Need another opinion. What am I missing?

Third or fourth ride on new gravel bike. First time off road, and I noticed a bit of a vibration when braking. ‘No problem’ I think to myself. Just need to adjust the headset preload a fraction. Now the problem …

Loosened off stem bolts, but I can’t tighten the top cap bolt sufficiently. The top cap isn’t bottoming out. The expander plug is slipping on the inside of the stem. It’s a carbon steerer tube.

Any ideas or similar experiences? How do I solve this one?

Depends on the design of the expander plug but I assume you’ll just have to push it back down a bit and make it tighter. I had a similar problem with mine and this is all that was required.

I’ve pushed it back down, and torqued it up more than I’d have liked (14Nm), but it’s still the same. Slips every time. Thinking about using glue to give a bit of grip.

How ‘shiny’ surfaced is either the inside of the steerer tube or the surface of the bung? A light rub down of the surfaces with a fine sandpaper might cure the problem

get a bbb expander plug and rub a bit of carbon paste on it. Tighten it up to torque spec and leave it overnight for the paste to dry out and the gripper to bite the steerer. Then fit stem and top cap.

Thanks, I’ll give that a go. The inner surface of the steerer tube hasn’t been roughed up yet. I’ve got some carbon paste too.

try your current expander but I’d not risk anywhere near to 14nm! isn’t 6nm max on carbon steerer?

the bbb expander has a more gnarled surface than other plugs, they’re like millions of little pyramids. Let the paste dry a bit because it may lubricate the plug if it’s wet.

I had loads of problems with the plug on my arkose pulling out so binned it for the bbb.

Are you sure is isn’t one with 2 adjustments? A larger bolt in to expand the plug then the top cap as per a standard star fangled nut one.

I found this after breaking an fsa one due to similar reasons to the above.

one of these

I’ve put in a different expander plug off another bike, which may be the BBB one mentioned.

Will check and give the paste a go.

Enough spacers to lift stem above steerer? Obvious I know.

Aye, there’s enough spacers. I event popped a really big one on there, which allowed me to keep turning the stem bolt and pull the expander bung out further.

I’ve put some carbon assembly paste on and will wait for it dry a bit overnight.

If that doesn’t work I’ll get one of those BBB ones.

Cheers for all the suggestions.

I had an alloy steerer that. ‘Jammed’ up on the top bearing assembly/compression ring. It took some firm rocking back and forth, while tightening up top cap to cinch everything down.

It’s been a week of frustration, but seeing as I have fixed the problem I had, I thought I’d post up the resolution to close out this topic on a happy note.

Top line summary: A good example of a misdiagnosed problem

The reason the expander bolt was slipping was simply because I was tightening the pre-load bolt too much. Effectively pulling the expander bolt out of the steerer tube. I did replace it with the Colnago one, which is 90mm long and offers good support to the tube, but that didn’t make a difference.

So why was the headset still loose and causing juddering when using the front brake? Basically, the headset wasn’t loose. My LBS confirmed that I’d set it up correctly.

So I figured the headset may be damaged. The expander ring didn’t appear to be a snug fit inside the bearing or around the steerer tube. I replaced the headset, but that made no difference either.

Brake callipers and disks were tight, so I couldn’t see a problem there, but I was wrong. The disks are of the wavy variety and the contact surface with the pads varied as the disk rotated. This was exacerbated on the front as I’d used the supplied spacers (5mm) as per Hayes instructions, which was reducing the contact area with the disk further. The pads on the front were worn unevenly, with more pad remaining on the top edge. When I swapped the pads over (front to back) I noticed the rear wheel braking was very juddery too. Fresh pads solved the problem.

It may be sufficient to have removed the spacer, but I’m going to get some round rotors, as once the new pads start to wear I guess the problem will return. Why are rotors wavy anyway?

Happy to have a solution. Less happy that I didn’t diagnose it sooner. Another thing to mark down as a lesson learned and move on 🙂