Mix and match Headset

Luke

Swapping out forks on my Schwinn I discovered when removing the HS
crown race of the old forks that it had been shimmed to provide a snug
fit. (Considerate of my LBS to tell me this when they installed their
HS.) A caliper reveals that the YST's crown race is 27mm while both
the original and replacement forks have 26.4mm crown race seats. The
shim itself appears to improvised from a beer can. Looks like Stella
Artois. Good taste!

Though I wasn't pleased to discover the arrangement, I confess the
crown race fit was quite secure; it took effort to remove and obviously
was pressed on with force. As it should be. Looks like the LBS wrench
was familiar with the procedure.

The headset is a threadless 1 inch YST HP250A. It has ball bearings in
the upper cup and rollers in the lower. I didn't want to utilize the
shimmed crown race setup with the new forks - partially because I
really don't know how to press fit the shim/race combination onto the
seat without mangling the delicate shim.

So I reached into the parts box. There I had an old FSA Duron 1"
threaded HS - also of an upper ball/lower roller configuration. The FSA
employs a split collar that slides over the fork crown race seat. No
press required. Two conical sleeves act as races and sandwich the
roller bearing cage with the lower race sitting atop the split collar.

It mimics the setup of the YST HS, with the exception that the YST's
collar (previously referred to as crown race) is not split. But despite
the collar being press fit onto a fork's crown race seat, it also forms
the base of a conical race/ roller bearing sandwich like the FSA. (ie
the rollers' lower conical race rests directly atop it.)

Another point: Since the FSA employs a split collar I'm unsure whether
it's specifically designed for a 26.4mm crown race seat (it initially
was installed on such), a 27mm seat or both.

I initially contemplated replacing the lower cup assembly of the YST HS
with that of the FSA. Aesthetically, it's not an issue that the HS
employs cups of different makes. But I do want the result to be
mechanically sound.

But, first I thought to try this: Installing the FSA's split collar and
using it conjunction with the YST's lower bearing cup assembly - sans
it's own press fit collar. I reassembled the bike and set the HS
preload. The bearings aren't binding, the forks turn freely and there's
no play in the HS. But this isn't exactly a rigorous test of the
soundness of the proposition.

I haven't gone for an extended ride yet. Any comments before I do.

Thank you
Luke