That code on your sidewall — something like P235/65R17 102H — tells you everything about the tire’s size and ratings. Once you know what each part means, picking the right replacement is easy.
Breaking down 235/65R17
P (or LT): the type. “P” is passenger; “LT” is light truck (heavier-duty, for towing and hauling). No letter usually means metric passenger.
235: the section width in millimeters — the tire’s width from sidewall to sidewall.
65: the aspect ratio — the sidewall height as a percentage of the width. Lower number = shorter, sportier sidewall; higher = taller, more cushion.
R: radial construction (almost all modern tires).
17: the wheel diameter in inches the tire is built to fit.
The load index and speed rating
After the size you’ll see something like 102H. The number (102) is the load index — how much weight the tire can carry. The letter (H) is the speed rating — the max safe speed. Always match or exceed your vehicle’s original load index and speed rating.
Where to find your correct size
The easiest place is the sticker inside the driver’s door jamb (also in your owner’s manual) — that’s the manufacturer’s recommended size. The size on your current tires works too, unless someone sized up or down before you.
Changing wheel diameter or width? Then your tire size has to change to match, and getting offset and overall diameter right matters — a local shop can spec it so your speedometer stays accurate and nothing rubs.
Frequently asked
Can I put a different size tire on my car?
You can change sizes, but the overall diameter should stay close to stock to keep your speedometer accurate and avoid rubbing. Plus-sizing (bigger wheel, shorter sidewall) keeps diameter the same. A shop can confirm what fits.
What does the letter before the size mean?
“P” means passenger tire; “LT” means light truck — built tougher for towing and heavier loads. Use the type your vehicle calls for.
Keep reading
Last updated 2026-06-27. General guidance only — confirm specifics with a local shop for your exact vehicle.