When to put winter tires on in Ontario: the 7°C rule, not the first snow

When should you actually switch?

Put your winter tires on when daytime highs are consistently near 7°C. Around Puslinch, Guelph and Cambridge, that's usually the back half of October, and it has nothing to do with snow.

The practical trigger is simpler than a forecast. When you start grabbing a jacket to walk out to the car in the morning, and you're still wearing it at lunch, your all-seasons are already past their useful temperature range. That's your signal.

A few things that make the timing easier:

• Check the ten-day forecast in mid-October. Once you see highs stuck in single digits, book.
• Overnight lows drop first. A 2°C morning with a 14°C afternoon means you're close, not there.
• If you drive early, before 7 a.m., you're on the coldest pavement of the day. Switch on the early side.
• Come spring, the same rule runs backwards. Most people around here change back in early to mid-April.

Why 7 degrees and not the first snow?

Because rubber is the whole story. All-season compounds are built to work across a wide temperature band, and the low end of that band is roughly 7°C. Below it the rubber stiffens, the tread stops conforming to the road surface, and your braking distance grows even on clean dry asphalt.

Winter compounds are softer and stay flexible in the cold. That's why the difference shows up on a clear 3°C morning on the 401, not just in a snowbank. Cold dry pavement is where you'll feel it first, in how quickly the car settles when you get on the brakes.

The tread pattern helps too. All those tiny slits across the blocks, called siping, open up and bite into snow and slush, and the deeper grooves clear water instead of skating over it. But the compound is doing most of the work on cold dry pavement, which is where most of your winter kilometres actually happen.

Waiting for snow means you spend three or four weeks driving on rubber that's already gone hard. It's not dramatic. You just have less margin than you think you do when someone stops short in front of you on Brock Road.

Are winter tires mandatory in Ontario?

No. Ontario doesn't require winter tires. Quebec does, from December 1 to March 15, and if you're driving to Montreal or the Laurentians in winter you need them on the car to cross the border legally.

Here, the law only cares that your tires are roadworthy: enough tread, no exposed cord, no serious damage. Beyond that, it's your decision.

And that decision genuinely depends on how you drive. Someone who parks the car most of the winter, drives to Aberfoyle and back, and puts on 3,000 km a year is in a different position than someone commuting Puslinch to Milton on the 401 every morning in the dark. The commuter is on cold pavement twice a day, in traffic, at highway speed. That's the case where winters pay for themselves in one avoided panic stop.

If you're honestly in the low-kilometre group and your all-seasons have good tread, you can skip it. Plenty of people around here get by without winters and always have.

The winter tire insurance discount nobody applies for you

Since January 2016, every auto insurer in Ontario has been required to offer a winter tire discount. It's typically 2–5% off your annual premium, and on most policies that covers a meaningful chunk of the changeover cost.

The catch is in the details, and the details vary by insurer.

The eligibility window is not standard. Some insurers want the tires on the car from November 1 to April 1. Others use November 20 to April 15. Others require December 1 to March 31. If you switch late, or take them off early in a mild March, you can fall outside your own insurer's window without realizing it.

It usually isn't automatic. Insurers don't know what's on your car. Many require you to declare it, and some ask for proof.

So, three things to do before you book:

1. Call your insurer or broker and ask two questions: what's the exact discount, and what are the exact dates I need the tires on?
2. Tell them you're running four winter tires. Get it noted on the policy.
3. Keep the changeover invoice. It shows the date and the tires, which is the proof most insurers accept. Take a photo of the sidewall too, so the snowflake symbol is on record.

One more thing worth knowing: most insurers require a full set of four to qualify. A pair on the drive wheels usually doesn't count.

Why two winter tires is worse than none

Mixing grip front-to-rear makes the car unstable exactly when you need it stable. Whichever end has less grip lets go first, and you don't get to choose when.

Put winters on the front of a front-drive car and it pulls away from a stop beautifully. Then you brake hard into a cold corner and the rear, still on hardened all-seasons, breaks loose and starts coming around. That's a spin, and it happens faster than most drivers can correct.

Winters on the rear only fails the opposite way. Now the front goes first, so you turn the wheel and the car keeps going straight toward whatever you were steering away from.

Four matching tires means the car does roughly what you expect it to do, which is the only thing you're really buying. Always four.

What does a changeover involve, and what does it cost?

There are really two different jobs here, and that's why quotes differ so much. Both are part of what we do on the tires side.

Tires already mounted on their own rims. This is the quick one. Four wheels off, four wheels on, torqued properly, pressures set. If your car has tire pressure sensors in the winter wheels, they may need a quick reset. Least labour, lowest cost. Over three or four seasons, a second set of rims usually pays for itself in labour alone.

Tires off the rims. Now each wheel has to be unmounted, the winter tire mounted, and the assembly balanced. Sensors often need attention because the valve and sensor come apart during the swap. More steps, more time, higher cost. It's also harder on the tire bead over many seasons.

Storage is the other variable. If you don't have room in the garage for four tires, some shops store them for a seasonal fee.

When are your winter tires done?

Check three things before you haul the set out of the garage.

Tread depth first. New winter tires start around 10–11 mm. Once you're down near 4 mm, the snow and slush performance falls off badly, even though the tire is still legal. The wear bars moulded into the grooves are the last-call marker, not the retirement point for a winter tire.

Then cracking. Look at the sidewall and between the tread blocks. Fine cracks that look like dried mud mean the rubber has aged out.

Last, the date code. On the sidewall there's a four-digit number after "DOT" and some other characters. First two digits are the week, last two are the year. So 3419 means the 34th week of 2019. A six- or seven-year-old set can have plenty of tread left and still be hardened enough that it's lost most of the advantage you bought it for.

If the set checks out on all three, run it another season. That's a real answer, not a stalling tactic, and any shop worth calling will give you the same one.

Frequently asked questions

Can I just leave winter tires on all year?

You can, but they'll wear out fast. Above about 7°C the soft compound scrubs away quickly, and handling gets vague in warm weather. Most people get two or three winters out of a set that stays on seasonally, and considerably less than that if it runs through July.

Do all-weather tires count for the insurance discount?

Usually yes, if they carry the three-peak mountain snowflake symbol on the sidewall. That symbol is what insurers look for, not the words all-weather. Check the sidewall, then confirm with your insurer before you assume.

Does my all-wheel-drive SUV need winter tires?

All-wheel drive helps you go. It does nothing for stopping or turning, and those are the two things that put cars in the ditch. An AWD vehicle on all-seasons in February stops no better than a front-drive car on the same rubber.

What tire pressure should I run in winter?

Whatever the sticker in your driver's door jamb says, checked in the cold. Pressure drops roughly 1 PSI for every 5°C the temperature falls, so a set that was perfect in September will read low by November. Check it monthly through the winter.

Book before the late-October rush

Everyone calls the same week the temperature drops. If you call in early October you pick a time that suits you. If you call the day after the first cold snap, you're often looking at a wait of a week or two, and you spend that time driving on hardened rubber.

Bring your year, make and model, and say whether the tires are on their own rims. We'll give you a firm number and a slot. If you'd rather wait and watch the thermometer, that's fine too. Watch for a run of days topping out near 7°C, then call.

We've been doing this off the 401 at Brock Road since 2008, and the changeover weeks are the same every year.