Refinishing

All drums have a maximum diameter cast into them. This diameter is not a refinish diameter. Do not refinish a drum that will not meet the specifications. Any drum that does not meet specifications shown should be replaced. When refinishing a drum, resurface the drum to no more than a dimension of 0.76 mm (0.030 inch) less than the discard diameter. The refinish diameter is the maximum diameter the drum should be refinished to, and still allow safe braking action. If this dimension is exceeded, the drum will wear beyond the discard diameter during normal brake wear. If a drum must be refinished, remove only enough metal to obtain a true, smooth braking surface. If a drum does not clean-up when refinished to a maximum rebore diameter as shown at the end of this section, replace it. Removal of more metal will affect heat dissipation and may cause rear brake drum distortion. When refinishing drums, always use sharp cutting bits. Dull or worn bits leave a poor surface finish which will affect initial braking performance. Anti-chatter silencers should always be used when refinishing braking surfaces. These silencers eliminate tool chatter and will result in a better surface finish. After making the finish cuts, sand the brake drum friction surface for at least 60 seconds. Use 150 grit aluminum oxide sandpaper on a curved sanding block. Make smooth in-and-out motions with the block while sanding. This procedure will simulate the original factory surface finish.