How do I tell how old a tire is?

Four digits, since 2000: the first two are the week of the year (01 to 53) and the last two are the year. 2519 is the 25th week of 2019. 0824 is the 8th week of 2024.

What is the difference between M+S and the snowflake symbol?

M+S, M&S or M/S means mud and snow, and it is awarded on TREAD GEOMETRY alone. No tire is driven on snow to earn it and no performance is measured. Most all season tires carry it. It is a description of a tread pattern, not a winter capability. The three peak mountain snowflake is earned by testing. The tire has to deliver at least 110 percent of a reference tire's traction on medium packed snow, which is a 10 percent margin over the baseline, before it may carry the symbol. That is a real threshold, and it is why the symbol and M+S are not interchangeable.

Do all tires carry UTQG grades?

No. The grades are required on passenger tires sold in the United States, and several categories are exempt, including deep tread light truck tires, winter tires, temporary spares, trailer tires and tires under 12 inches. An absent grade is not a defect.

What every marking on a tire sidewall means

Four unrelated marking systems share the same piece of rubber, each with its own authority and its own failure mode when it is misread. Here is what each one actually says.

The size and what follows it

Decode a size - section width, aspect ratio, construction and rim diameter, with the dimensions they imply.
Service type prefixes - P, LT, ST, T, C, and what no prefix at all means.
Load index - the number after the size, and the mass it stands for.
Speed symbol - the letter after the load index, including ZR, W, Y and (Y).

DOT code and date code

How old the tire is. A four digit code is week and year; a three digit code is week and one digit of the year, with no way to tell the decade.

The date code is only required on one sidewall. Find DOT on one side with no date after it and you are looking at the wrong side of the tire - check the other one before concluding the tire is unmarked.

Read the detail

UTQG: treadwear, traction, temperature

Three grades set by a federal regulation, each measuring something narrower than it sounds.

A comparative number, not a mileage. A tire graded 200 wore at half the rate of a tire graded 100 on the government test course under test conditions. It is not a promise of twice the miles, and it is not comparable across brands with confidence: manufacturers run their own tests and assign their own grades, and are only forbidden from overstating them. Treat it as a within-brand comparison and nothing more.

Read the detail

Load range letters and ply ratings

The letter on a light truck tire, and the ply rating equivalent it stands for.

The ply rating is an equivalence, not a count. A load range E tire is not built from ten plies; it is built to the strength ten plies of the old cotton cord construction gave. Counting layers in a cut tire will not produce this number.

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M+S against the three peak mountain snowflake

One is awarded on tread shape. The other has to be earned in a snow traction test.

M+S, M&S or M/S means mud and snow, and it is awarded on TREAD GEOMETRY alone. No tire is driven on snow to earn it and no performance is measured. Most all season tires carry it. It is a description of a tread pattern, not a winter capability.

Read the detail

Common questions

How do I tell how old a tire is?: Four digits, since 2000: the first two are the week of the year (01 to 53) and the last two are the year. 2519 is the 25th week of 2019. 0824 is the 8th week of 2024.
What is the difference between M+S and the snowflake symbol?: M+S, M&S or M/S means mud and snow, and it is awarded on TREAD GEOMETRY alone. No tire is driven on snow to earn it and no performance is measured. Most all season tires carry it. It is a description of a tread pattern, not a winter capability. The three peak mountain snowflake is earned by testing. The tire has to deliver at least 110 percent of a reference tire's traction on medium packed snow, which is a 10 percent margin over the baseline, before it may carry the symbol. That is a real threshold, and it is why the symbol and M+S are not interchangeable.
Does the DOT code appear on both sides of the tire?: The date code is only required on one sidewall. Find DOT on one side with no date after it and you are looking at the wrong side of the tire - check the other one before concluding the tire is unmarked.
Do all tires carry UTQG grades?: No. The grades are required on passenger tires sold in the United States, and several categories are exempt, including deep tread light truck tires, winter tires, temporary spares, trailer tires and tires under 12 inches. An absent grade is not a defect.

Where these figures come from

Published values here were read from 12 independent sources:

49 CFR 575.104 - Uniform tire quality grading standards - Legal Information Institute, Cornell Law School, current text read 27 August 2026 (read 2026-08-27)
Traction grade adhesion coefficients, traction and temperature grade definitions, treadwear grading procedure
Uniform Tire Quality Grading - Wikipedia, revision read 27 August 2026 (read 2026-08-27)
Traction grade g force table, temperature grade speeds, treadwear grade meaning and limits
UTQG Ratings Explained - TireGrades, updated 9 March 2026 (read 2026-08-27)
Traction grade g force table, temperature grade speeds, treadwear self reporting
UTQG - How to Read a Sidewall - Yokohama Tire, undated manufacturer reference (read 2026-08-27)
Temperature grade speeds, which tire categories are exempt from UTQG marking
Understanding DOT Codes: Guide to Tire Identification - Wheel-Size.com, undated reference article (read 2026-08-27)
DOT code structure, plant code width, omitted letters, date code format and which sidewall carries it
5 Tips to Read the DOT Date Code - Tires Easy, undated reference article (read 2026-08-27)
DOT date code format before and after 2000, worked examples
Tire code - Wikipedia, revision read 27 August 2026 (read 2026-08-27)
Load range letters and ply ratings, M+S definition, sidewall marking glossary
Load Range - CJ Tire, undated reference chart (read 2026-08-27)
Load range letters A to N with ply rating equivalents
Tire Load Ranges: Complete Guide (B Through F) - TireGrades, updated 24 June 2026 (read 2026-08-27)
Load range letters B to F with ply ratings and maximum inflation pressures
Tire Load Rating Chart - Your Auto Vision, page dated 21 April 2026 (read 2026-08-27)
Load range letters B to G with ply ratings and maximum inflation pressures
What the 3PMSF Symbol Means for Winter Driving Safety - Les Schwab, undated reference article (read 2026-08-27)
3PMSF meaning, the medium packed snow test, what the symbol does not cover
What Is the 3PMSF Symbol and How Does It Affect Your Tires - DuallyWheels, undated reference article (read 2026-08-27)
3PMSF test standard and the 110 percent traction index threshold, M+S comparison

These are independent publishers, not independent measurements. Each one reproduces a table originally set by a standards body, so agreement between them shows a value was transcribed correctly, not that the underlying table is right. Where a figure is safety relevant, check it against the tire manufacturer's own data before relying on it.

Left out on purpose

Maximum inflation pressure for load ranges A and G through N. Fewer than two of the sources consulted published a figure. Of the charts that do publish one for G, the source consulted here gives 105 psi while other charts in circulation give 110 psi, so nothing is published for it.
DOT plant code lookup. Plant codes are assigned and revised by the federal regulator and the published lists in circulation are incomplete and out of date; a partial list here would be worse than none.
The DOT size code and type code are manufacturer-assigned and not standardised, so they cannot be decoded from a table at all.