RUST PROOFING: There are two types of rust proofing that can be applied to the interior surfaces of the frames tubing. First there is the traditional paraffin based coating which coats the interior surface of the tube with a waxy substance that seals the metal from exposure to oxygen and moisture. This material is applied through holes drilled in the frame members at strategic locations and then sprayed in to the openings to coat the interior surfaces. All the holes drilled are then closed with plastic plugs that are then part of the frame and can be painted over to seal the mating line.

The second choice is relatively new to the market and that is the application of expanding foam to all the interior areas of the frame. This foam is water proof and sticks like glue to all surfaces. The application is once again through holes drilled in the tubing. The expanding foam is forced into one end of the tube length and allowed to ooze out of the other end to assure a complete fill. Once dry the over fill is cut away and the holes are filled with plastic plugs.
This foam application does two things to the structure. First it makes for an impenetrable water seal and secondly sound dampens the frame. You may think this a minor point but in fact the frame does resonates and amplify the vibrations caused by road conditions and those passed along by the drive train. Foam filling quiets the ride appreciably.

Both methods of rust proofing assure a rust free interior surface for the life of the frame