i'm fairly new to the sport and I just picked up a hellfire truggy a couple days ago. Its a used one and I noticed someting odd. As I reach a decent speed and slam on the brakes, it makes a loud "rrRrRrrRrrtTtTT" sound. I looked at my bell n my spur and it seems to be wearing down a bit. Is that the problem? or is it normal? what should i do? thanks