What do the numbers in a tire size mean?
The first number is the width in millimeters, the second is the aspect ratio, and the last number is the wheel diameter in inches.
Take 205/55R16. The tire is 205 mm wide from sidewall to sidewall. The 55 means the sidewall height is 55% of that width, about 113 mm. The 16 means it fits a 16 inch wheel.
A lower aspect ratio means a shorter sidewall. A 45 series tire has a much thinner profile than a 70 series tire of the same width.
What does the R mean on a tire?
The R means radial construction, where the internal cord plies run across the tire from bead to bead.
Almost every passenger and SUV tire sold today is radial. You may see a D for diagonal (bias-ply) on some trailer or specialty tires, but you will rarely see it on a car.
What do the load index and speed rating mean?
The load index is the number after the size, and it tells you how much weight each tire can carry at its maximum pressure. The speed rating is the letter after it, and it tells you the top sustained speed the tire is rated for.
In 91V, 91 means 1,356 lb per tire and V means 149 mph. Other common ratings are S (112 mph), T (118 mph), H (130 mph) and W (168 mph).
When you replace a tire, match or exceed both the load index and the speed rating on your vehicle placard. A higher rating is fine. A lower one is not.
What is the difference between P-metric and LT tires?
P-metric tires are passenger tires, and LT tires are light-truck tires built to carry heavier loads at higher pressures.
A size like P225/65R17 is P-metric. A size with no letter in front, like 225/65R17, is usually a Euro-metric passenger tire, which is treated much the same way. A size like LT265/70R17 is a light-truck tire, and LT tires also carry a load range letter such as C, D or E.
Use the type your placard calls for. Do not put a passenger tire on a vehicle that specifies LT tires.
Where do I find the right tire size for my car?
Look at the tire placard on the driver’s door jamb, or check your owner’s manual.
The placard lists the original size, load index, speed rating and recommended cold tire pressure. The size printed on the tires already on your car may be different if a previous owner changed it, so the placard is the better source.
Send us a photo of the placard or the sidewall and we can read it with you.
How do I read the date on a tire?
Find the DOT code on the sidewall. The last four digits are the week and year the tire was made.
For example, 3220 means the 32nd week of 2020. The full code is sometimes printed only on one side, so check the inner sidewall if you do not see it.
Quick answers
Can I use a different tire size than the one on my placard?
Sometimes, but it has to be checked for your specific vehicle. A common rule is to keep the overall diameter within about 3% of the original and match or exceed the load index and speed rating.
What does 91V mean on a tire?
It is the service description. 91 is the load index, meaning 1,356 lb per tire, and V is the speed rating, meaning 149 mph.
Does tire width affect anything besides fit?
Yes. Width changes how the tire fits in the wheel well and on the wheel, and it can change how the car handles. Always confirm a width change for your vehicle first.
Can you find my tire size if I send a photo?
Yes. Text us a clear photo of the sidewall or the door jamb placard and we will read the size and check what used tires we have.