This is a question for all you super tech guys. I have received a 26� wheeled tandem frame with a damaged dropout. I was just going to TIG a gusset to the frame and build it up. But we only have one bike left with 26� wheels, my daughter’s and that will be replaced with a 29� wheeled bike next season. I was thinking of changing the drop outs to use 29� wheels without moving the canti mounts. But to get the canti mounts lined up and have the tire running through the clearance area of the chain stays makes me position the wheel axle even lower than the existing dropout. This would bring the bottom brackets up high. I don’t have the exact measurement. But the 29� wheel automatically brings it up 1.5� (theoretically) and the axle location in the mock-up adds about 1.1� to this height. I hate to move the canti mounts but I think I will have to. Removing the mount from a 7005 series aluminum frame is what concerns me. If it was steel it would be a no brainer. Any suggestions or things I have missed?

If the new dropouts are located more backwards, the cantimounts at one point are in the right place again. Not sure if the angular difference between rim and cantimounts matters much. Very cool conversion project!

If the new dropouts are located more backwards, the cantimounts at one point are in the right place again. Not sure if the angular difference between rim and cantimounts matters much. Very cool conversion project!

I probably did not make this clear. Due to the radius of the 26” wheel that the frame was designed for, to get the tire of the 29” wheel to pass through the widest area in the chain stays and to pass by the cantilever mounts in the correct spot. Requires the axel of the 29” wheel to be set back about 1.25 inches and down about 1.1 inches. With the additional wheel diameter this raises the bottom bracket height to about 13.4”.

I understood, but still think that if you pull the rear wheel back enough, even if you place it higher in the frame, at one point the cantimounts will line up, though at a different-than-ideal angle with the rim.