The Yamaha FZS V3 typically comes with a stock tire size of 100/80-17 for the front and 140/60-17 for the rear. While it's technically possible to fit a 140/70-17 tire on the rear wheel, it is not recommended without considering certain factors.
Wheel Clearance: The FZS V3 has limited clearance in the rear wheel area. The larger tire size may result in the tire rubbing against the swingarm or other components, potentially causing damage or affecting the bike's handling.
Speedometer Accuracy: Changing the tire size can affect the accuracy of the speedometer reading. A larger tire diameter can result in an overestimation of your actual speed.
Handling and Stability: Altering the tire size may impact the bike's handling characteristics. A wider tire could affect the bike's agility, cornering ability, and stability, especially if it exceeds the recommended specifications.
It's generally advisable to stick to the manufacturer's recommended tire sizes or consult with a trusted Yamaha dealer or professional motorcycle technician for advice specific to your bike model. They can provide guidance based on your intended use and the potential implications of installing a different tire size.