How to Read a Tire Sidewall: Size, Load Index, Speed Rating and Markings
What every marking on a tire means: the size, load index and speed rating, XL and LT load range, M+S and 3PMSF, the DOT date code, UTQG and carmaker marks.
The side of a tire tells you almost everything you need to buy the right replacement. Here is how to read it, using 225/65R17 102H as the example.
The size: 225/65R17
- 225 is the section width in millimetres, measured across the widest point of the tire.
- 65 is the aspect ratio: the sidewall height as a percentage of the width. Here the sidewall is 65% of 225 mm, about 146 mm. A lower number means a shorter, sportier sidewall.
- R means radial construction, which almost every car tire uses. ZR is an older way of marking a high-speed radial.
- 17 is the wheel (rim) diameter in inches.
A P in front (P225/65R17) marks a P-metric passenger tire; LT marks a light-truck tire built for heavier loads. Off-road sizes such as 35X12.50R20LT are written in inches: 35″ tall, 12.5″ wide, for a 20″ wheel. People also type sizes as 225 65 17 or 2256517; they mean the same thing.
Not sure what else fits? The tire size calculator shows alternate sizes within 3% of the original diameter.
The service description: 102H
102 is the load index: the most weight each tire can carry at its maximum pressure. 102 means 850 kg per tire, or 3,400 kg for four. H is the speed rating: the highest speed the tire is certified for.
| Speed rating | Q | R | S | T | H | V | W | Y |
|---|---|---|---|---|---|---|---|---|
| Maximum km/h | 160 | 170 | 180 | 190 | 210 | 240 | 270 | 300 |
Replacement tires should match or exceed the load index and speed rating on your door placard. Winter tires are the one common exception: a lower speed rating is generally accepted on winter tires, as long as you respect it.
Load markings: XL and LT load range
XL (extra load, sometimes RF for reinforced) means a passenger tire built to carry more weight at a higher pressure than a standard-load tire of the same size. Your car needs XL if the placard calls for it.
Light-truck tires show a load range letter, the modern version of the old ply rating:
| Load range | C | D | E | F |
|---|---|---|---|---|
| Ply rating | 6-ply | 8-ply | 10-ply | 12-ply |
Winter markings: M+S and 3PMSF
M+S (mud and snow) only describes the tread pattern; many all-season tires carry it. The three-peak mountain snowflake (3PMSF) symbol means the tire passed a standard snow-traction test. It is the marking Quebec requires from December 1 to March 15, and the one Ontario insurers look for when giving a winter tire discount.
The DOT code and the tire’s age
The code starting with DOT identifies the factory and batch. Its last four digits are the week and year it was made: 2324 means the 23rd week of 2024. Rubber ages even when the tire is not used, so many carmakers recommend replacing tires after six to ten years, whatever the tread depth.
UTQG: treadwear, traction, temperature
Many tires sold in Canada also carry a US grading, for example 500 A A. Treadwear (500) compares wear against a reference tire: higher lasts longer, but only compare grades within one brand. Traction (AA, A, B, C) rates wet braking, and temperature (A, B, C) rates resistance to heat. Winter tires usually have no UTQG grade.
Other marks you may see
- Run-flat: RFT, ROF, SSR, ZP, DSST, EMT or MOE. See our run-flat guide.
- Carmaker marks: ★ (BMW), MO (Mercedes-Benz), N0 (Porsche), AO (Audi), T0 (Tesla) and others mean the tire was approved as original equipment. See OE tire markings explained.
- EV, Elect or HL: versions for electric vehicles or high-load sizes. See EV tires.
- Rotation arrow or Outside: directional or asymmetric tires that must be mounted a certain way.
Frequently asked questions
What does 225/65R17 mean on a tire?
225 is the width in millimetres, 65 is the sidewall height as a percentage of the width (about 146 mm), R means radial construction and 17 is the wheel diameter in inches.
What do the load index and speed rating mean?
The number after the size, such as 102, is the load index (102 = 850 kg per tire). The letter, such as H, is the speed rating (H = 210 km/h). Replacements should match or exceed the numbers on your door placard.
How do I tell how old my tires are?
Look at the last four digits of the DOT code: the first two are the week and the last two are the year. 2324 means the 23rd week of 2024.
What is the difference between M+S and the snowflake symbol?
M+S only describes the tread pattern. The three-peak mountain snowflake (3PMSF) symbol means the tire passed a snow-traction test, and it is what Quebec requires for winter.