I crashed my old DeRosa from the mid-80s, built with SLX tubes. I hit a curb. Front triangle is toast. Top tube lug ripped right through at the tube junction! Amazingly, the fork is OK- minimal straightening required. Now that all my bones are mostly healed, I'm putting a new front triangle on. I brazed on the top tube yesterday. There are no pins in these DeRosas by the way.
I have a Columbus Neuron 28.6 mm tube that I am going to use to replace the down tube. There is almost nothing on the internet about these Neuron tubes. They have elliptical butting. I'm not sure, but I think they might also have asymmetric differential butting where where one side of the butt is longer than the other side of the same butt (like Nemo tubes).
The tube has a small tab on one end, located on the inside of the 0.9 mm part of the butt. The butt is 0.9 mm on the thicker part and 0.7 mm on the thinner part of the butt. Does anyone know rest of the anatomy of the butts in these Neuron tubes? Are the butts on both ends the same length? Are the butts asymmetric and, if so, how does the tab tell the orientation of the asymmetric butts? Which way should they go in?
Thanks, Mark Walberg