Lower headset not sitting flush on crown race

[cogs19]

Hi

I replaced a headset today and all went well until I put the fork in and there was a 1-2 mm gap between the crown race and lower headset cup.

Semi integrated headset.

Both top and bottom cups pressed in fine.

Crown race (which came with headset) installed easily on steerer tube.

I’m at a loss to understand how the crown race and lower bearings don’t mate flush.

Any ideas?

photo https://ibb.co/n4R4xo

[RonK]

There is another recent thread this. The fork had an integrated crown race.

[cogs19]

There is another recent thread this. The fork had an integrated crown race.

I'm not sure that's the issue here. The crown race that came with the headset sits flush on the flat top of my fork at the base of the steerer. The gap is between the crown race and the bearings/cup.

And I removed the crown race that was originally on the fork during the de-install of the original headset.

[Duck!]

Is there a difference between top and bottom cup depths, and a possibility you might have put them in the wrong ends of the head tube?

[cogs19]

Is there a difference between top and bottom cup depths, and a possibility you might have put them in the wrong ends of the head tube?

Good lord I hope not!

Here's the headset - https://bbbcycling.com/en_en/bhp-50-semi-integrated

I'm pretty sure top and bottom cups are identical (9mm depth on both). Anyway I put the top in the top and the bottom in the bottom (99% sure on this) and when I noticed the fork not sitting flush I did remove it and invert it into the top cup to see if it would fit flush in that way (it didn't).

Tomorrow I will pull it apart again and see if the crown race when it's not on the fork fits snugly into the bearing cup or not.