How to read your tire door placard
Every line of the Tire and Loading Information label: original size, cold PSI front, rear and spare, seating and load limits, and what to do if it is missing.
Read the guide →Tire guides
Plain English guides for US drivers, grouped by task, with public NHTSA, USTMA and eCFR citations on each page.
Last updated: October 20, 2026
Short answer: start with your vehicle’s door placard. It lists the original tire size and the cold pressures the vehicle maker recommends, and most other tire questions (pressure, TPMS lights, replacement size, load index) build on it. The guides below are grouped by the job you are doing, and the table maps common questions to the page that answers them.
Jump to: Pressure, placard and TPMS · Tread, age and replacement · Ratings and sidewall specs · Seasons and storage · Find a guide by question · Simple tire check routine
Pressure, placard and TPMS
Tire placard checklist
What to copy from the door label before you shop, so a quote or a store visit starts from the right size and specs.
Read the guide →Recommended cold tire pressure (PSI)
Why the placard PSI, not the sidewall maximum, is the usual target, what cold means, why spare PSI can differ, and how much pressure drops in cold weather, with a PSI drop calculator.
Read the guide →TPMS warning light explained
Solid versus flash then solid lights, cold weather pressure drops, spare tire caveats, and why monthly gauge checks still matter.
Read the guide →Tread, age and replacement
Tire rotation patterns
How often to rotate (about 5,000 to 8,000 miles) and the pattern for FWD, RWD, AWD and 4WD, with diagrams and directional and staggered rules.
Read the guide →How to check tire tread depth
Wear bars, tread depth gauges, the limits of coin tests, and when to have a licensed installer look.
Read the guide →DOT date codes and tire age
How to read the four digit week and year code on the sidewall and why age matters alongside tread.
Read the guide →DOT date code decoder
Enter the last four digits of the DOT code to see the week and year a tire was made and its age today.
Read the guide →When to replace your tires
Tread, irregular wear, damage, age, and seasonal sets as replacement signals, with soft caveats.
Read the guide →Can you mix tires? Replace 2 or 4
USTMA and tire maker rules for replacing two vs four, putting new tires on the rear, mixing brands, and AWD diameter matching.
Read the guide →How long do tires last?
Typical miles (about 40,000 to 70,000 for all season tires) and years, 6 and 10 year age limits from Goodyear, Michelin and Continental, and a quick estimator.
Read the guide →Tire plug vs patch
Why a plug alone or patch alone is not a proper repair, USTMA and TIA limits (tread area only, 1/4 inch max), string plugs, sealant kits, and a repairable checker.
Read the guide →Tire sidewall bulge
Why a sidewall bubble means internal damage and replacement, how to tell it from a harmless radial indentation, what to do now, warranty facts, and a quick bulge or dent checker.
Read the guide →Plus sizing tires
Can you put bigger tires or wheels on your car? The six tire maker rules, the 3 percent diameter guideline, Extra Load pressure changes, AWD notes, and a plus size finder.
Read the guide →All weather vs all season tires
Why the 3PMSF snowflake symbol separates all weather from all season tires, a side by side table, Quebec and BC winter tire rules, one set or two, and a which tire fits my climate picker.
Read the guide →How long do winter tires last?
How many seasons and miles to expect, why to replace winter tires near 6/32 inch, age limits, a fall checklist, and how to make a set last longer.
Read the guide →Tire balancing vs wheel alignment
Vibration or pulling? Match your symptom to balancing, alignment or a brake check, with a quick in browser symptom checker and what to check first for free.
Read the guide →Nitrogen vs air in tires
Air is already 78 percent nitrogen. What a nitrogen fill really changes (a little slower pressure loss), cost, green valve caps, topping up with air, TPMS, and an air vs nitrogen pressure loss estimator.
Read the guide →Spare tire (donut) limits
Speed (usually 50 mph), distance, spare PSI, TPMS caveats, and when not to use a temporary spare, with OEM and NHTSA citations plus a miles remaining helper.
Read the guide →Ratings and sidewall specs
Load index and speed rating chart
How to read the service description, a chart of common passenger load indexes and speed symbols, and XL versus standard load notes.
Read the guide →UTQG tire grades explained
What treadwear, traction and temperature grades do and do not tell you, with NHTSA and eCFR citations.
Read the guide →How to choose the right tire size
A placard first process for size, load index, speed rating and climate category before you buy.
Read the guide →Tire size comparison calculator
Compare two sizes such as 225/65R17 and 235/60R18: diameter, sidewall, revs per mile, and speedometer difference.
Read the guide →Seasons and storage
Winter tires: when to switch and what to buy
Switch around 45°F (7°C), 3PMSF versus M+S, all season versus all weather versus winter, studded tire rules, tread for snow, and fitting four.
Read the guide →Seasonal tire storage
How to store an off season set: indoor versus outdoor, stacked versus upright, ozone and sunlight risks, and checks before reinstalling.
Read the guide →All-season vs winter vs summer tires
How the three categories differ by climate, with a quick comparison table.
Read the guide →All-season vs winter tires
When all-season tires may be enough, when winter tires are often considered, and 3PMSF versus M+S symbols.
Read the guide →Find a guide by question
| Your question | Where it is answered |
|---|---|
| What PSI should my tires be? | Cold tire pressure guide |
| How much does tire pressure drop in cold weather? | Cold weather PSI drop calculator |
| Where is the tire placard and what does each line mean? | Door placard guide |
| My tire pressure light is on. What does it mean? | TPMS warning light guide |
| Is my tread too low? | Tread depth guide |
| How old are my tires? | DOT date code guide |
| What does my 4 digit DOT code mean? | DOT date code decoder |
| Do I need new tires yet? | When to replace guide |
| Can I mix tire brands or replace only two? | Mixing tires guide |
| How long do tires last? | Tire life guide |
| Should I plug or patch a tire puncture? | Tire plug vs patch guide |
| Is a bulge or bubble on my tire sidewall safe? | Sidewall bulge guide |
| Can I put bigger tires on my car? | Plus sizing guide |
| Is nitrogen in tires worth it? | Nitrogen vs air guide |
| How fast and far can I drive on a donut spare? | Spare tire limits guide |
| How often should I rotate my tires? | Tire rotation guide |
| What do 94V or 91H mean on the sidewall? | Load index and speed rating chart |
| What does a 500 AA A UTQG grade mean? | UTQG guide |
| What size tire fits my car? | Tire size guide |
| Will a different tire size change my speedometer? | Tire size calculator |
| When should I put winter tires on? | Winter tires guide |
| How should I store my winter or summer set? | Seasonal storage guide |
A simple tire check routine
A general habit many drivers use, based on NHTSA consumer guidance to check pressure monthly with a gauge. Your owner’s manual and installer take priority.
| When | What to check | Guide |
|---|---|---|
| Monthly | Check cold pressure on all four tires and the spare with a gauge, against the door placard, not the sidewall maximum. | Pressure guide |
| Monthly | Look at tread across the full width of each tire. Wear bars or uneven wear are a reason to look closer. | Tread depth guide |
| When a light comes on | Note whether the TPMS light is solid or flashes then stays on, then check pressures with a gauge. | TPMS guide |
| Before buying tires | Copy the placard size and pressures, then match load index and speed rating at or above OEM. | Placard checklist |
| At each seasonal swap | Read the DOT date code, inspect for damage, and store the off season set clean, cool and out of sunlight. | Storage guide |