PJ. I have just checked the blades speed and the machine is running at 17,740FPM when the motor is at 3600 RPMs. The spindles are running at 3800 rpms and should be running at 3980 rpms. The tension is correct and the belts and pulleys look good. Please check with the factory and let me know ASAP what they say the spindle speed should be at the advertised 18,600 Blade tip. I have a industrial optical tachometer. It was calibrated before and after using it on the mower. It was within 1 rpm @ 7200. The machine is back at the dealer right now.