Top Tube Rust
dhowes via our Forum
If the rust has come through the tube from the inside, you will be able to poke an object such as a small screwdriver through it and make a hole, in which case you need a new top tube at the very least. More likely is that perspiration has dripped onto the tube and has penetrated thin paint, starting rust pockets where it has done so. Coating with WD40, as noted, may protect temporarily, but a re-spray will do the job properly although you may be content simply to remove the existing paint and re-paint by hand.
Richard Hallett, Cycle Technical Editor
This was first published in the August / September 2015 edition of Cycling UK's Cycle magazine.