Tuesday, February 27, 2018

Around the Rim (Part 3)

Today's post continues the saga of upgrading the rims on the '78 MGB from the crummy chromeys to some mid-90's Honda alloys.

Clean, Clean Again
original Honda rims
After 30 years of use, and very little in terms of care, these new-to-me rims needed some love. First, they needed to be cleaned. I started with some basic car wash, a scrub brush and a hose. This worked some, but there was some stubborn brake dust and other grime on the insides. This took brake cleaner and some 150-grit sandpaper, but I was able to get down to some silver. I washed them a third time, this time with dish soap and a scrubby sponge in my kitchen sink (Boo puts up with so much). Once cleaned up, we could really get a look at what I'd bought.

Assess the Damage
Two of the rims were in fairly good condition. There wasn't much in terns of curb rash around the outer edges, and there were only a few scrapes from what looked like applying snow chains. The other two rims, however, had been in a few fights. There were some small chunks chipped out nearest the rubber, and many many gouges in that outer edge as well. Sadly, there were some deeper wedge-shaped scrapes in the face where, again, it looked like the rubber strap for tire chains had been put on possibly wrong such that the loops dug into the rim.

Plan the Work
The damage, though, was purely cosmetic. I was able to add air, and the air held in all 4 tires. Since the damage was surface, I knew I could repair it, but I felt I would need to paint rather than restore to plain aluminum. I'm sure there are others out there who can repair aluminum such that it looks like the damage was never there. That's not me.

paint concept (upper right)
To fix the chips and gouges, I thought about brazing alumi-weld into the gouges, and then polishing. Alternatively, I could use Lab Metal. I've used that stuff before, and it really does finish nicely, but I'm not convinced that it will leave the exactly right color. I suppose I could mix aluminum dust from sanding the rim into the mix for coloring if I really wanted to retain the all-aluminum look. After looking at the rim on the car, I think adding some color would look better, especially since there is a very limited amount of chrome on the car.

So, I planned to repair the chips and gouges with Lab Metal, and paint the outer lip and the mag-face, leaving an inner rim and the insides of the mags the original aluminum. This would bring out some of the chrome while not having an overwhelming amount of it. I mocked up a few options in paint so I could get a sense of how it would look and then I got started. First, you need to get down to the bare aluminum.

Take off that Clear Coat
on-car paint concept
The Interweb is a great resource, but some advice just isn't that good. While some is wrong, other advice can just be ill-suited to either your skills or project. For example, there appear to be many folks advocating removing the factory clear coat by sanding until what you're removing shifts from white to grey. Then you know you're down to the aluminum. While this does work, it takes an incredible amount of time. If you try to short-cut the time by using a lower grit (like 60 instead of the recommended 100), the car part will get deeper gouges that need to be sanded off with higher grit. In the end, I'm not sure if much time gets saved. I tried this method with one wheel. Since clear coat is not applied uniformly, you will hit grey while also still removing coating. In the end, I think this method was a bust, and don't suggest it.

For the other 3 rims (and I came back and did the sanded rim too), I used airplane stripper. C had some from when he was stripping the paint off the 280ZX, so I knew it worked and worked well. At least on paint. I knew that it didn't damage rubber when little drips got on it. I laid out the three rims, and brushed stripper on one wheel at a time. Once I got done brushing the third rim, the first was about dry, so I applied a second coat. Doing all four wheels would have timed out just about perfectly. Once the second coat was dry, I attacked the rims with steel wool. The clear coating scrubbed right off, leaving the bare rim with little flecks of clear coat left behind. To get completely cleared, I used a razorblade scraper. The airplane stripper was significantly faster and left behind a better surface. I hosed the rims off, and they were ready for the next step: fixing the damage. I'll get into that next time.

Thanks, as always, for following along. More next time-

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