Yes, you can physically mount different size tires on a car, but it is generally not recommended and often unsafe without proper adjustments. Doing so can negatively impact vehicle handling, stability, and electronic systems like ABS and traction control. The key issue is maintaining a consistent rolling circumference—the distance a tire travels in one revolution—across all wheels to ensure accurate speedometer readings and even wear. For example, if one tire has a larger diameter, it rotates slower than others, potentially causing differential damage in all-wheel-drive vehicles. Always consult your owner's manual or a professional before making changes.
Installing mismatched tires can lead to several problems. The speedometer and odometer may become inaccurate because they are calibrated based on tire size. A larger tire will cause the speedometer to read slower than your actual speed, while a smaller tire makes it read faster. This can result in speeding tickets or incorrect maintenance intervals. Additionally, modern vehicles rely on wheel speed sensors for systems like anti-lock brakes (ABS) and electronic stability control (ESC). Inconsistent tire sizes can confuse these systems, reducing their effectiveness and increasing braking distances.
There are exceptions, such as when upgrading all four tires uniformly for better performance or off-road use. In these cases, ensure the new overall diameter is within 3% of the original to minimize issues. For all-wheel-drive (AWD) cars, manufacturers like Subaru and Audi specify that all tires must be within 2/32 of an inch in tread depth to prevent drivetrain stress. Always have a professional perform a wheel alignment after changing tire sizes to avoid premature wear.
Below is a table illustrating common tire size changes and their typical effects on speedometer accuracy, based on industry data from sources like the Tire and Rim Association. The data assumes an original tire size of 205/55R16, which has a rolling diameter of approximately 24.9 inches.
| Original Tire Size | New Tire Size | Diameter Change (inches) | Speedometer Error (%) | Potential Issue |
|---|
| 205/55R16 | 215/55R16 | +0.3 | +1.2 | Slight under-read |
| 205/55R16 | 195/65R16 | +0.4 | +1.6 | Increased rolling resistance |
| 205/55R16 | 225/50R16 | -0.2 | -0.8 | Over-read risk |
| 205/55R16 | 205/60R16 | +0.6 | +2.4 | ABS malfunction possible |
| 205/55R16 | 185/65R16 | +0.5 | +2.0 | Traction control issues |
| 205/55R16 | 215/50R17 | +0.1 | +0.4 | Minimal effect |
| 205/55R16 | 235/45R17 | -0.3 | -1.2 | Handling compromise |
| 205/55R16 | 195/60R16 | +0.2 | +0.8 | Fuel efficiency drop |
| 205/55R16 | 225/55R16 | +0.7 | +2.8 | Drivetrain wear in AWD |
| 205/55R16 | 205/50R17 | -0.4 | -1.6 | Braking performance loss |
If you must change sizes, stick to manufacturer-approved alternatives and consider recalibrating speed sensors. For safety, prioritize matching tires on the same axle at minimum.
