Enter your OEM tire size, your placard PSI, and your province. We'll show winter-compatible sizes within the safe ±3% diameter band, your cold-weather pressure table from -30 °C to +25 °C, and your province's swap-window rules.
Not mandated by Ontario law, but most insurers offer a winter-tire discount and many manufacturers' AWD systems are calibrated to assume them. Install by early November, remove once daytime temperatures stay above 7 °C.
| Size | Type | Diameter | Δ vs OEM |
|---|---|---|---|
| 225/65R17 | OEM Original size. Match for warranty replacement. | 724 mm | +0.00% |
| 215/70R17 | Minus-one Narrower tread cuts through snow better. Most popular winter swap. | 733 mm | +1.17% |
| 195/75R17 | Alternate Alternate size within the safe ±3% diameter band. | 724 mm | +0.00% |
| 205/70R17 | Alternate Alternate size within the safe ±3% diameter band. | 719 mm | -0.76% |
| 215/65R17 | Alternate Alternate size within the safe ±3% diameter band. | 711 mm | -1.79% |
| 185/75R17 | Alternate Alternate size within the safe ±3% diameter band. | 709 mm | -2.07% |
Always match or exceed the OEM load index and speed rating. Confirm fender clearance for wider sizes. Suggestions are based on overall-diameter math only — not a substitute for a fitter at the shop.
| Outside temp | PSI | Δ |
|---|---|---|
| -30 °C | 24.1 | -8.9 |
| -25 °C | 25.0 | -8.0 |
| -20 °C | 25.9 | -7.1 |
| -15 °C | 26.8 | -6.2 |
| -10 °C | 27.6 | -5.4 |
| -5 °C | 28.5 | -4.5 |
| 0 °C | 29.4 | -3.6 |
| +5 °C | 30.3 | -2.7 |
| +10 °C | 31.2 | -1.8 |
| +15 °C | 32.1 | -0.9 |
| +20 °C | 33.0 | 0.0 |
| +25 °C | 33.9 | +0.9 |
Reference: 33 PSI at 20 °C. Tire pressure changes ≈1 PSI per 5.6 °C. Always set cold (vehicle parked ≥3 hrs).
Diameter (mm) = rim × 25.4 + 2 × width × aspect / 100. We only suggest sizes whose total diameter is within ±3% of OEM, the industry-standard safe band for speedo accuracy and fender clearance.
Drop the section width by 10 mm and bump the aspect ratio one notch to keep the same diameter. Narrower tread cuts through snow; taller sidewalls cushion potholes; smaller (cheaper) steel rims are easier to dedicate to a winter-only set.
Tire pressure tracks ambient temperature at constant volume. Set placard PSI cold at the bay, and the tool projects PSI from -30 °C to +25 °C so you know what to expect on a Canadian morning.
A 2019 Honda CR-V wears 235/65R17 from the factory — overall diameter ≈ 737 mm. The most popular winter swap is the 225/65R17 minus-one (10 mm narrower, same rim, ~722 mm diameter, just inside the −3% band) on dedicated steel wheels. At 33 PSI set in the bay at +20 °C, expect the same tires to read about 26 PSI on a -20 °C morning — re-inflate to 33 PSI cold every cold snap.
Not mandated by Ontario law, but most insurers offer a winter-tire discount and many manufacturers' AWD systems are calibrated to assume them. Install by early November, remove once daytime temperatures stay above 7 °C.
Quebec is the only province where winter tires are mandatory province-wide. Under §440.1 of the Quebec Highway Safety Code, every passenger vehicle on Quebec roads must wear tires bearing the three-peak mountain snowflake (3PMSF) pictograph from December 1 through March 15 inclusive. Fines start at $200–$300 per offence. British Columbia requires winter (3PMSF) or M+S tires on designated highways from October 1 through April 30; the rule is enforced via signage, not province-wide. The other provinces strongly recommend installation by Hallowe'en and removal in mid-April, but do not legally mandate it.
Overall diameter is the actual outside diameter of an inflated tire, calculated as rim diameter (in mm) plus twice the sidewall height. Going more than about ±3% from the OEM diameter throws off your speedometer, your traction control, and your fender clearance. Industry consensus (Tire Rack, Toyo, etc.) is to stay inside ±3%. Our calculator only suggests sizes within that band.
A minus-one winter fitment narrows the tread by 10 mm and raises the sidewall to keep the same overall diameter. The narrower contact patch cuts through snow to find pavement (instead of riding on top of it), the taller sidewall absorbs potholes, and the smaller wheel diameter usually means cheaper steel rims for a winter-only set. Example: a 225/65R17 OEM becomes a 215/70R17 winter — same diameter, narrower tread, taller sidewall.
Tire pressure rises and falls with temperature at constant volume. The standard rule is roughly 1 PSI per 10 °F (≈ 5.6 °C) of ambient air-temperature change. So a tire set to 33 PSI at +20 °C in the bay will read about 26 PSI on a -20 °C morning — well below safe and a TPMS-warning trigger. Always set pressures cold, ideally first thing in the morning before driving, and re-check every time the temperature drops 10 °C.
Dedicated winter tires (e.g. Bridgestone Blizzak, Michelin X-Ice, Nokian Hakkapeliitta) outperform all-weather tires below -10 °C and on packed snow or ice. All-weather tires that carry the 3PMSF symbol (Michelin CrossClimate, Nokian WR, Toyo Celsius) are a reasonable compromise for milder Canadian climates (coastal BC, southern Ontario) where temperatures rarely stay below -10 °C for long. They legally satisfy Quebec's §440.1. For Prairie or Northern winters, dedicated winters are still meaningfully safer.
The industry rule of thumb is 7 °C: when daytime highs consistently sit at or below 7 °C, summer-tire compounds harden and lose grip. In most of Canada that's late October to early November. Swap back when overnight lows stay above 7 °C in spring (mid-April for most of the country, late April in the Maritimes).
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