might be combination of vibrations and corrosion... still you wouldn't expect this kind of damage though..:icon_frown:

the only way to fix that is to cut the area out and replace it with new metal
what metal that is left is now so thin that it will crack in time and the steering head area is quite highly stressed...

you need to cut far enough back to find good steel to weld to or the welds will be porus and weak...

i know cutting it out and reshaping a peice of metal to fit is bit of a mauger
job and even more so if you don't have the gear or skills...
but really it is the only way for a safe long lasting fix that you won't have to revisit at a later stage...

something to take into account is the heat and stress you will be putting in a small area on one side
it could pull the steering head towards the side of the patch..
weld in short runs letting the area cool between welds to try and keep the heat build up to a minimin...


Peter