Shortly after deciding on my short reach/tall stack/fat-tire design, I started rooting around to see what bits and pieces I have for such a build. One bit which drew my attention was a 1980's 21" Shogun 500. After playing around with my trusty ruler and CAD a bit, I determined that if I could swap in a 230mm head tube I could get very close to the reach/stack which I was hoping to build (within 5mm). So that was good, but what about the tire clearance? It had 50mm clearance for 559s, so it was in striking distance. BB drop was right where I wanted it (slightly higher, actually), so it seems like a very good practice candidate to hone my frame modifying/building skills.
After a bit of hand-wringing around the matter, and playing around with the ruler some more, I pulled the trigger.
I first removed the bridge between the stays, and then used a hardwood wedge to expand the stays out to 65mm, with the goal of a 55mm tire. I drove it in with a hammer, which seemed to go okay:
I wish I had measured things a bit more before clubbing away...it would be nice to know where the bending is actually happening. There is no obvious, abrupt deformation, so I am feeling all is well.
Now, all I needed was a 360mm wide hub and things would be great. Unfortunately, there were none around, so I bent the stays back in line, around a 65mm diameter block:
I used the threaded rod to get the drop-outs pretty close to 136, then I bumped it with my fly press around the wood block to set it. Looks decent and fits some 2.125 knobbies:
The stays are 443mm, so the bend is pretty slight. I am hoping my bend is in the correct place for non-knobby tires (I think it is right at 12"). I put on a triple crankset and there is plenty of clearance, so things seem good there too.
Next step is to rotate the TT about 15degrees up and install a taller head tube. Due to the angle of the HT, I should be able to reuse the existing top-tube if I can keep the whole thing. I think I am going to cut the HT and see if I can un-braze it from the ST. I'll file down the lug and fillet braze the TT. If I can I will reuse the existing DT lug.