What size tires should I put on?
The safest starting point is the OEM size recommended by your vehicle’s manufacturer. In most cases, you should stick to that size, and any deviation should be considered carefully for clearance, load capacity, speed rating, and potential speedometer effects.
In this guide, we’ll explain how to locate the correct size, how to read tire markings, what trade-offs come with changing size, and practical tips for choosing tires that fit your climate and driving style. The goal is to help you make an informed choice that preserves safety and performance.
Start with the OEM specification
Manufacturers publish a recommended tire size for each model, usually on a placard in the driver’s door jamb and in the owner’s manual. The notation you’ll see on tires and in manuals—such as P205/65R16—contains key details about width, profile, construction, and wheel diameter. Keeping to the OEM size is the simplest way to maintain the vehicle’s designed handling, ride, and safety systems.
Below is a practical route to determine if you can or should deviate from the original size. It includes steps you can follow before purchasing new tires.
To help you determine the right size and whether you can safely change it, consider these steps:
- Find the OEM tire size on the door jamb placard, in the owner’s manual, or on the current tire sidewall; this is your baseline, especially if you plan to replace with the same type.
- Learn the meaning of the size notation (width x aspect ratio x construction x wheel diameter), e.g., 205/55R16 translates to 205 mm wide, 55% of width as the sidewall height, 16-inch wheel, radial construction.
- Check the load index and speed rating printed on the tire sidewall and ensure they meet or exceed the vehicle’s requirements as listed in the manual or placard.
- Assess clearance and fitment: wider tires, different profiles, or larger wheels can rub fenders, suspension components, or brakes; measure or consult a professional to confirm there’s no interference.
- Decide whether you need a tire type based on climate and driving needs (all-season, winter, summer/performance, or off-road).
- Consider overall diameter change: large jumps in width or diameter can affect speedometer accuracy and traction control; aim for a diameter change within a few percent of the OE size if possible.
Following these steps helps ensure you choose a size that preserves safety, accuracy, and driving feel while meeting your practical needs.
Decoding tire labels and what they mean
Width, aspect ratio, and diameter
The first three numbers in a size like 205/55R16 describe width in millimeters, the aspect ratio (the height of the sidewall as a percentage of width), and the wheel diameter in inches. Wider tires can improve grip in some conditions but may affect fuel economy and clearance, while a shorter sidewall tends to sharpen handling but reduce ride comfort.
Construction and load/speed ratings
The "R" indicates radial construction. The load index and speed rating (e.g., 91V) tell you how much weight the tire can carry and the maximum safe speed. Use a tire with a load index and speed rating equal to or higher than your OE specification to maintain safety and performance.
Safety considerations when changing size
Impact on vehicle systems
Altering tire size can influence speedometer accuracy, ABS and traction control calibration, and overall handling. A diameter that is too far from the OEM can cause these systems to behave unpredictably or become less effective.
Clearance and compatibility
Wider tires or different wheel diameters can rub the fenders, suspension components, or brake calipers. Always verify that the new setup fits within the wheel wells and does not interfere with movement or steering.
When you can deviate from OEM size
Reasonable and safe deviations
If you have a compelling reason (e.g., winter tires in a colder climate, better off-road capability, or availability issues), you can choose a size that remains close to OE diameter and preserves the vehicle’s design intent. In many cases, dealers and tire professionals can recommend a size within a 2–3% diameter difference to minimize risk.
Tire replacement scenarios: two tires vs. all four
Practical guidance
For safety and handling consistency, replacing all four tires is often best, especially if tread depth is uneven or wear is significant. If you replace fewer than four, install the new tires on the axle with the least tread and ensure the overall diameter difference between the new and existing tires is minimized. Always consult your vehicle’s manual or a tire professional for model-specific guidance, as some cars require a particular arrangement to preserve stability control and traction performance.
Practical tips for shopping
Shop with your vehicle’s requirements in mind. Look for tires that meet or exceed the OEM load index and speed rating, maintain a similar overall diameter to OEM, and suit your climate and driving style. When in doubt, seek input from a qualified tire technician or your dealership to ensure the chosen size provides reliable handling, braking, and comfort.
Summary
The best approach to tire sizing is to start with the vehicle manufacturer’s recommended size and only consider deviations after evaluating clearance, load and speed ratings, and the impact on speedometer/vehicle systems. Use the OEM size as your baseline, understand tire markings, and weigh your needs for climate, performance, and budget. Replacing all four tires is often the safest option when changing size, but if you replace only two, place them on the axle that affects stability the most and keep overall diameter differences minimal. With careful verification and, if needed, professional guidance, you can choose tire sizes that keep your vehicle safe, predictable, and performing as intended.
Conclusion: Accurate tire sizing is essential for safety and performance. Start with the OEM specification, verify all ratings, assess clearance, and consider your climate and driving style before making a change. When in doubt, consult a tire professional to ensure optimal fit and reliability.
