Hi, this is my first try at installing a sealed-bearing headset. Model is FSA Orbit MX 1-1/8 threadless.

when I dry fit the bottom part, there is a gap at the top of the fork race, maybe a couple mm, but it doesn’t look right.

if I take out the little metal collar, the gap tightens a bit but the action isn’t as smooth. So that doesn’t seem right either.

Any thoughts?

Take what I say with caution -- I just installed my first headset a couple days ago.

And the first thing I learned about picking parts is that there are (of course!) two standards for the diameter of the collar that the crown race is pressed on -- 26.4 mm and 27.0 mm. Because that's how we do in the bicycle wold (*).

Grab a caliper and measure. On my 87 Cannondale steel fork, the collar measured to 26.44 or 26.45 mm -- IOW about 50 microns larger than advertised -- which is probably what is required to make the press fit work.

The origin8 headset I bought happily came with two crown races, one for each standard. The 27.0 rattled more than I would have guessed when slipped on the collar, and the 26.4 "wanted" to go on but was never going to go with just hand strength. There was no confusing the two. Maybe your fork is a 27 the race a 26.4?

I would agree with you that it doesn't look right.

Good luck!
cheers -mathias

(*) Take for instance, older handlebar clamp diameters, which are 25.4 and 26.0 mm. At least you know there's no engineering reason behind the sizes when they're so close. This kinda stuff drives me nuts.

Would this help?

https://www.bikesdirect.com/products/...sa_headset.pdf

That only applies to 1" headsets which come in two sizes, JIS (27.0 mm crown race) and ISO (26.4mm crown race). The OP has a 1-1/8" headset and they are all the same diameter.

Also, the crown race (or base plate in the case of a cartridge bearing headset) is usually a firm drive fit and will not seat fully without some force. There are specific tools, basically slide hammers, used to drive them fully into place. A few models of headsets come with split crown races/base plates that can be fully seated by hand. Velo Orange's Gran Cru headset is one that does. Most others require tools.

From your photos it looks like you're trying to install the new crown race over an old one.

Looks that way to me as well. Your fork already has a crown race installed . It would have to be removed so that you can properly install the crown race that was provided with your new headset

You appear to have one too many parts. I suspect that the part that the red arrow points to in the picture below was on the fork when you took it off the bike. It’s probably the crown race from the original headset. You need to remove it.



The metal “collar”



The race marked with the yellow arrow shouldn’t be there and the race marked with the red arrow should sit flush on the crown.



If you don’t have a crown race removal tool (most people don’t), you can remove the race with a screw driver (be very careful around the carbon bits!) or (better) get a bearing splitter. You can get them from a bunch of different places and might be able to rent one or borrow one from an auto parts store.

What is the fork from originally, and what spec headset did it have originally? as if you can ID them, and compare to the bearing that the Orbit has, you may be able to just use the original fitted (on the basis that you haven't wrecked it by trying to install over the top.

Got to look at this and think that your way out your depth here, either a case of asking/researching before you cause expensive damage, Park tools site as mentioned, or Youtube for how to videos