- How to Restore and Powder Coat Wheels
How to Restore and Powder Coat Wheels
For some people, the parts that are actually "on" a car are what really make it stand out from the crowd. It could be that rare OEM accessory, those unique mag wheels, or a shiny aftermarket valve cover. Whatever it is, you wanted it because you knew the guy parked next to you at the show will most definitely NOT have it on his car. For some of us it's necessary, that is unless you have some sort of ultra-rare low-numbers car that speaks for itself all original. Otherwise, the rest of us tend to search the local classifieds, online auto forums, eBay, flea markets, yard sales, Craigslist, etc. for that "killer deal" on 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.
Possibly my biggest obsession is vintage aftermarket alloys or "rims". I think the correct wheel on a modified car can REALLY make a car stand out (in both good and bad ways!). Sometimes, I even feel this can make or break the overall "feel" of a vehicle. For instance, think of a guy at a show who has a classic older ’60s-’70s car, and he threw on some cheap, borderline-tacky chrome wheels he picked up at the local auto parts chain...it makes you almost cringe as he rolls into the show and parks next to the 100-point restoration car. This is why I often spend a lot of time picking out the "right" set of "summer wheels" for my cars (yes, I change them every summer). So when I went out to begin looking for a set of alloys for my daily driver 1984 Mercedes Benz 190e, I spent considerable time deciding on the "right" wheel. I mean, come on, I'll have to look at it every day in the parking lot at work! Not to mention, 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!
After a tip from a friend and a horrible eBay experience, I acquired a set of wheels that most of the European car community lusts for. These wheels were made by Ronal as a race-spec option to their common one-piece "Turbo" wheel. These wheels are a three-piece construction and have magnesium centers (these suckers are light!). With these wheels, you basically custom-ordered the wheels specifically for the car you wanted to put them on; you could pick any offset/backspacing, bolt pattern, width, etc. Ronal would simply assemble the wheels to your specs using different width lips and barrels. Since these wheels were quite expensive, and made specifically for dedicated race cars, making a set of these wheels fit a street car takes a bit of fiddling (and luck!). Before any of that, I had to work on restoring these wheels. They were off a ’70s Porsche road-race car, and had been sitting for some time. I was lucky that the original finish on the magnesium centers had protected the wheels a bit, and they hadn't begun to deteriorate like many old magnesium wheels tend to. You can see in the pictures below, these wheels needed some work!
There are a few different types of fasteners used to hold multi-piece race wheels together. Back in the ’70s-’80s it varied by company: companies like BBS used bolts with 12-point heads, while other companies used inverted 12-point bolts. Luckily Ronal used a simple socket head allen bolt to attach the wheels together. First you want to make sure you clean out the openings in the allen head bolts, as they have a tendency to strip the allen key opening out if the key isn't seated fully! Once all the bolts have been removed from the wheel, depending on your luck, the type of wheel, and if it has ever been apart before, the wheel should come apart into 2-3 pieces. Some multi-piece wheels used a very strong adhesive to seal the wheels and require the wheels to be pressed apart. Luckily these wheels originally used a metal seal with a rubber ring to seal them. This was nice because only a light tap with a rubber mallet was necessary to split the three pieces. In the pictures below 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 or major issues. Luckily they were all in satisfactory condition. It was evident that the wheels were definitely used for some time as dedicated race wheels. I concluded at that point I would need to fully blast the centers of the wheels, as the coating over the magnesium was not in the best of shape and there was minor deterioration beginning at the edges of the centers. Unfortunately these were a little too big for my own personal benchtop blaster, so I used our large blaster in R&D here at Eastwood. In hindsight, I would advise that if you are in the market for a blast cabinet, you go with one that is a size larger than what you "think" you will need. This is a perfect example...when I first bought a cabinet, I was only blasting and powder coating small engine and chassis parts. Now years later I am powder coating entire rear axles and wheel sets!
