Open the driver's door and check the placard on the door jamb — your factory tire size is printed there, and the same size is moulded into the sidewall of every tire. A size like 225/65R17 reads: 225 mm of tread width, a sidewall that is 65% as tall as the tire is wide, R for radial construction, on a 17-inch rim. Not sure? Text a photo of the placard to (905) 475-2104 and we'll look it up for you.
What every number in 225/65R17 102H means
Take a common size, 225/65R17 102H, one piece at a time:
- 225 — section width in millimetres, roughly how wide the tread is;
- 65 — aspect ratio: the sidewall's height as a percentage of the width, about 146 mm here. A lower number means a shorter, sportier sidewall;
- R — radial construction, which is virtually every passenger tire made today;
- 17 — rim diameter in inches: the wheel this tire fits;
- 102 — load index, a code for how much weight each tire is rated to carry;
- H — speed rating, the tire's certified sustained-speed capability.
When you replace tires, match the size and choose a load index and speed rating that meet or exceed what the placard shows.
Trust the placard, not the tires on the car
The placard is what the factory specified for your exact vehicle. The tires on the car right now are only whatever the last person bought — and previous owners get it wrong more often than you'd think. A wrong size can ride around unnoticed for years, so when the placard and the sidewall disagree, the placard wins.
Or skip the decoding entirely. Pick your make, year and model in our tire finder and we show the factory sizes, or go straight to the by-vehicle pages and jump to your car. Prefer a human? Call or text a photo of the placard to (905) 475-2104 — we've been matching tires to cars in Markham since 1978.
LT, staggered and minus-sizing — the three exceptions
- LT prefix. LT245/75R17 means Light Truck construction — built for heavier loads on trucks and full-size vans. If your placard says LT, replace with LT; a passenger tire in the same size is not the same tire.
- Staggered fitments. Some vehicles — often performance and rear-drive models — run wider tires on the rear than the front. The placard lists both, and it also limits how the tires can be rotated.
- Minus-sizing for winter. Winter tires often go one rim size down on a separate set of rims — a smaller wheel with a taller sidewall that keeps the same overall diameter. It has to be worked out per vehicle, so ask us what's safe for yours before buying.
Reading the placard, step by step
- Open the driver's door and look at the door jamb — the tire placard is a printed label, usually near the latch or along the door edge.
- Find the tire size line — it looks like 225/65R17. Some placards also list a smaller size for the compact spare; ignore that one.
- Check whether front and rear are listed separately. Two different sizes means a staggered fitment — write down both.
- Note the service description after the size — e.g. 102H. That is the load index and speed rating your replacement tires should match.
- Snap a photo. Bring it in, or text it to (905) 475-2104 and we'll quote the right tires straight from it.
Common questions
Can I put a different size on my car?
Sometimes, within limits — but size changes affect speedometer accuracy, clearance and handling, and the load index still has to be covered. The placard size is always the safe default. Call or text us with what you have in mind before buying.
My placard shows different sizes front and rear — is that normal?
Yes — that is a staggered fitment, common on performance and rear-drive vehicles. Buy each axle its listed size, and expect rotation options to be limited.
Where do I find my size if the placard is worn or missing?
The owner's manual lists the factory sizes, and the by-vehicle finder on our tires page shows them for your make, year and model. Or text a photo of the sidewall to (905) 475-2104 and we'll verify it against your vehicle.
Does the letter before the numbers matter, like P or LT?
Yes. P (or no letter) means a passenger tire; LT means Light Truck construction rated for heavier loads. If your placard says LT, replace with LT — a passenger tire in the same size is not a substitute.
Questions about your own car? Bring it to the counter — straight answers, all-in prices, same-day when the schedule allows.
Updated 2026-08-11 · Taylor Tire, Markham