Quick Answer: Tire Specs at a Glance
- Tire size code (e.g., 225/65R17): width in mm (225), aspect ratio/sidewall height as a percentage of width (65), radial construction (R), and rim diameter in inches (17).
- Load index (e.g., 102): a number that maps to the maximum weight, in pounds, one tire can safely carry.
- Speed rating (e.g., H): a letter showing the top sustained speed the tire is built to handle; must match or exceed your vehicle's factory rating.
- Tread depth: measured in 32nds of an inch; 2/32" is the legal minimum in most states, but real-world stopping performance starts degrading well before that.
- UTQG rating: a treadwear/traction/temperature grade stamped on the sidewall, useful for comparing tires within the same brand, not across brands.
- Tire age (DOT date code): a 4-digit code (e.g., "2324" = 23rd week of 2024) showing when the tire was made; most manufacturers recommend replacement by 6-10 years regardless of tread left.
- All-season vs. summer vs. winter: The type you select comes down to a compound and tread-pattern tradeoff between performance for particular conditions (snow, wet, dry) and year-round convenience.
This guide breaks down what each of those specs actually means, why it matters, and includes real numbers to put them in context.
1. The Tire Size Code
The tire size code is found on the sidewall, for example 225/65R17 102H. Each part means something specific:
- 225: the tire's width in millimeters, measured sidewall to sidewall.
- 65: the aspect ratio: the sidewall's height as a percentage of the width. In this case, the sidewall is 65% as tall as the tire is wide.
- R: radial construction, which is how virtually every passenger tire sold today is built.
- 17: the wheel diameter, in inches, that the tire is designed to fit.
- 102: the load index (more below)
- H: the speed rating (more below)
2. Load Index Number
The load index is a number that corresponds to a standardized chart showing the maximum weight, in pounds, that one tire can safely carry when properly inflated. A tire marked "102," for example, is rated to carry 1,819 lbs per tire — but you look that up on a chart rather than reading it directly off the sidewall.
This matters because a lower load index than your vehicle's factory spec isn't a cosmetic downgrade — it's a real capacity shortfall, especially on SUVs, trucks, or anything that carries passengers, cargo, or (for EVs) the extra weight of a battery pack. Installing a tire with a higher load index than stock is fine; going lower is not.
3. Speed Rating (the letter that comes after the load index)
The speed rating is a letter (H, V, W, and so on) indicating the fastest sustained speed a tire is built to handle safely under its rated load. It's determined by lab testing. The tire runs against a large drum at increasing speed until it's held its rated speed for a set period without failing.
A few common ratings and what they mean:
- S — 112 mph
- T — 118 mph
- H — 130 mph
- V — 149 mph
- W — 168 mph
- Y — 186 mph
Although the code references speed, it’s not about how fast you drive but rather about the heat generated. The faster you drive, the more heat inside the tire. So the speed rating shows how the tire’s build manages the heat without failing. Winter tires can often have lower speed ratings, since those compounds are built for gripping ice and snow, rather than high-speed heat.
To know what rating your vehicle needs, look inside the door jamb for the sticker or at the owner’s manual.
4. Tread Depth
Tread depth is measured in 32nds of an inch because that's the height of the built-in tread wear indicator bars — small raised rubber strips molded into the grooves that become flush with the tread surface once a tire is worn down to 2/32". That's also why 2/32" became the legal minimum tread depth in most U.S. states: it's simply the point where a simple, visible physical marker appears, not because 2/32" was proven to be a safe stopping distance.
The real safety threshold is closer to 4/32", not 2/32". A study found that tires with less than 4/32" of tread may lose roughly 50% of available wet-road friction, even before hydroplaning starts to happen. (Commentary: Legal Minimum Tread Depth for Passenger Car Tires in the U.S.A.—A Survey)
NHTSA's own research found tire-related crash involvement climbs from about 2.4% at near-full tread depth to roughly 8% at 4/32" and up to 26% once tires are fully worn (0-2/32"). That's why most tire retailers recommend starting to shop for new tires at 4/32" rather than waiting until the tread wear bars actually show. (NHTSA report DOT HS 811 617, "Tire-Related Factors in the Pre-Crash Phase" (April 2012))
5. Tire Age (the spec most people never check)
A tire sidewall contains a lot of important information, including a 4 digit number for the tire age. For example, the number 2324 means the tire was made in the 23rd week of 2024. The first two digits will always correspond to the week of the year, and the last two numbers will be the year.
The age matters because rubber will degrade over time due to temperature cycles and UV exposure. It’s recommended that tires are replaced 6-10 years from the manufacture date, not the purchase date. So when you’re buying a “new” tire, check to see the tire age, as it could have been sitting in a warehouse.
