You can increase the tyre size of the TVS Raider 125, but it is crucial to do so within a specific margin to maintain performance, handling, and safety. The stock tyre sizes for the TVS Raider 125 are 80/100-17 for the front and 100/90-17 for the rear. For an upgrade, it is advisable to stay within a 3% margin of the original tyre size. For example, upgrading to a 110/80-17 rear tyre, as seen in some reviews, can improve stability and cornering confidence without significant issues. However, it is important to ensure that the new tyre size does not compromise the integrity of the rims or affect the bike's overall geometry. Always check the space between swingarms and sprockets and keep the sidewall height as similar as possible to the original tyres to avoid any potential safety and handling issues[5).