On Aug 25, 2009, at 9:40 AM, Steve Maas wrote:
> By the way, an old-time bike mechanic once told me that a common point
> for frame cracking is in the down tube, under the head lug, especially
> if the lug is pointed. That focuses forces at that point and it
> eventually fatigues. Most frames I've seen have the underside of this
> lug rounded, perhaps for that reason.
>
> Steve Maas
>
Correct. Tony Oliver's book has pictures of this very failure. Shifter bosses can also cause this type of failure, especially if they're brazed into the thin part of the tube. I round the points of the boss for that reason. Phil Brown Thankfully none of my frames have failed in Oakland, Calif.