the year on the tire every single time. Past five years old you start getting dry rot no matter how much tread is left, and once a tire is dry rotting we recommend replacing it as soon as possible.

Does the age of a winter tire matter more than the tread?

Often, yes. Winter grip comes from a compound that stays soft in cold weather, and rubber hardens as it ages. A five-year-old winter tire with good tread can be noticeably worse on a cold morning than a newer tire with less tread, because the compound has gone stiff.

What causes a tire to age badly

• Heat. A set stored somewhere hot cooks over the summer
• Moisture. Damp storage is hard on rubber
• Sunlight. UV breaks down the compound
• Time. It happens even to a tire that is never driven

Storage is the part you control. Keep off-season tires somewhere cool, dry, and out of direct sun, and they last longer than a set thrown in a hot shed. Note that we do not offer tire storage, so this is on you or wherever you keep them.

Should you replace all four winter tires or just the worn ones?

All four. Mixing a worn pair with a new pair gives one end of the vehicle more grip than the other, which produces uneven braking and makes the low-grip end break away first in a corner. On an all-wheel-drive vehicle it also creates rolling diameter differences that strain the drivetrain.

This is the same reason two winter tires and two all-seasons is a bad setup. Balanced grip at all four corners matters more than the absolute grip level at any one of them.

When should you check?

Now, before the changeover rush. The calls start picking up in September and October is the peak. Finding out in September that your winter set is finished means you have time and stock. Finding out in November means taking whatever is left.

Book an off-rim tire change online, call (506) 248-6006, or drop in at 300 Wilsey Road #1. We are open seven days a week, Monday to Saturday 9 to 7 and Sunday 9 to 5. If you just want your winter set looked at before you commit to anything, bring it in and we will tell you straight.

Key takeaways

• 1.6mm is the legal minimum for any tire, not a winter performance standard.
• Winter tires lose their snow and ice grip well before they reach the legal limit.
• Check tread on all four, the inside edge by hand, cracking, and the build date.
• Past five years, age and dry rot matter regardless of remaining tread.
• Storage conditions decide how well a set survives the off-season.
• Replace all four together. Mixing worn and new unbalances the vehicle.

Frequently asked questions

How many seasons do winter tires last? It depends far more on kilometres and storage than on seasons. A set driven lightly and stored properly can go several winters. A set left on through summer heat or stored somewhere hot and damp can be finished much sooner. Check tread and age each fall rather than counting winters.

Is the legal tread limit good enough for winter tires? No. 1.6mm is the legal minimum for any tire in New Brunswick, and a winter tire at that depth has lost most of what makes it a winter tire. The tread depth and the biting edges are what move snow and slush. Judge a winter tire well before it reaches the legal line.

Can old winter tires be dangerous even with tread left? Yes. Winter grip comes from a soft compound, and rubber hardens with age. A tire past five years old can look fine and still be noticeably worse in cold weather. Check the last four digits of the DOT code on the sidewall for the build week and year.

Should I replace all four winter tires at once? Yes. Mixing worn and new tires means one end of the car grips better than the other, which causes uneven braking and sliding. On all-wheel drive it also creates rolling diameter differences that strain the drivetrain. Four matching tires, always.