AMG Wheel Lip Repair
Here I'll try and take you through repairing the wheel lips on an AMG rim. It's unfortunate when wheel damage happens, whether you blame it on your wife or not, but most people don't know it's pretty easy to repair with just a few tools, a few hours and some patience. This repair is only for wheels with a CNC-machine finished aluminum clear-coated lip, like most modern wheels on MB's today. If your entire wheel is painted, then repairing your wheels is even easier with a little filler and paint, but that's for a different article. When we're through with this repair, the wheel lip will be fully polished and shiny almost like chrome. You can choose to clearcoat the entire wheel when finished or leave it as is with the bare polished aluminum. If you choose to leave it bare you'll need to be very careful when cleaning the wheels not to use any harsh chemicals or you will damage the surface and oxidize the aluminum, making it very dull and needing polishing again. I recommend getting the entire wheel professionally clearcoated for a durable and factory looking finish, unless you have access to paint equipment and a bake booth to do it yourself.
Above you can see the damage to the wheel I'm using as an example. This wheel has some pretty bad damage but I've fixed much worse. AMG wheels in particular are built very sturdy and have very thick wheels lips, which leaves you a little room to grind away some of the lip without sacrificing safety and the integrity of the wheels.
Above you'll see the basic tools you'll need for this repair: a grinder (either air-powered or electric) with 80-grit sandpaper or grinding disc, non-stick masking tape, a water squirt bottle with a soapy water solution, metal polish of some sort (Mother's aluminum polish or 3M rubbing compound both work very well), and sandpaper in 320-grit, 600-grit, and 1200-grit. The first thing you'll need to do is get the wheel off the car and have the tire dismounted from the wheel. Tape the entire inner wheel section that has a grey painted surface so you don't damage it during grinding and sanding. Be sure to keep the tape very precise with a fine edge at the seam where the painted surface meets the CNC-machined section . You may want to use a razor blade to cut off the rubber valve stem if it's in your way of repairing the lip. After the wheel is completely taped off, it's time for grinding. AMG wheels have a very thick clear coat on the entire wheel and we'll be grinding that off as well as grinding away the scratches and nasty curb rash. While grinding you want to keep moving and don't concentrate on one area for too long or you'll create a low-spot in the lip which will give it a warped/wavy look when finished. You want to keep moving the grinder in a steady fluid motion around the lip of the wheel. You also want to keep the lip in a rounded shape, so don't grind too long on a flat plane. I usually use a spinning tire machine that rotates the wheel and I hold the grinder still to keep a nice uniform grind, but if you're working on a bench you'll just need to be smooth. Grind the entire untaped area of the lip. You can see a good example of a nice smooth grinder pattern on the picture below left.
In the picture sequence above you can see the transition from grinding to hand sanding. Once you have finished grinding the clear coat completely off and removed all the curbing scratches it's time for hand sanding. With 320-grit sandpaper you want to sand with the rotation of the lip, sanding in a straight motion (see pics above). You need to sand until all of the grinding scratches are gone. This is the longest part of the job, usually taking an hour to an hour and a half, but you don't want to cut corners here because when you polish the lip later those scratches are magnified and it will look horrible. Once you've sanded all of the grinding scratches out with 320-grit, it's now time to start wet-sanding with 600-grit. Only wet sand in small 4-5 inch sections, spraying the soapy water solution on the lip and hand sanding in the same direction as the 320-grit. Wipe the lip dry routinely to clean the surface of debris and check your progress, then spray again and continue wet sanding. The more time you spend wet-sanding the 320 scratches out, the better your overall finish will be when you're done. It usually takes about 15-20 minutes to complete the lip with 600-grit. Once you've completed with the 600-grit, then continue the same wet sanding process with 1200-grit to remove the 600-grit scratches. The 1200-grit sandpaper is very fine and clogs with debris quickly, so be sure to use a lot of soapy water and clean it often, otherwise you may be doing more harm than good. The 1200-grit step usually only takes 5-10 minutes.
Once you finish with the 1200-grit step you are ready for polish. You can do the polishing by hand or use a small buffer pad, I usually do it by hand. It usually only takes 10-15 minutes for polishing. I usually use Mother's aluminum polish with a terry cloth towel. Apply some polish to the towel and work the polish into the metal by rubbing it onto the lip just like when you were sanding. The polish will turn to a dark color and that's when you know it's really starting to work. Work the polish in small 4-5 inch sections until it is nearly dry and then let it sit for about 2 minutes to dry. Then wipe it off with a clean towel and check the finish. If it looks to need a little more polish then repeat the process until you get the desired finish. The more you polish the better it will look. When you've finished polishing you're ready to install and new valve stem and remount and balance the tire. If you're choosing to clearcoat the wheels you'll want to have that done before you mount the tire. I only recommend clearcoating if you have it done professionally and have a quality automotive paint sprayed and baked on because the spray cans on the market are not very good quality and will chip easily and turn yellow with the heat of the brakes after time. Above is a pic showing the finished wheels on my '87 190E-16v. As you can see the results are very shiny and look better than the factory finish in my opinion.
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