the lower race set composed of:
fork crown race with the concave side facing up, a bearing race that is pressed onto the fork steering tube--this is the bottom end of the lower bearing race set
ball bearings, usually held together by a retainer (spherical wire contraption that holds bearings together), and which are cupped between the concave surfaces of the fork crown race and the lower bike head tube bearing cup
lower bike head tube bearing cup with the concave side facing down, which is pressed into the bottom of the bike's head tube--this is the top end of the lower bearing race set
the upper race set composed of:
upper bike head tube bearing cup with a concave side facing up, which is pressed into the top of the bike's head tube--this is the bottom end of the upper bearing race set
ball bearings, usually held together by a retainer, and which are cupped between the concave surfaces of the upper bike head tube bearing cup and the top bearing race
top bearing race with a concave side facing down--on a threaded fork it is threaded like a big nut (on a threaded fork this race is also called the "adjustable cup"), but on a non-threaded fork is held in place by a plastic compression ring--this is the top end of the upper bearing race set
on a threaded fork, a lock washer and threaded lock nut, which is threaded onto the fork and presses down against the top bearing race to hold everything in place
on a non-threaded fork, a star nut pressed down into the fork, and a top cap that fits on the top of the fork steering tube--a stem ring holds the top cap onto the star nut, holding everything in place; in addition varying spacers and dust caps
Threadless Headset
Threaded Headset
