Hello all. I have a trek 400 frame with a dent on the down tube that is pretty significant. I got the frame for free so I think I am going to give replacing the tube a shot. I did some googleing and could not come up with any clear directions on how to heat and remove the tube from the lug or how to clean out the lug for the new tube. I have access to a shop that has the tools necessary to do this, as well as people who have the knowledge. I am just looking for directions or something so I can go in there with a good idea of what to expect. Thanks for your help

HERE's (http://www.yellowjersey.org/zito.html) a link showing replacement of a head tube, but the sequence for replacing your down tube will be similar.

To remove the dented downtube without damaging the lugs, first cut the down tube in half. Coat the lugged joints with boric acid flux, then evenly heat the down tube/lug joints one at a time using a big cool oxygen-propane torch. Heat the entire joint evenly so that the tube can be pulled from the lug without damaging the lug.

If the joint is pinned, you'll have to cut the downtube close enough to the lug so you can reach the pin with pliers and pull it out while the joint is being heated.

HERE's (http://www.yellowjersey.org/zito.html) a link showing replacement of a head tube, but the sequence for replacing your down tube will be similar.

To remove the dented downtube without damaging the lugs, first cut the down tube in half. Coat the lugged joints with boric acid flux, then evenly heat the down tube/lug joints one at a time using a big cool oxygen-propane torch. Heat the entire joint evenly so that the tube can be pulled from the lug without damaging the lug.

If the joint is pinned, you'll have to cut the downtube close enough to the lug so you can reach the pin with pliers and pull it out while the joint is being heated.

Thanks man. I probably wont tackle this for another few weeks, but i hope it works.