Wow, another example of ever changing "standards" that drive DYI'ers crazy. So I've been emailing and chatting on the phone with tech reps at MRP who makes the ISCG-05 adapter I want to get. I tried to explain over the phone that there isn't a spacer between the drive side BB cup and the frame but there is one between the BB cup and the chain ring. Since that adapter is designed to replace a 2.5mm spacer that's normally there he was a bit confused until I sent him that picture above of my BB. He did some investigating and replied with the following below:
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Tony,
I just finished doing some digging into this, and found it’s the new system for DUB BSA bottom brackets, and under the radar change that would only be noticed if you work in a shop or have swap from the old to new in more recent times. But, as luck would have it, I had to idea to check my new bike that came yesterday to see if I could compare the old and new system in person, and sure enough. My bike from last year uses the older BB style for DUB, and my new bike uses the Dub BB that you also have, so I was able to experiment with chain line and modifications.
Here's what I found:
That spacer on the outside of the BB cup you have is 4.5mm and a specific bearing seat, the old style was just a plastic cover that was flat with a 2.5mm spacer, and what appears to be a slightly wider BB cup. So to find a way to make an ISCG-05 adapter work with the new bottom bracket, I removed the 4.5mm spacer and tried both a single 2.5mm spacer behind the BB(which did not pick up enough space for the crank to cinch down without play) and 5mm total of spacers (which amazingly resulted in too much drag when tightened enough to remove play) .
I’m getting the sense that this new style does not play well with our ISCG adapters either. The only other approach I can think of is finding a 2mm spacer to pair with a 2.5mm spacer, but I don’t see that as a guaranteed method for success since the 4.5mm also has a unqiue bearing race to it.
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I think the unique bearing race is the problem. I think I'm going to take it apart so I can see what is so unique about it. Fun stuff.