When you get your car kit, take a look at the axles and wheels. A lot of kits have burrs and mold marks poking off the wheels and axles. Every one of those will slow your car down. Friction is enemy number one to your car. Smooth axles and wheels have less friction.
You can use a file to trim the mold marks off the axles. Then you can use some fine-grit sandpaper to take the rest of the mold marks off the axles and the wheels. Finally use some polishing compound from the auto supply store to polish up both the axles and the wheels.
The easiest way to sand or polish the axle is to put it in an electic drill and let the drill spin the axle at a low speed while you polish it. Kids, get your parent’s help with power tools.
There’s three places on the wheel that need polishing. Even rules that don’t allow you to modify the wheels will usually allow you to sand off and polish the mold marks. The wheel treads, where the wheel makes contact with the track is the first one. You need to sand off the mold marks. The easiest way to do this is to buy a mandrel at a hobby shop. A mandrel is a little tool that lets you attach your wheel to the end of an electric drill. You also need to sand off any mold marks on the inside and outside hubs of the wheel where they’ll make contact with the axle and the car body. And you’ll want to polish the inside of the wheel, where the axle runs through. The easiest way to do that is to put polishing compound on a pipe cleaner or a bit of cloth and run it through the wheel hole. Give the wheel a few light spins and then wash it out.