Carbonda fork vibration

[jannmayer]

I've been having some vibrations on the fork of my Carbonda 707 gravel bike. Some times when I am riding on a bumpy surface and braking lightly, the fork will start to vibrate, like a shudder almost. I can't get it to happen on smooth surfaces, and it seems worse if I have less weight on the front wheel. The headset appears tight. I squeezed the front brake and rocked the bike back and forth and couldn't feel anything loose. The hub seems fine. I didn't check the brake rotor to make sure it's tight, but it doesn't feel or sound like that was an issue. The brakes are GRX with Shimano resin pads and Shimano rotors.


Does this indicate a problem with the fork? Or am I just somehow exciting its natural frequency in some conditions?

[FullCarbonAlchemist]

If the headset seems otherwise tight, maybe double check the carbon plug?

I forget, are you using the OEM headset? ACR cable routing?

[jannmayer]

I am using the factory headset and plug, no ACR routing. I will check the headset tonight if I have time

[jannmayer]

I reinstalled the carbon plug. The top bolt wasn't very tight, so maybe that was the issue. It felt more like the fork flexing than a loose headset though.

[FullCarbonAlchemist]

Carbon plugs are always tricky in my experience. They have to be checked, tightened and even re-settled pretty often.

This (plus ease of trimming the steerer tube, higher stack height and 15mm axle compatibility) is a big part of why I’m trying a suspension fork on my initial 707 build rather than the OEM carbon fork. After carbon plug issues cropped up several times with my fat bike when it had a carbon fork I just like the peace of mind of a star nut system.

I also use FSA headsets instead of the Carbonda OEM ones because I’ve had some creaking and slight knocking/play develop in the one that came with my FM1002. Swapping out for an FSA no.55R-558 (no cable routing) solved that immediately. At some point if you’re still feeling shudder despite the plug being tight, you may want to consider that upgrade before looking at a different fork.

[carbonazza]

You also need to check the space between the top of the steering tube and the plug. Sometimes the tube is cut too long, which makes it contact the plug, preventing proper compression.

Keep tightening the plug gradually. Place the bike on the ground, pull the front brake, and place your thumb and index finger in front and back of the frame where the headset contacts. Then, push/pull the bike to feel for any play. Tighten the plug just enough so you don't feel any play, but not too much more than that.

[jannmayer]

Thanks for the suggestions. I tightened it last night and will give it a test ride this weekend.

[PLA]

perhaps a rotor with some warping. i've had this before.

[TidyDinosaur]

I had the same problem with my Carbonda 696. I checked the fork just now, but there was no play in the bottom bearing area. BUT: then I noticed there was play in the upper bearing area.
I tried upping the preload with the top cap bolt, but could not get it tight enough. It looks like the expander was the problem. The spikes on the surface of the expander seem to have become dull, so there was not enough grip and I just pulled the expander up instead of increasing the preload.
I had another expander, put that in the fork tube et voila. I can not get enough preload to stop the movement.

[mcs5280]

I moved to the 50mm long Origin8 alloy compression plug and it solved the slipping issues on my 696 fork

[PLA]

I always compress my headset with a quick clamp. Some can be tricky to get down if the brake hoses are particularly stiff.

[jannmayer]

I've put about 20 miles on it since tightening the top cap bolt and it feels solid now. I have an Origin8 expansion plug and will be replacing the Carbonda plug. Hopefully that keeps it solid.