steering, stem, bearings, tapered, notched,
http://www.flickr.com/photos/caffeineracer/
During hard braking the steering stem stretches and the balls roll up the bearing races.
Since the bearing doesn't continue to rotate in the same direction the balls are always in the same position on the race during braking. After a while the ball rolls a groove/dent into the race and your steering can become notched in the straight ahead position. It helps to keep your steering bearings preloaded and to rotate the ball cage to a new wear area when you grease the bearings. But those things didn't help me much, these worn out bearings only have 19,000 miles on them.
This is where tapered bearings come in, they can't roll up the race and have a much larger contact area to spread the load over.
I've never had to replace tapered steering stem bearings.
(the following is to the best of my knowledge, have not recieved bearings yet)
steering stem tapered bearings
Allballs part# 22-1003
same as GSX1300 99-06
~Jeffers