This goes along with what Tim said. A few weeks ago at our local track one of the TaG guys showed up with a late model used TonyKart . Let me say first our local track is rough, real bad in spots. He went out for the first heat race, and about 6 laps in he spun around awkwardly for what appeared no reason at all. When he picked up the kart to bring it to the pits the frame had bent in a V at the waist, right where the chassis wear was located. He is a big guy, probably 6’3″ and 240 or so, in great shape. It appears the chassis was flexing under his weight and rubbing, and just bent under the strain compounded by the thinner tubing due to wear and the extreme flexing when hitting the bumps. But to be fair, it probably could happen to any kart that flexes a lot. I watched an Ikart race a couple weeks back and its unbelievable how much they flex and twist. I can’t believe they would last long if they were experiencing flat spotting.