Once split, the wheels sat in my office at home for a few weeks while my indecisiveness over what color powder to cover them in passed. I finally got the time to bring the centers into work and make them look great again. I began by choosing aluminum oxide blasting media. Because the wheel centers are made of a fairly "soft" metal, I chose aluminum oxide over a traditional course-grit sand. While blasting, I made sure to hold the tip of the blaster about 12" to 14" from the surface of the wheel center, to avoid any major pitting or further deterioration of the metal. This process did take a bit longer than if I was blasting a steel wheel with straight sand, but when working with softer metals, it is necessary.
Another tip is to sift the media and reuse it. With the cabinet in our shop, it all falls down into the center of the cabinet, and is sucked back up with the gun. Occasionally I've found that you may need to drain the media 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 . In the pictures below, you can see these came out pretty nice with the necessary time and effort put into blasting them clean. Take note of the difference between a blasted center and a non-blasted center...cleanest they've been in probably 20+ years!
Once I was sure all the old paint, grime, etc. was blasted from the centers, I went on to clean the surface of each center, first with Chassis Kleen, followed by PRE Painting Prep, before beginning the process of powder coating. Chassis Kleen gets any major grease, dirt and film from the media off the surface, while PRE removes any last bit of residue from the blast media, as well as oils from my hands.
At this point I normally begin to wear rubber gloves to avoid getting any oils or grease from my hands on the wheels. I cannot stress enough that the key to getting a nice finish on anything you powder coat is to clean, clean, and clean again! You'd be surprised what a little bit of oil or grease from your hands can do to powder once it's curing. Most times that is the main cause of "fisheyes" and other common issues in cured powder.
I've found that because vintage alloy wheels see so much road debris, the metal tends to really hold onto that dirt and grime. This often gets baked into the wheels from the heating and cooling of the metal under normal driving conditions. I found it is a good idea to preheat the parts before spraying them with powder. Magnesium is known to be a very porous metal, so I was taking no chances of having any contaminants "outgas" when baking the powder. I've found that baking the parts to 350° for 20 minutes takes care of most of those issues.
This next part is a little tricky to do on your own, but if you prepare your work space ahead of time, it can be the key to a nice finish on the wheels. Immediately after removing the parts from the oven, you want to begin dusting them with powder. With the parts being nice and hot, you will find the powder sticks very well to the part, and may even begin to flow out before you put it in the oven.
I finally settled on our HotCoat Bronze Metallic powder. When powder coating wheels, I like to lay the powder on nice and thick, as these will see a bit of abuse from road debris. You can even see in the pictures below that the centers I had sprayed first (in the foreground) have begun to flow-out. It's cool when you see this, because you get a hint of what the finished product will look like!
After baking the parts for 25-30 minutes, I quickly pulled them out of the oven to inspect. At this point I was happy with the coverage of the color and was also assured there were no major "fisheyes" and no out-gassing had occurred. I then put the wheels immediately back into the spray booth and laid another nice thick coat of our HotCoat Super Gloss Clear Powder . Again, I baked the centers for the appropriate time, and removed them to cool. The clear is necessary on most of our metallic powders, especially if it is something that will see a lot of direct sunlight (as these wheels will). I actually think the clear powder really made the metallic in the bronze powder "pop", and left it with a nice smooth "wet" finish.
After getting the centers all nice and shiny again, I turned to polishing the outer lips of the wheels. Often these old multi-piece wheels came with polished aluminum lips, but if you didn't keep up with constantly cleaning the metal, they would get stained and the finish would become dull. Most racers aren't worried about how clean their wheels are, so these lips were no exception. They even had some old brake dust baked onto them. I decided to wet-sand the lips with 2000-grit paper to get the staining and brake dust removed. I then followed up with a set of our buff wheels and compounds on one of our benchtop buffers to get the surface of the wheel extremely shiny again. You can see the major difference just in the little bit of time I spent on this one lip! Once the wheels are assembled and complete, I usually go back and do one final polish with rubbing compound (more on that later).
