Not to be a killjoy but it does not have to be steel. Ask Mark Beaumont or Nicolai Bangsgaard, both RTWers on Koga Alu bikes. I agree steel is easier to weld but in reality, how many frames do these RTWers break? I have read dozens of bike books but have not read where someone has broken a frame. Racks yes, frames no. But I know it does happen, but it must take some effort.