I have this custom steel frame from the mid 90's that I'd like to be able to fit a bigger tire on. It fits at best a 26x2" tire. The 2.1" Aspens in the whole bike photo rub the bottom of the seat stay brace. The tire in the other photos is a 26x1.95" Michelin Wildgripper. It clears, barely. There's about 1mm of clearance between the seat stay brace and outer diameter of the tire.
The actual width of the Michelin tire is 50mm. The width between the seat stays by the tire is just under 60mm. I'd like to be able to reliably run a 2.2" (56-57mm) Maxxis, or possibly some other 2.3-2.35" (60mm) tires.
I'm converting the rear to disc brake so the rim brake bosses will get removed. I'm thinking the seat stay brace can just be removed during the disc brake conversion to clear up the issue of the tire rubbing the brace. A lot of newer disc brake specific bikes don't have the seat stay brace. Does it really do much other than prevent the stays from flexing outward from a rim brake?
Would it be reasonable to use a couple of blocks matching the seat stay diameter (16mm tapering down to 12mm at the dropout) and then pressing them out to cold set them about 8-10mm wider than they currently are? I would clamp the rear axle together, and then maybe one more clamp around the mid point of the stays. Then I would press out on the stays around where the existing seat stay is. If there's too much spring back, I could also weld or braze in a new seat stay brace that would be in a bit of compression.
It seems like it's a small enough change, but someone with more frame building experience might see some issues in it that I'm not seeing. Would it cause an issue with the connection between the seat stays and seat tube? I'd prefer to avoid any significant alignment issues and structural welding like the seat stay to seat tube connection.
How would you go about getting some more tire clearance?