How to Read Tire Size
A simple guide with examples
The numbers on your tire sidewall look like a secret code — but they're actually simple once you know what each part means. Here's how to read your tire size so you can shop for the right tires with confidence.
Where to Find Your Tire Size
Your tire size is printed on the sidewall of every tire — the part facing outward when mounted. Look for a sequence like 205/55R16 or 225/45R17.
You can also find it in three other places:
- —The driver's door jamb sticker (open the driver door, check the frame)
- —Your vehicle owner's manual
- —The glove box lid on some vehicles
Breaking Down the Numbers: 205/55R16
Let's decode the most common format you'll see:
205/55R16
Common Tire Sizes in Ottawa
These are the sizes we see most often at our shop:
| Tire Size | Common On | Category |
|---|---|---|
| 205/55R16 | Honda Civic, Toyota Corolla, Mazda3 | Compact |
| 225/65R17 | Toyota RAV4, Honda CR-V, Ford Escape | Compact SUV |
| 235/60R18 | Hyundai Tucson, Nissan Rogue, Subaru Outback | Mid-size SUV |
| 245/45R19 | BMW 3 Series, Audi A4, Tesla Model 3 | Performance |
| 275/55R20 | Ford F-150, RAM 1500, GMC Sierra | Truck |
What About the Letters Before the Numbers?
Sometimes you'll see a letter prefix before the width:
- —P (e.g., P205/55R16) — Passenger vehicle. Most common, often omitted.
- —LT (e.g., LT245/75R16) — Light Truck. Built for heavier loads, common on pickups and vans.
- —ST (e.g., ST205/75R15) — Special Trailer. Only for trailers, never on driving vehicles.
Aspect Ratio: Why It Matters
The aspect ratio (the second number) tells you how tall the sidewall is relative to the width. A lower number means a thinner sidewall:
- —55–65 — Standard comfort. More cushion, quieter ride. Most sedans and SUVs.
- —45–50 — Sport-oriented. Better handling, slightly firmer ride.
- —35–40 — Low profile. Maximum performance, but more road feel and pothole risk.
At Techtire, low-profile tires (40 and below) require extra care during mounting, which is why our installation pricing has a separate tier for them.
Low-profile tires (35–40 aspect ratio) look great but take a beating on Ottawa roads. The thin sidewall offers less cushion against potholes, which means more bulges, more bent rims, and more unexpected replacements. If you park outside and drive city streets, a 50–55 aspect ratio is a better long-term value.
Can I Use a Different Tire Size?
Short answer: stick with your manufacturer-recommended size. Using the wrong size can affect:
- —Speedometer accuracy
- —ABS and traction control calibration
- —Fuel efficiency
- —Ride comfort and handling
If you want to go up or down a size (for example, fitting winter tires on smaller rims), talk to us first. We can tell you which alternate sizes are safe for your vehicle.
How to Use Your Tire Size to Shop
Once you know your size, you can:
- 01Check our inventory — use our tire estimator to see what we have in stock for your exact size
- 02Compare prices — see per-tire and full-set pricing with installation included
- 03Book online — pick your tires, choose a time, and we handle the rest
Check our prices in seconds.
Enter your tire size and see what we have in stock — with instant per-tire and full-set pricing.