Originally Posted by
Andrew R Stewart
Ovalization of headtubes when the tires really don't leave the ground (as in jumps) is a very uncommon thing. Using a gap filling LockTite compound isn't wrong if the tube isn't ovalized, But might make removal of the headset a real challenge later on. Ovalization is far down the list I would be checking off. Andy
Ovalizing of the bottom of a head tube is not particularly common but not unheard of, especially for 1" headtubes of bikes ridden at speed (happened to one of my bikes after a couple of years of East Coast singletrack, which is much rougher on bikes than smooth fire trails). In any event, the OP says that this sounds like the correct explanation.
To the OP: I used Loctite bearing retaining compound, which is way up there in strength among their adhesives. I pulled the stem out, used a head tube cup removal tool to pop out the bottom cup (or maybe it just fell out because of the ovalizing; I did the repair about 30 years ago, so I don't remember), painted the cup with enough compound to fill the ovalized gap, and used a headset installation tool to clamp the top and bottom cups in place. I think I left the glue to dry for about 24 hours before I reassembled the bike.