from Chim-Chim:
I may have a fix for the broken kingpin problem. I have found two reasons that support
the cracking on these pins. The first one is that there is some play on the wheel hub
adapter.(pull your wheel forward and back while holding the lower arm). This play allows
the wheel to move lateraly putting excess stress on the lower kingpin(try this and look
at the lower kingpin while you move the wheel, it rocks back and forth on the hub, cracking the pins.)
A narrow shim between the bearing and hub adapter should help remedy the problem. Another thing you can try
is grinding out the narrow bridge that the pin rides on, increasing the surface area inside the hub. What do you guys
think, let me know.