Buying tires starts with the door-jamb placard, not the tire currently on the car — that placard lists the size and ratings your vehicle actually requires.
Without the right numbers, you’re choosing between whatever a salesperson has in stock. Three minutes reading the Tire and Loading Information Label on the driver’s side door edge hands you the size, load index, and speed rating your vehicle was built around. Find the spec, decode it, check the date on the rubber, then find out what the quoted price covers.
Where The Correct Tire Size Actually Lives
The door-jamb placard is the authoritative source for tire size and recommended inflation pressure, and it outranks whatever is on your wheels now. A previous owner may have swapped on a different size, and used-car lots do it routinely. If the sidewall code and placard disagree, follow the placard. The owner’s manual lists the same spec, but the door sticker is faster to reach.
Factor in where you drive — snow, standing water, gravel, and highway miles push toward different tread designs and compounds. Size is a hard requirement; type is your choice.
Reading The Sidewall Code Before You Buy
Every tire carries a string like 205/55 R16 91V. Each block compares against your placard:
- 205 — section width in millimeters.
- 55 — aspect ratio: sidewall height as a percentage of width.
- R — radial construction.
- 16 — wheel diameter in inches.
- 91 — load index: maximum weight carried at maximum inflation pressure.
- V — speed rating: rated maximum speed.
Load index and speed rating are where budget shoppers get burned. A cheaper tire with a lower load index may fit the rim and still be wrong for the vehicle. Match or exceed the placard. The sidewall also holds a DOT/TIN code; its last four digits are the manufacturing week and year — the only reliable way to know how long a tire sat in a warehouse. Ask to see the actual tires being sold, not a floor display.
Condition Checks And Fitment Rules
Replace at 2/32 inch of remaining tread, or when you’re close to it. NHTSA guidance centers on correct size and vehicle-specific fitment, which is why a worn-but-oversized set is still the wrong set. Run your hands over each sidewall and look for cuts, bulges, or exposed cords — any means the tire is done, regardless of tread.
Two rules that surprise people: stay in the same tire category as what’s installed, and when replacing only two tires, put the new pair on the rear axle — that keeps the back of the car from breaking loose first in wet conditions.
| Check | What To Confirm | Why It Matters |
|---|---|---|
| Door placard | Required size, load index, speed rating | Overrides a mismatched tire already on the car |
| Sidewall code | Width, aspect ratio, rim diameter | Confirms physical fit before mounting |
| Load and speed rating | Numbers and letter after the rim size | Undersized ratings fail under load or heat |
| DOT date code | Last four digits: week and year | Reveals how old the rubber really is |
| Tread depth | 2/32 inch minimum | Wet grip disappears below this point |
| Sidewall condition | Cuts, bulges, exposed cords | Structural damage can’t be repaired |
| Quoted price contents | Mounting, balancing, disposal, TPMS, warranty | The cheap quote often isn’t the cheap total |
Once your size is locked in, comparing what tires deliver for the money gets easier — our breakdown of tested budget-friendly tire picks covers which sets hold up under real driving.
What The Quoted Price Should Include
A tire price means nothing until you know which services ride along. Mounting and balancing are the baseline. Confirm old-tire disposal, valve stem replacement, and a TPMS reset if your vehicle has sensors. Ask about the road hazard warranty and whether rotations are bundled in — a $20-per-tire difference flips fast once disposal and sensor service get itemized separately. Michelin’s tire size guide and Bridgestone’s how-to-buy walkthrough stress the same order: verify fitment first, compare second. Then confirm the DOT date on the exact set going onto your wheels and inspect them before mounting.
NHTSA’s tire safety page is the reference to keep handy. NHTSA’s tire safety guidance lays out the same 2/32-inch threshold and inspection points used above.
FAQs
Can I use a different size than the door sticker lists?
The placard is the spec your vehicle was engineered around, so a different size can throw off speedometer readings and clearance. If the tires on the car now don’t match, that usually means a previous owner changed them, not that the sticker is outdated. Use the placard.
How old is too old for a new set of tires?
Check the DOT code’s last four digits for the manufacturing week and year. There’s no single expiration rule, but rubber ages even in storage. If a “new” tire shows a date several years back, ask why before buying, and inspect it for cracking.
Does the cheapest quote usually include installation?
Often it doesn’t. Mounting, balancing, valve stems, TPMS resets, and disposal frequently get added on top. Ask for the out-the-door total before comparing two shops, because the lower sticker price can cost more once those line items appear.
References & Sources
- National Highway Traffic Safety Administration. “Tires” Source for the 2/32-inch tread threshold, sidewall inspection points, and replacement guidance.
- Michelin. “Find Your Tire Size” Supports placard-first size verification and sidewall code reading.
- Bridgestone. “How to Buy Tires” Source for the buying sequence and price-inclusion checks.