6. All-Season vs. Summer vs. Winter (the tradeoff, not the marketing)
Different seasonal tires have different capabilities. It all depends on what weather conditions you live in and how much driving you do.
- All-season: great for handling a range of temperatures, as well as mild to moderate weather conditions. A middle of the road solution.
- Summer/performance: a stiffer, grippier compound optimized for dry and wet traction in warm temperatures, but the same compound gets hard and loses grip below roughly 45°F.
- Winter/snow: a much softer compound designed to stay flexible in freezing temperatures, with an aggressive tread pattern for snow and ice, at the cost of faster wear and a lower speed rating in warm weather.
Interesting Tire Stats (with sources)
- Only 19% of U.S. consumers properly inflate their tires, according to NHTSA's TireWise program. This means that roughly four out of five drivers are running on tires that are either over- or under-inflated. (NHTSA)
- Properly inflated tires can extend a tire's average life by 4,700 miles and save up to 11 cents per gallon in fuel. (NHTSA)
- In 2024, 511 people died in tire-related crashes in the U.S. (NHTSA)
- 336.3 million tires were shipped in the US in 2025. This is estimated to grow to 338.9 million units in 2026 (UStires.org)
- Vehicles with tires underinflated by more than 25% of the recommended pressure are three times more likely to be involved in a tire-related crash than vehicles with properly inflated tires, according to a NHTSA crash-data study covering 2005-2007. (NHTSA)
- TPMS saved an estimated $511 million across the U.S. vehicle fleet in 2011 through reduced fuel consumption from properly inflated tires, and saves a typical passenger car about 9.32 gallons of fuel over its first eight years and a typical LTV 27.89 gallons of fuel (NHTSA)
- Of rolled-over passenger cars, 15.7% were tire-related crash vehicles, which is the highest as compared to other body types: SUVs (9.4%), pickups (8.4%) and vans (8.1%) (NHTSA)
- NHTSA's April 2012 report "Tire-Related Factors in the Pre-Crash Phase" found tire-related issues contribute to approximately 200,000 accidents a year
- More than a quarter of cars and about a third of light trucks/SUVs on U.S. roads have at least one tire underinflated by 8 psi or more below the manufacturer-recommended level, according to a NHTSA-based U.S. Government Accountability Office report. (GAO Report for NHTSA)
- Tire-related crash involvement rises from about 2.4% at near-full tread depth to roughly 26% once tires are fully worn (0-2/32"), based on NHTSA crash data analysis. (NHTSA)
- Tires with less than 4/32" of tread may lose roughly 50% of available wet-road friction, even before hydroplaning occurs, according to a peer-reviewed traffic safety study. (Commentary: Legal Minimum Tread Depth for Passenger Car Tires in the U.S.A.—A Survey)
- 79% of end-of-life tires were consumed by recycling/reuse markets in the U.S. in 2024 — up 10.5% from the prior report. This outpaces recycling rates for metal, glass, aluminum, plastic, and paper, according to the U.S. Tire Manufacturers Association's 16th End-of-Life Tire Management Report. (UStires.org)
- The U.S. once had over 1 billion scrap tires stockpiled nationally; that number dropped by 94% through three decades of USTMA-led recycling efforts. (UStires.org)
- U.S. tire manufacturing has an annual economic footprint of $259.5 billion, responsible for more than 329,527 U.S. jobs in manufacturing, distribution, and retailing, plus another 606,477 jobs in supplier and induced activities — a total of over 936,000 jobs nationwide. (UStires.org)
- 61% of buyers replaced their tire sets when their current tires were worn. 17% bought new tire sets because they experienced problems like noise, vibration, tread separation. 14% bought when their tires had irregular wear. A flat tire led to 8% of purchases. (Consumer Reports)
- About 22% of surveyed CR members bought or installed tires at independently owned tire stores (including local mechanics); 15% used car dealerships; Discount Tire/Tire Rack led retail chains at 17%, followed by Costco at 16% (Consumer Reports)
- When buying new ties, 85% of buyers opted for all-season tires (Consumer Reports)
- When considering new tires, consumers appear to prioritize function over form. They felt the following factors were “very important” when buying tires, with wet grip the top concern followed by handling performance. (Consumer Reports)
- Wet Grip - 74%
- Handling - 73%
- Treadwear - 66%
- Ride comfort - 57%
- Noise - 48%
- Winter Grip - 47%
- Price - 38%
- Fuel efficiency/EV range - 35%
- Same brand - 23%
- Sustainable materials - 12%
- Appearance - 9%
