Polini +10% toruq spring for Yamaha T-Max 500, 500i and 530i models as listed, ideal for lightly tuned engines. The springs press the gear on the rear converter onto the belt, iIt also creates pressure to shift the variator. A lighter pressure is required once a motor has been tuned to prevent the engine from moving into a dangerously high rev range. The pressure of the springs is closely tied to the variator. If a spring is fitted, it must be matched to the variator. Original spring weight: 65/70mm/kg. Polini spring weight: 65/80mm/kg. Spring thickness: 6mm. Total length: 128mm. Internal diameter: 58mm. Number of coils: 6. Suitable for the follow Yamaha T-Max models: T-Max 500 01-03 SJ01 T-Max 500i 04-06 SJ031 T-Max 500i 07 SJ051 T-Max 500i 08-11 SJ061 T-Max 500i ABS 05-06 SJ034 T-Max 500i ABS 07 SJ052 T-Max 500i ABS 08-11 SJ064 T-Max 500i Black Max 06 SJ031 T-Max 500i Black Max 07 SJ051 T-Max 500i White Max 10- SJ06 T-Max 530i 12-14 SJ091