To find the right tire size for my car, start with the tire-information label fitted to the vehicle, then confirm the recommendation in the owner’s manual. The size printed on the tires already installed is useful to compare, but it may not be correct—especially if the car has changed hands or its wheels have been replaced. Check the specified size for your exact model and trim, including any different front and rear sizes. Before buying, also confirm the load and speed ratings, wheel fitment, and any requirements for your vehicle’s drivetrain. The correct size is the one approved for the car, not simply one that can be mounted on its wheels.
Look first for the vehicle’s tire-information placard, commonly found on the driver’s door jamb or door opening. It lists the recommended tire size and the vehicle’s cold tire-pressure setting. The owner’s manual is another reliable place to check; it may explain which sizes apply to different trims or wheel packages. If the car has more than one approved fitment, make sure you identify the one that matches your vehicle.
The tire sidewall shows the size of the tire currently fitted, but treat it as a cross-check rather than your final authority. A previous owner may have chosen a different size, or a tire shop may have fitted a non-standard replacement. If the placard is missing or unclear, use the manual or ask a tire professional or vehicle dealer to confirm the specification using the car’s year, make, model, trim and, when needed, vehicle identification number (VIN).
| Where to check | What it can tell you | What to watch for |
|---|---|---|
| Vehicle tire-information placard | Recommended tire size and cold inflation pressure | Confirm it belongs to the vehicle and check for separate front and rear sizes. |
| Owner’s manual | Approved sizes, fitment notes and instructions for checking pressure | Some manuals cover multiple trims; match the information to your car. |
| Current tire sidewall | The size and service description of the tire fitted now | It does not prove that the tire is the manufacturer’s recommended fitment. |
| Dealer or tire professional | Help confirming fitment when labels or records are unavailable | Give the exact vehicle details and mention any non-standard wheels or modifications. |
If you find different sizes listed for the front and rear, don’t assume the difference is an error. Some vehicles use a staggered setup, with wider or otherwise different tires at one end. Replacing those tires with one matching size all around can change the car’s intended fitment. Check the placard and manual before ordering, and make sure the replacement plan accounts for both axles.
A tire marking such as P225/65R17 102H combines several specifications. The example below is for explaining the format only; it is not a recommendation for any particular car. Read the whole marking, not just the first set of numbers.
| Marking | Meaning | Why it matters |
|---|---|---|
| P | Indicates a P-metric passenger tire designation. | Other tires may use different designations, such as LT for light truck. Use the type specified for the vehicle. |
| 225 | Nominal section width in millimetres. | It describes the tire’s width, not the width of the wheel. |
| 65 | Aspect ratio: the sidewall height as a percentage of the tire’s width. | A lower or higher ratio changes the tire’s profile and can affect fitment and ride characteristics. |
| R | Radial construction. | This is a construction type, not a measurement of the tire’s radius. |
| 17 | Wheel diameter in inches. | The tire must fit a wheel with the specified diameter. |
| 102H | Load index and speed rating. | These ratings are part of fitment and should meet the vehicle’s requirements. |
In this example, 225 is the tire’s nominal width, and 65 describes the sidewall height in relation to that width. The 17 refers to the diameter of the wheel the tire is designed to fit. A tire with the same wheel diameter but a different width or aspect ratio is not automatically an acceptable substitute.
The number and letter after the size are also important. The load index identifies a tire’s rated load capacity under specified conditions, while the speed rating indicates a tested speed category. Don’t assume that a tire with the right size numbers is suitable if its service description does not meet the car’s requirements. Check the manual, placard or vehicle-specific fitment information, particularly if you’re considering a different tire type.
Online selectors can narrow down options, but the result depends on the vehicle details entered and the accuracy of the fitment data. If several sizes appear, don’t choose based on price, appearance or wheel diameter alone. Compare the selector’s result with the placard and manual, and get clarification if they disagree.
A tire that is too wide, too tall or otherwise unsuitable can interfere with surrounding parts, including the wheel well or suspension. A change in overall tire diameter can also affect the relationship between wheel rotation and distance travelled, which may influence speedometer readings and the operation of vehicle systems. The exact effect depends on the vehicle and the size change, so don’t rely on appearance or a general “close enough” rule.
Fitment can also influence how the car responds to steering inputs and how the tire carries the vehicle’s load. Braking and handling depend on more than size: tire condition, tread, pressure, road conditions and driving all matter. Still, choosing the specified fitment helps avoid introducing an unnecessary variable when you replace tires.
Drivetrain matters too. Vehicles with all-wheel drive can have requirements about tire size and the difference in rolling circumference between tires. Replacing only one tire, or combining tires with substantially different wear, may not suit every vehicle. Check the manual for replacement guidance and ask a tire professional before mixing sizes or tread depths. If the car has a staggered setup, follow the specified front and rear arrangement rather than assuming all four tires should match.
Sometimes a vehicle has more than one approved size, often because different trims or factory wheel options use different fitments. Those alternatives are not interchangeable by default. Confirm that the alternative is listed for your exact vehicle or has been verified by a qualified professional who can account for the wheel dimensions, clearances, load requirements and drivetrain.
Changing to a different wheel diameter or tire profile may be part of a planned wheel-and-tire package, but changing only one part of the setup can create problems. The tire must suit the wheel’s diameter and width, and the complete assembly must clear the vehicle under normal use. A retailer’s general fitment tool is not a substitute for confirming a non-standard setup against the car.
Be especially cautious if you’re considering a larger wheel with a lower-profile tire, or a tire that is wider than the specified one. The setup may alter ride feel and steering response, and there may be less clearance than expected. Ask the shop to explain how it verified the proposed fitment and whether the vehicle maker lists it as an approved option. If the answer is uncertain, stick with a size shown on the placard or in the manual.
Keep the pressure information separate from the size information when you shop. The placard gives the vehicle’s recommended cold inflation pressure; the tire sidewall provides tire-specific markings and a maximum-pressure limit. Follow the vehicle’s pressure guidance for normal use, and consult the manual for adjustments when carrying heavier loads or other special situations.
A dealer or tire retailer may be able to use the VIN to identify vehicle details and help confirm the original fitment. The VIN is useful when trim information is unclear, but it doesn’t replace checking whether the wheels or tires have been changed since the car was built.
Many vehicles use the same size on all four wheels, but some have different front and rear specifications. Follow the placard and manual rather than assuming a uniform set is correct. This is particularly important when replacing only two tires.
No. It tells you what is fitted, not whether it matches the car’s approved specification. Compare it with the placard or manual, especially if you bought the vehicle used or know that its wheels have been replaced.
Don’t choose a lower rating just because the size matches. The replacement should meet the vehicle’s stated requirements, and any proposed change should be checked for that specific vehicle and tire type.
Pressure recommendations are tied to the vehicle and its approved setup, not simply copied from the tire’s maximum-pressure marking. If you change to a non-standard size, have a qualified tire professional confirm the appropriate fitment and pressure guidance rather than guessing.
Pause before ordering. Check the owner’s manual and determine whether the current tires are an approved alternative or a previous non-standard replacement. If the information still conflicts, ask a dealer or qualified tire professional to verify the correct setup using the vehicle details and wheel specifications.
For the right tire size for my car, use the vehicle placard and owner’s manual as your starting point, then confirm the full size and ratings for each axle. Treat the tires currently fitted as evidence to check, not as proof. If the car has different wheels, modifications or conflicting fitment information, get the complete setup verified before buying.
