I have an old Kurt kinetic fluid trainer. Basically the knob eventually stripped (just this morning in fact). I had to hacksaw the plastic knob off to get to the nut that was stuck on the bolt that it was attached to. In the process i dinged the roller the tire rides on. So, how do I get those grooves my hacksaw put into that metal out? What grit of paper should I use? Or, do I not need to do that at all? My concern is over time it will eat up my trainer tire.