Your tire sidewall is a spec sheet. A string like 225/55R19 99V tells you the width, profile, construction, rim size, load rating, and top speed — and a separate DOT code tells you the week it was built. Here is how to decode all of it.
- 225/55R19 = width 225 mm / aspect 55% / Radial / 19-inch rim.
- The number after the size (e.g. 99) is the load index; the letter (V) is the speed rating.
- The last four digits of the DOT code are the week and year it was made.
- Match the size and ratings on your door jamb, not just whatever is on the tire now.
The size string
Take 225/55R19. The 225 is the section width in millimetres. The 55 is the aspect ratio — the sidewall height as a percentage of width. The R means radial construction. The 19 is the wheel diameter in inches.
A P in front (P225...) means passenger; LT means light truck, which carries a heavier load rating for trucks and towing.
Load index and speed rating
Right after the size you will see something like 99V. The 99 is the load index (a coded weight capacity), and the V is the speed rating. Your vehicle has minimum values for both — meet or exceed them. Fitting a lower load or speed rating than specified is unsafe.
The DOT date code
Near the rim you will find DOT followed by a string ending in four digits. Those four digits are the build date: week and year. '0125' is the first week of 2025. Tires age out at roughly 6 to 10 years even with good tread, so the date matters — especially when buying used.
Where do I find my correct tire size?
On the sticker inside the driver's door jamb, and in your owner's manual. That is the manufacturer's spec. The size on your current tires should match it — but if a previous owner fitted a different size, trust the door jamb.
How old is my tire?
Find the DOT code on the sidewall; the last four digits are the build date. '2224' means the 22nd week of 2024. Most tires should be replaced by 6 to 10 years of age regardless of tread, because the rubber hardens over time.
What does the load index and speed rating mean?
The load index is a code for how much weight the tire can carry; the speed rating letter is its tested top speed. Always meet or exceed your vehicle's specified ratings — going lower compromises safety.
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