What is the 3% guideline for replacement tires?

The 3% guideline for replacement tires serves an important function in maintaining vehicle safety, performance, and overall handling characteristics. When replacing tires, ensuring that the diameter of the replacement tire is within 3% of the original tire diameter helps to keep the vehicle's speedometer accuracy, traction control systems, and anti-lock braking systems functioning properly. This range allows for a balance between adequate tire size for the intended application while minimizing potential issues such as uneven wear or changes in handling dynamics.

If the replacement tires are significantly larger or smaller than the original specifications, it can lead to complications such as altered speedometer readings, which might result in driver confusion regarding speed. Additionally, drastically different tire sizes could affect the vehicle's stability, increase the risk of mechanical failure, or impact the effectiveness of safety systems designed to respond to specific tire sizes.

Therefore, adhering to the 3% guideline is essential to ensure that the vehicle continues to operate safely and effectively after tire replacement.