How to Restore and Powder Coat Vintage Modular Alloy Wheels
For some people, the add-on parts on a car are what make it stand out, whether an OEM accessory, those unique mag wheels, or a rare aftermarket valve cover. Whatever it is, you wanted it because the guy parked next to you at the show most definitely will NOT have it on his car. That is unless you have some sort of all original, ultra-rare low-numbers car that speaks for itself. Otherwise, the rest of us tend to search the local classifieds, online auto forums, eBay, flea markets, yard sales, Craigslist, etc. for that perfect part to finish off your project.
There are many different options when it comes to the restoration and modification of your vehicle. Personally, I'm a nut for old vintage aftermarket parts for the European vehicles I tinker with. Anything from old race parts, to retro steering wheels, to literature...I'm constantly seeking out rare old pieces of history from these cars. My biggest obsession is vintage aftermarket alloys rims. The correct wheel on a modified car can REALLY make a car stand out. This is why I spend weeks picking out the right set of "summer wheels" for my cars (yes, I change them every summer). So when I was looking for a set of alloys for my daily driver 1984 Mercedes Benz 190e, I took my time waiting for the "right" wheel. I'll have to look at it every day in the parking lot at work! I can't be a laughing stock, rolling into work with tacky chrome wheels from the local auto parts store...I'd never live it down!
Based on a hot tip, I acquired a set of wheels that the European car community lusts for. These wheels are not the typical 1 piece Ronal "Turbo" wheels, these are the race-spec three-piece version with magnesium centers (these suckers are light!). The modular 3 piece nature allowed you to custom fit them: Any offset, bolt pattern, width, etc. Ronal assembled the wheels to your specs using different centers,lips and barrels. Originally quite expensive, and made for dedicated race cars, finding a set to fit a street car takes a bit of luck. Mine were off a ’70s Porsche road-race car and had been sitting, but luckily the finish on the magnesium centers had protected the wheels and they hadn't deteriorated like many old mag wheels tend to. But, these wheels needed some work!
Disassembly and cleaning
Back in the ’70s-’80s, different companies used different hardware on their 3-piece wheels. BBS typically used bolts with 12-point heads, while some others used inverted 12-point Torx bolts. Luckily, Ronal used a standard allen bolt. First clean out the heads of the allen bolts, as they have a tendency to strip if the key isn't seated fully! Once all the bolts have been removed from the wheel, the wheel should come apart into 2-3 pieces. Some multi-piece wheels used an adhesive to seal the wheels and need to be pressed apart. Luckily again, Ronal used a metal gasket with a rubber ring to seal them so only a light tap with a rubber mallet was necessary to split the three pieces. You can see how the center of the wheel was stuck in the outer lip of the wheel. A couple taps of the mallet quickly separated the parts.
After splitting the wheels, I took some measurements and inspected them for any damage. It was evident that the wheels were definitely used for racing at some time but they were structurally sound. The centers of the wheels would need blasting, as the coating was not in the best of shape and there was minor deterioration at the edges. This is a perfect example of why you should buy the next size up blast cabinet than you thnk you need, so I have to do it at work, at Eastwood, on my lunch break.
I choose to use aluminum oxide blasting media, because the wheel centers are made of a fairly soft metal. I made sure to hold the tip of the blaster at least 12" from the surface to avoid any major pitting or texturing of the metal. It did take longer than if I was blasting a steel wheel with straight sand, but these are rare, soft, alloy parts.
TIP: Sift the blast media and reuse it. Drain the media periodically and sift it to separate all the dirt, grime, paint flakes etc. This is a good precaution to prevent the gun from clogging up and causing problems.
After blasting 20 years of grime and grit off of them they were looking pretty good. Next I wiped them down with PRE painting prep to remove any last trace of grease and oil from the surface. If they were really grimey, there is always Chassis Kleen to blast through the toughest crud. At this point you are going to want to wear gloves to avoid the clean metal absorbing oil from your skin. The key to a good finish is the start with a clean surface!
Prepare and Preheat
Wheels live a hard life, and even if they look clean they may not be. Magnesium is known to be a very porous metal, and oil and other things can "outgas" when curing the powder, possibly ruining the finish. Baking the parts to 350° for 20 minutes takes care of most of those issues.
