My goal has been to enter the proxy races and have been working to improve my cars. I recently built two cars that ran sub 3.0.(2.997, 2,994). I found the cars held that speed for about 2-3 weeks then times began to fall off. When I re-prepped the wheels and axels, I was never able to get the time back under 3.0. 3.015 seems to be the new norm. I noticed that the DFW had worn a groove in the body. Is the a way to prevent this when bushing and spacers are not allowed? Or is it just typical for cars to become slower with use?