Here is a job we recently did refinishing a complete set of wheels for a 1970 Lamborghini Miura. The original cast wheels are pretty rough on these cars; the appearance is that of a bad stucco job painted flat silver.
We started by dismounting the tires. Although it is certainly possible to refinish a wheel with the tire on, the amount of work needed in this case made tire removal necessary.
While the wheels could have been chemically stripped, we decided on media blasting. Glass bead had hardly any effect on the existing finish which had a kind of gravel guard consistency. I switched to garnet, a very aggressive material which will readily damage machined parts if improperly applied.
Even with the garnet the job took what seemed like a long time. An unexpected benefit was that the surface of the casting itself was considerably less rough when I was finished. The goal here was to re-paint not to metal-finish and polish to a shine. That would have taken several days per wheel. That said, I did want to smooth-out the rougher portions of the casting. I used my die grinder along with various sanding drums and rolls to carefully remove the high spots.
The other issue concerned voids and missing material. Some of the castings on the older exotics leave a lot to be desired. We have seen oil leaks in engine blocks caused by porous castings. I used ‘All-Metal’ to fill voids and chips. This is pretty tough filler that I think will stand up well to the abuse a wheel can see. Again, I was not trying for a perfect finish; I definitely left most of the original ‘character’ as it was.
After the filling stage, it’s pretty much standard refinishing work with a huge amount of inside corners. We love sanding them, don’t we? The backsides of the wheels were prepped for paint to the same degree as the fronts. Finished with two-stage polyurethane silver enamel.