Pletscher customer service is on-point. Kudos to them for sending me these measurements on their adapter. Posting here in case anyone else has this question in the future.

Thanks, good to have.

I notice they don't give you what is arguably the only measurement we need, the inside width, which should match up with the outside width of the braze-ons on the frame.
We can infer it from the measurements they do give though, looks to be 58.5 mm. Is that anywhere near the BO width on your frame?

The BO width can be narrower if you don't mind a stack of washers to make up the difference. But beyond just a few washers, that's ugly and structurally inefficient. The frame can't be wider than 58.5 mm though, not without unbending and re-bending the adapter.

Probably easier to just make one, out of suitable steel, just two bends and 4 holes. Stainless is harder to work with, but has the advantage of not rusting, so that's probably what I would make it out of. I'm happy to provide more tips like where to buy stainless, how to drill it etc, ask if interested.

+1 to getting a Blackburn. I had a Pletscher on my first 10-speed, a Schwinn Continental. It attached via the infamous sandwich clamp, and swayed in the breeze with any sort of load. That's a good bike/rack match, as neither are very good but both are classics from the same era.

I hear you. You are on the right track, then. As a fellow Technium owner, big check on the "coming apart" comment. Keep looking down. On the other hand, I've ridden mine since new, in 1990, and it is indestructable. I wish I could get my Pletscher that shiny. I may get out the dremel.

Since it bugs me to no end to search for threads like this and the OP doesn't post an update or wrap-up, I'll make this a two-part ending since I'm waiting 24 hours for the paint to harden on my adapter.

What I started with...a piece of bar stock mild carbon steel that's (somewhat) easily bendable. Available at any hardware store for around $5.




After measuring, bending, drilling, filing and painting, here's what I came up with:





Will post a final pic on the bike after the paint has properly cured. This piece is pretty strong too...I'll certainly worry more about the Technium imploding than I will the rack coming loose.

I deferred 58.5mm inside width myself and unfortunately the OE adapter was too narrow for the Raleigh. So, it set me to work on making my own since there was no clear OE solution to be had.

Final prototype. For this bike it just may well be good enough. I was planning to make one out of SS, but I painted this one up and clear coated it and it turned out very decent. It's certainly strong and the rack isn't going anywhere. It is the least "hardware store" I could come up with, even though it's 100% hardware store. The allen head 'water cage' bolts do help it look more like an OEM piece, I suppose.

Kudos, I love it. The weight weenie in me might have shortened the extension forward of the bolts into the braze-ons, and rounded the ends, would be several milligrams lighter

I hear ya. I was going to chop the extra length off and grind them after I had the rack alignment down (and drilled accordingly) but I really wanted to just be done...especially if this frameset implodes after the first ride. Figured if I make another set out of stainless I will adjust the length accordingly.

I don't mind the little extra overlap aesthetically as it hides the rack bosses. I stopped caring about weight several years ago as I've passed over or sold off "heavy" parts that I'd now love to have back.