Just got back from a ride and noticed a crack in my steel single speed mtn bike. Looks like I was using a seatpost that was too short and it punched its way through the tubing. I haven't stripped the paint, but you can see the crack as a black line on the seat tube.
I'm wondering what people's opinion might be for trying to fix it by brazing the joint. I was thinking of brazing the crack, then fashioning a "patch" over the spot and brazing that in. Would that be strong enough or is the frame dead? Its not worth replacing the whole seat tube I think. It might look a little funny but that's ok. Obviously afterward I'll run a super long seatpost to add strength to the spot.
there is no point to doing anything to the tube other possibly tig welding it. I have thought about putting two gussets from the seat stays to the top tube in situations like this. Alternatively, You could add a sleeve around the top tube. I have no experience with either repair. The fundamental problem with this frame is that they didn't reinforce the seat tube. There are actually a lot of stresses passed through from the seat stays to the top tube, and that will crack something, usually the seat tube. That's why bikes that are built to last either have a sleeve there or an externally butted seat tube.