Duplicating original finish on 80s BBS wheels

[G50]

I’m restoring a set of BBS RS wheels.
I’m trying to duplicate the original finish on the lips.
I believe they were “machine finished” then clear coated.
The machine finish puts a satin finish with very tiny grooves that at angles gives a slight rainbow effect. Kind of like a CD disc.
I’m having a hard time finding a shop that can do a machine finish.
Second best would be to at least come close to duplicating the original sheen.
The problem I’m having there is polish shops say they basically have to mirror finish them or they’ll look uneven.
What I don’t want is a mirror finish or chrome look.
Whatever finish I get, I’ll be clear coating.

Here’s the disassembled polished lip now (middle picture) along with a pic of the look I’m trying to duplicate.
Any thoughts?

[Shaun @ Tru6]

The rainbow effect could indicate they are anodized. Can you see or feel a coating or is the surface similar to Fuchs?

[Superman]

It looks like the polish I see on crank journals, which is actually a rough texture when seen under sufficient magnification.

[G50]

Definitely not anodized. The original clear coat comes off easily with paint stripper, and the aluminum underneath is then easily polished.

Yes, the “machine finish” would have a rough texture under magnification. That’s what gives it its satin sheen.

[jyl]

Can you put the rim in a rotating jig and use various grades of sandpaper? Kind of like how DIYers restore brushed stainless steel finishes. Maybe test it on the backside.

[ADDvanced]

Yeah man... good luck. I have a mint RS and the rainbow effect is very apparent, and looks incredible. I have not found a shop able to replicate it.

[Zeke]

Try various Scotchbrite grades. Gray is very fine, you won't hurt it with that. You need to spin the rims to get an even effect. You could do this on an axle with a fixture but the speed has to be constant. And somewhat low. I'll throw a number out there for grins — 50 RPM. So a tire balancing machine might be too fast (and dangerous). IDK how you're going to mount just that part. Change your pad around often and they wear and load up.

I guess I'd cut a plywood circle and secure the rim with screws that were barely proud of the surface. You might have to change screw locations to get an even sheen right at the bolt circle.

If I had (you had) a big lathe, no problem.

[ADDvanced]

I think that will just result in a brushed appearance, not the rainbow effect of the original.

[Shaun @ Tru6]

I think the only way to get a machine finish is to bring(maybe just) assembled halves to a wheel refinisher to put them on a lathe. And then won't get the area with the bolts. I imagine BBS has an expanding drum lathe for wheel halves to create the finish or more likely, it's a manufacturing artifact of the barrel making process.

[908/930]

If the surface finish process was machined (turned) and then coated it will be hard to reproduce, sort of like trying to refinish an old Vinyl LP, the tool leaves small chatter marks as it removes the aluminium. Know anybody with a large CNC lathe?

[herr_oberst]

[QUOTE=Shaun @ Tru6;11930330 I imagine BBS has an expanding drum lathe for wheel halves to create the finish or more likely, it's a manufacturing artifact of the barrel making process.[/QUOTE]

I'm pretty sure there's also a proprietary chemical finish used to get that iridescence. Maybe not anodizing, maybe just a h/d industrial coating, but in my opinion there is more to that final look than the final scratch finish. Just my opinion.

[jyl]

Maybe approach it the other way - find a coating or other surface treatment that creates the iridescent effect.

[908/930]

Originally Posted by jyl

Maybe approach it the other way - find a coating or other surface treatment that creates the iridescent effect.

I was thinking this could work, possibly some silver pearl in the first coat of clear? That rim now being full polished do you plan on sanding that back down to 320 grit or so to paint with clear coat?

[sc_rufctr]

This popped up as a recommended video. I haven't watched all of it but it looks good.

(I've never restored BBS RS wheels)

[G50]

Originally Posted by sc_rufctr

This popped up as a recommended video. I haven't watched all of it but it looks good.

(I've never restored BBS RS wheels)

Yes, what they did on those was exactly what everyone does - polish the lips to a mirror finish. As I’ve discovered, when polishing by hand machine like that, you have to go mirror finish to get the scratches out uniformly (it’s impossible to polish like he’s doing and get anything close to a uniform non mirror finish).

Zeke, scotchbrite on a lathe might work. I thought I couid have the polisher just use a slightly rougher finishing paste, but that didn’t work because the finish could not be made even enough by hand. It looked really bad. Spinning on a lathe might work, but (1) I have some doubts, (2), there’s the issue of the bolts and (3) I don’t have the equipment and I think it would be hard to find someone willing to try that for me, it’s a lot of work. (Also, I think scotchbright might be too rough. I polished part of it with 5000 grit wet paper, and it absolutely killed the sheen).

Shaun, yes, a machine finishing lathe would work, I think that would be duplicating the factory method, but every machine shop I talked to had no interest or ability to do it.

Jyl - some kind of a spinning jig might work, but similar concerns as above re Zeke.

908 and others - yes, my current thinking is to try to make the effect in the clear coat. There’s 2 different effects, the slightly matte finish, and the iridescence. I think I can probably get an acceptable matte finish by using a satin clear instead of straight clear. That probably gets me 90% to where I want to be.

I was thinking a touch of pearl maybe, but I don’t think that would be right. The finish isn’t really a pearl finish, the iridescence comes from the machining, it’s very similar to the finish on a CD disc (although much finer).

[G50]

I have another set of BBS wheels on my car that someone refinished.
They aren’t machine finished, they polished them and applied some kind of clear.
I thought it was just straight clear, and maybe that clear dulled it down a bit, but I test shot one of my polished RS lips, and the clear didn’t dull it down at all.
So now I’m guessing they used some kind of satin clear on the lips.
But then I start to doubt it, because the spokes are definitely a shiny clear clear, and it doesn’t seem likely that most restorers would take the time or care enough to use two different types of clear when shooting the wheel.
(My theory is maybe the polished lips, even though they are cleared, continue to dull down naturally. I have no idea of who did, or when those wheels were restored).

[Zeke]

You can try the Scotchbrite on the CC. Light touch. YOU can't do this by hand.

I told you how to avoid the bolt but you didn't read it.

Sometimes we use brown paper bags on antiques to soften the finish.

[flatbutt]

Just a WAG but if the original was machined to have a regular pattern of grooves which may approximate a diffraction grating then I don't know how you can replicate that by hand.

[G50]

Zeke - I see. Yes, a couple small headed bolts would hold it together good enough to spin the wheel up. Spinning and dulling with something very fine, like a brown bag, or some kind of coarse rubbing compound, might work. I don’t have a lathe, if I did I’d definitely experiment. Even in So Cal I’m finding it hard to find a shop that wants to do it, or even try.

FB - I agree, i don’t think it could be replicated by hand. It would have to put on a lathe and machined to truly duplicate it.

[908/930]

G50, know anybody with an electric motorized pottery wheel? Do you have a piece of aluminium sheet and some clear to use to try different surface finishes, if not time to pick one up. One thing about polishing/sanding aluminium, you need to constantly get rid of any aluminium dust before it becomes part of the grinding process.