just riding isn't hard isn't gong to get you towards your max.... if you want to test it then on a day when you are well rested and motivated to do it start with 10 minutes of warming up. Next try starting in a gear and pedaling with a high cadence. Shift to a harder gear one at a time while keeping up the cadence. Once it starts to become too hard for you to continue then sprint as hard as you can for 30 seconds and that should get you close to your max.