str8jakett

Just replaced a headset on a bike I've owned since 2012 but has been on the road for only about four years early on. The new headset was a Giant stock (FSA) bought from Giantbikespares.com and matches all part numbers for this model year TCR. The headset I removed did not exactly match with spacers, and bearing design, but the sizes and overall widths of the bearing/cup washers matched up. I'm getting a bit more gap between the fork and head tube. Replaced all parts with new according to the FSA diagram here:


This is the gap I now have:



Basically I can see the crown race where I couldn't before. But according to the diagram, I have done everything correctly. Double checked inside the head tube and no random parts were left. Measured all the bearings, spacers, compression rings, etc. and all matched what came out. The headset feels smooth and tight, operates as it should. Picture of the top for reference:


What am I missing here?

frankenmike 

Not sure what could cause that gap to increase, but I would just ride it as is. If something didn’t seat thoroughly, it will become evident and can then be easily addressed.

Iride01 

And there is no abnormal play? Straddle the bike on sidewalk or surface that has good tire grip. Lock the front brake and then push forward on the frame, not the handlebars, and then backwards. Does the headtube of the frame move differently than the steerer tube, spacers and other stuff? If so, you need to loosen the stems pinch bolts, then snug down the bolt going to the expanion plug or star nut and then retighten the stem bolts.

Otherwise I agree with frankenmike It'll eventually show you exactly what the issue is. And likely not in the disastrous way you might imagine or even more expensive than anything you might do towards it now.

str8jakett

No play at all and really, it works exactly as I would have expected after replacing a well worn out set of bearings. I'll give it a test ride through the neighborhood before venturing too far away and see if anything changes or seats more properly. Thanks for the advice!

oldbobcat

Did the original headset have seat caps? I replaced the headset on a slightly older TCR, and the bearing seat was an integral part of the frame, so the bearings dropped in without caps. Take another look. If the frame bearing seat isn't beveled, you should use the caps that are designed to drop into a square seat. If they're beveled, the cap won't seat properly.

str8jakett

Good question, but yes the previous headset had seat caps. I matched up the old bearing + seat cap with the new bearing + seat cap to compare the overall height and all had matched.

Rolla

[QUOTE=str8jakett;22609052] The headset I removed did not exactly match with spacers, and bearing design [/QUOTE]

Was the original headset also FSA?

str8jakett

[QUOTE=Rolla;22612218]There was no FSA marking on the headset I removed so I can't say for sure. No size or other markings on the bearings themselves either unless it had worn off. The overall measurements and size were exactly the same one bearings and seat cups were combined, but the seat cups wrapped the internal part of the old bearings more, if that makes any sense. The biggest noticeable difference was the dust cover/top cap that had no markings and was a bit flatter on the old headset and very unlike the FSA top cap that replaced it.

oldbobcat

So the stack heights of the new bearings plus seat caps matches the stack heights of the old bearings plus seat caps, but the new bearings still extend farther out from the head tube. This is weird.

I'm thinking there might be a difference in how the new seat caps are seating. Have you tried using the new bearings with the old seat caps, after making sure bearing bevels match the cap bevels?

str8jakett

Yes, this is what I'm saying, the dimensions are the same.

It is possible the bearings aren't seating tightly. After 35 miles around town and through the park yesterday, I do have some new wobble in the headset, but a lot less than I would have expected. I admit I didn't have any time to inspect or pull things apart to find out if the old seat caps would work after the ride.

Rolla

I wouldn't expect any wobble after a 35 mile ride, if things were copacetic. Something is up with the replacement parts, in spite of the measurements aligning; wish I could direct you towards what to look at; my best guess is the seat caps.

oldbobcat

What Rolla said. Something is wiggling in there that shouldn't be.

str8jakett

I've had no time to deal with this until yesterday. I pulled the headset apart, compared it to the old headset once again just to verify it really did match up with the specifications. The seat cap from the bottom bearing matches and could be swapped between old and new bearings. The old seat cap for the upper bearing is slightly different in design to wrap around the bearing more, but still matches dimensions. I replaced the new bearings and seat caps, added a spacer under the stem, and swapped out the compression plug for one I felt would protect better and have a more typical top cap (cap+bolt rather than cap being tightened to the compression plug). Once everything was back together, the gaps remained, but everything was tight once again. I left it alone as the bike was going back on the trainer anyway. I've got enough maintenance to keep up with on the bikes I actually ride outdoors without adding another into the mix anyway.

Appreciate all of your help and advice on the subject.