Once all the major cleaning and polishing of the barrels and lips was done (some may choose to powder coat the barrels, but mine were in good shape), I began reassembling the wheels. As mentioned earlier, these wheels used socket head allen bolts. I usually install all the bolts with a dab of thread-locking sealant (I prefer the "lighter duty" stuff) and tighten each bolt down a few threads by hand first. Once all the nuts and bolts are mounted, you want to go around the wheel in an "X" or criss-cross pattern until all of the bolts are snug. For the final rotation, you then want to go around the wheels with a torque wrench and torque all the bolts to the proper torque. I've found a good torque for most three-piece wheels is 22-27 pounds. A lot of two-piece wheels actually have the barrels drilled and tapped, which results in the wheels requiring a torque setting at the lower end of those numbers.
Once the wheels were all bolted together, I ran a bead of silicone around the center of the wheel where all the pieces of the wheel meet. This is a "must" on wheels that originally came bonded together. The silicone is what actually makes the wheel airtight. Even though these wheels were not originally bonded from Ronal, I chose to apply sealer for peace of mind. I've found the original rubber seals on these wheels tend to get dry and crack, allowing the wheel to leak air. I choose to use Permatex brand sealant, particularly their high-temperature sealant that is black in color. I've found that it holds up quite well to the conditions inside a tire, not to mention it's easily available at any major auto parts store. I've found that one "caulk" tube will be enough to do 1-2 sets of wheels. The idea of sealing the wheel is to get a nice smooth bead with little to no pinholes (any pinholes in the sealant can allow air to leak).
I usually start with a thin bead around the entire center valley in the wheel. After laying the first bead, I run my finger around the center of the wheel to create a smooth, flat, even bead of sealant. From here, you want to allow the sealant to cure for 24 hours. After it has fully dried, you can now lay a second similar coat of sealant, again trying to make the bead as smooth and even as possible with your finger. You want to make sure any possible pinholes are covered and smoothed over. Again, let dry for 24 hours, and then you are ready to mount a set of tires!
Once I've mounted the tires, I like to let the wheels sit for a day or two (sometimes up to a week), and check the tire pressure periodically. Not much is worse than mounting a set of multi-piece wheels, and finding that one of your "seal jobs" was bad and you have to remove the wheel and reseal it!
For the final step, I like to do a final polish of the lips, and seal the finish to avoid any tarnishing from exposure to the elements. As you can see in the first picture below, those shiny lips are going to still have a slight haze to them after buffing, along with fingerprints and other grease that can make its way onto the wheels from reassembling them. I like to use two shop rags (one for application and one for wiping the surface clean), and Autosol Metal Polish for rubbing out the lips to a final mirror-like finish. You can apply/rub-in the polish and then wipe it clean numerous times, until you get the desired shine. Hard to mess this step up (other than just making a plain mess everywhere!). Autosol really brings out the shine in polished metal, and finally makes all that sanding, buffing, etc. worthwhile!
Once you wipe all the remaining Autosol off, you need to prep the surface with PRE Painting Prep to get the lip ready for a sealer. Recently we came out with a product designed to help you avoid repolishing the shiny bits on your ride so often. I wanted to give it a try, as I absolutely loathe the process of repolishing my wheels every time it rains, or after a long drive! This product, Metal Protect, uses the newest nano-barrier technology to coat and seal polished metal, all while being nearly undetectable once dried. I was a bit skeptical, since it comes in a aerosol can, and I just pictured myself spraying it on and it looking like bad "clear coat". Luckily the Metal Protect was designed to self-level. This means that it smoothes out as it dries. The key to applying I found, was to spray on two light "dust coats". You can see how in the first two pictures it seems like it is going to dry very textured, but by the end, it smoothed out quite nicely. I will admit I did lay it on a little thick in spots, and I can see some minor orange peel up close; in retrospect my second coat should have been much lighter.
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 (the heavy downpour the night before didn't help!), 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, but I am sure this would work great on engine parts and exterior trim.
I hope this article has given you a small insight into the procedure for restoring old alloy wheels. If you have any questions about a part of the procedure that I missed, or you want clarification on something, feel free to post a comment! Below are a couple pictures of the wheels finished and on the car from the show I mentioned above. Thanks for reading, and keep scouring those flea markets and swap meets for parts!
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