I noticed early on with my T-4 there was an area 75% to the right of the wheel which had a 'rough patch'. I assumed early on that I did something wrong I did not understand, and I waited for it to erode as the wheel was trued over time. Instead, the rough patch always persisted. Recently I decided to get the TT-50 truing tool, in part to solve this issue. As I ran the cutter across the wheel, it was doing a good job but suddenly once it approached that area the whole machine started to pulse/groan and I realized what was happening. On a micro-scale, the wheel is not revolving flush around the center. There is a high point, where the surface of the wheel bobs up/down on a micro scale, and trying to push the cutter across it was forcing it to oscillate from the 0.01" cut, to who knows how deep? It's deep enough that I can feel it with my fingertip as I run it across the surface. I guess the 'rough patch' I always noticed was from my tools attempting to sharpen in this bobbing area. I have had my tormek for 8 months now but I know the problem has always been there, I just finally know why. Where do I go from here... thanks