Take away the sidewall and allow yourself to fully sharpen your edges. After you have sharpened your edges a few times the sidewall interferes with your tuning. It is essential to trim the sidewall so that you can accurately sharpen the edges. Too much sidewall prevents you sharpening your edges precisely. This is the most common reason for being unable to make a  consistently sharp edge. An easy to use tool. Product Code: EAACY4BL0046 Datawax Skiman Sidewall Remover | Ski Maintenance UK