Reading a tire sidewall comes down to decoding one string, like P225/60R16 98H: the letter identifies tire type, the first number is width in millimeters, the number after the slash is the aspect ratio (sidewall height as a percentage of width), R stands for radial construction, the next number is wheel diameter in inches, and the final code is the load index and speed rating.
Here’s what every segment of that code actually means, plus how to find your tire’s manufacture date and safe replacement timeline.
Key Takeaways
- P225/60R16 98H breaks into six distinct pieces of information — type, width, aspect ratio, construction, diameter, and load/speed rating.
- The three-digit number is tire width in millimeters; the two-digit number after the slash is the sidewall height as a percentage of that width.
- The four-digit DOT code (like 2524) tells you the exact week and year the tire was manufactured.
- Your vehicle’s correct tire size and PSI are on the driver’s door jamb sticker, not necessarily what’s currently mounted on the car.
Breaking Down the Tire Size Code
A string like P225/60R16 98H looks cryptic at a glance, but each character carries a specific, standardized meaning that tells you nearly everything about the tire: type, width, profile, construction, wheel diameter, load index, and speed rating (AutoZone).
Tire Type: The Letter Prefix
A P prefix, as in P225/65R17, identifies a passenger tire built for cars, minivans, SUVs, and light-duty trucks used mainly to carry people. An LT prefix identifies a Light Truck tire with a stiffer carcass and higher load capacity, engineered for towing, heavy payloads, and applications that demand more structural strength (Michelin). Some tires have no letter prefix at all, which typically indicates a Euro-metric sizing standard used on many European vehicles.
Width, Aspect Ratio, and Construction
In P225/60R16, the 225 is the tire’s width in millimeters, measured from sidewall to sidewall. The number after the slash — 60 in this example — is the aspect ratio, meaning the sidewall height equals 60% of the tire’s width; a lower aspect ratio means a shorter, stiffer sidewall typical of sportier vehicles, while a higher number means a taller, more cushioned sidewall (Tire Rack). The R stands for radial construction, which is the industry standard for essentially all passenger and light truck tires manufactured today.
Wheel Diameter, Load Index, and Speed Rating
The number following the R — 16 in our example — is the wheel diameter in inches, telling you what size rim the tire is built to fit. After the size code, a separate number and letter combination like 98H indicates load index (the maximum weight the tire can safely carry) and speed rating (the maximum sustained speed the tire is engineered to handle) (Les Schwab).
| Speed Rating | Max Speed | Common On |
|---|---|---|
| S | 112 mph | Family sedans, minivans |
| T | 118 mph | Family sedans, crossovers |
| H | 130 mph | Most family sedans |
| V | 149 mph | Sport sedans, coupes |
| Z/W/Y | 149+ mph | Performance and sports cars |
Always match or exceed your vehicle manufacturer’s specified load index and speed rating when replacing tires — going below either spec can affect handling, load safety, and in some cases insurance liability. If you’re not sure your current tires match spec, our guide on how to put air in a tire also covers where to find your vehicle’s correct PSI, which is on the driver’s door jamb sticker rather than the tire sidewall itself.
Finding the Manufacture Date (DOT Code)
Every tire carries a DOT code ending in four digits that identify the week and year of manufacture — the first two digits are the week, and the last two are the year. For example, a code ending in 2524 means the tire was made in the 25th week of 2024 (BFGoodrich). This matters even for a tire with plenty of tread left, since rubber compounds degrade with age regardless of mileage, and most manufacturers recommend replacement by around 6-10 years from the manufacture date.
If you’re evaluating a used car and want to check tire age as part of a broader inspection, this DOT code is one of the fastest checks you can do — a tire with deep tread but a decade-old manufacture date is still a real safety concern.
Frequently Asked Questions
Can I mix different tire sizes on the same vehicle?
Generally not recommended for most vehicles — mismatched tire sizes can affect handling, all-wheel-drive systems, and ABS/traction control calibration. Some performance vehicles are designed with staggered fitments as an exception, but that’s specified by the manufacturer, not something to improvise.
Does a higher speed rating mean a better or safer tire overall?
Not necessarily better across the board — a higher speed rating typically comes with a stiffer, more performance-oriented compound, which can mean a firmer ride and sometimes shorter tread life compared to a touring-oriented tire with a lower rating.
What if my tire sidewall code doesn’t match my door jamb sticker?
That’s worth investigating — it could mean a previous owner installed a different size, which isn’t automatically dangerous but should be checked against your specific vehicle’s approved tire size range before you assume everything’s fine.
How do I know if a tire is too old even if the tread looks fine?
Check the DOT date code — if it’s beyond roughly 6-10 years old regardless of remaining tread depth, most manufacturers and tire safety organizations recommend replacement due to rubber compound degradation.
The Bottom Line
A tire sidewall code like P225/60R16 98H packs in tire type, width, aspect ratio, construction, wheel diameter, and load/speed rating — all standardized so you can decode any tire at a glance. Pair that with checking the DOT manufacture date, and you have everything you need to confirm a tire is the right size and still safe to use, whether you’re buying replacements or inspecting a used car.
Need help matching the right tires to your vehicle or assessing tire-related damage? Contact San Diego Bumper and Collision for guidance.