The next part is tricky to do on your own, but it can be the key to a nice finish: immediately after removing the parts from the oven, dust them with powder. You will find the powder sticks very well to hot parts, and may even flow out a bit. When powder coating wheels, I like to lay it on nice and thick, as these will see a bit of abuse from road debris.
Spray on the Powder and CureI finally settled on our HotCoat Bronze Metallic powder. You can find detailed instructions elsewhere on the Eastwood blog, YouTube channel, or How To Center on ho to actually spray on the powder, I'm not going into the details here. Apply the power, then carefully place the parts in the preheated over. You can see in the picture that the wheel centers in the foreground have begun to flow-out. You can already get a hint of what the finished product will look like!
After baking for 25-30 minutes, I pulled them out to inspect. I was happy with the color coverage and finish, so I immediately the centers back into the spray booth and laid another nice thick coat of HotCoat Super Gloss Clear Powder . Clear is necessary on most of our metallic powders, especially if it is something that will see a lot of direct sunlight to prevent tarnishing ans discoloration. Then it was back in the oven to cure the clear.
Polish the Lips
Next up is polishing the outer lips of the wheels. These old race wheels still had brake dust baked onto their formerly polished aluminum lip. Start by wet-sanding the lips with 2000-grit paper to get the stains out, which is probably enough for the inward lip for the wheel which you'll never see. Follow that with a set of our buff wheels and compounds on a benchtop buffers to get to a polished aluminum look. This part of the job can get really dirty and is time consuming, but it is so worth it to have that mirror finish aluminum contrasting against that darker center.
Putting it All Together
Once all the major cleaning and polishing of the barrels and lips was done (I choose not to powder coat the barrels, since they were in good shape), reassemble the wheels. Get all the bolts started by hand, then use a dab of thread-locking sealant. Go around the wheel in a criss-cross pattern until all of the bolts are snug. Finally, torque all the bolts to the proper torque, about 22-27 pounds in this case. Many two-piece wheels have the alloy barrels drilled and tapped, which requires a lower torque setting.
Seal it up
Once the wheels are all bolted together, run a bead of silicone around the center where all the pieces of the wheel meet. This is a must on wheels that originally were bonded together, and a good idea on all the rest. Even though these wheels were not originally bonded from Ronal, I applied sealer for peace of mind. The original rubber seals on these wheels tend to get dry and crack, allowing the wheel to leak air. The idea when sealing the wheel is to get a nice smooth bead with no pinholes. After laying the first bead, run a finger around the center of the wheel to create a smooth, flat, even bead of sealant. Allow the sealant to cure for 24 hours, then lay a second similar coat of sealant.
Let the 2nd coat dry for 24 hours, and you are ready to mount a set of tires! Once you've mounted the tires, let the wheels sit for a day or two (sometimes up to a week), and check the tire pressure. I can be a real pain if after than mounting a set of multi-piece wheels, you find that one of your "seal jobs" was bad and you have to remove the wheel and reseal it!
Final Polish and Finish Sealer
The final steps are to grab some Autosol Metal Polish and rub out all the smudges, finger prints and anything else left over from mounting the tires and bolting the wheels back on the car. Autosol really brings out the shine in polished metal, and finally makes all that sanding, buffing and polishing worthwhile!
Before sealing your work, you'll need to wipe it down one last time with PRE Painting Prep to get the lip ready for the Metal Protect sealer. Metal Protect uses the newest nano-barrier technology to coat and seal bare polished metal, all while being nearly undetectable once dried. You may be a bit skeptical, since it comes in a aerosol can, and you may be expecting bad "clear coat". But Metal Protect was designed to self-level, so it smooths out as it dries. On the protecting side of things, it is based on chemicals and formulas originally invented for military applications, so you know it is tough enough for your wheels.
After I got the wheels polished and sealed, I took my car to a local car show. The show was held in a large grass field, and I had to drive on a muddy, stone road to get to the show field, so the Metal Protect was immediately put through its paces. I am happy to report that after the weekend show, I came home and washed the car like normal, wiped the wheels down with a microfiber cloth, and they still look great! No water stains or hazing that I would normally have to polish out after a heavy storm! The jury is still out on how long it will hold up on my daily driver.
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