How to Bondo Lowrider Bike Frames

Make a stencil of the tank shape out of a cardboard piece. (The tank is the piece of metal you plan to add to the bike frame using the Bondo.) Put the stencil on some sheet metal and trace the outline. Cut out the outline with shears.

Sand off some of the paint of the lowrider using a sanding wheel. Only sand off paint from the area where plan to apply the tank. Sanding will help the metal adhere to the frame. Lay the cutout sheet metal onto the bike frame to ensure it fits.

Spot weld the cutout sheet metal onto the bike frame. Pinch the metal onto the frame to provide a better attachment using vice grips.

Grind down the weld beads that naturally form from welding using a grinder. This process will render the sheet tight with the frame.

Sand the sheet metal with your sanding wheel to prepare the frame for the application of Bondo. This step will allow the Bondo to stick to the frame and will mitigate the dangers of the Bondo falling off or cracking.

Place a liberal amount of the plastic filler on a piece of cardboard. Add hardener to the filler at the correct ratio according to the instructions on the filler. Mix the two materials together with a small spatula until they turn a pinkish hew.

Apply the filler liberally over the tank. (Using an excess amount of filler on the frame is better than using not enough.) Spread the filler evenly over the tank, ensuring you hit all the corners, nooks and crannies.

Sand the filler using 40-grit sandpaper. Smooth out all bumps, lumps or inconsistencies.

Look over the finished product for and signs of lumps or imperfections. Keep sanding until the filler is flush with the surrounding metal.