My headset loosened during my ride today

[Vientomas]

Use a steerer tube cutter to cut the shim to a lenght a wee bit shorther than the stem stack height and then file/sand the rough edges off. I've done this before and it works perfectly.

[Pierre]

Originally Posted by marciero

By all means it makes sense to have the shim out of the "bearing pre-load path" as MarkMcM suggests. Having shim completely covered by the stem accomplishes that. The best setup would be a 1" stem and no shim and 1" spacers. Next best I think is 1 1/8 stem covering shim and 1" spacers. I think that having 1 1/8 spacers that clear the shim is the least desirable. The shim would have to pass through only part of the lowest and highest spacer (at least the lowest) in order to have them both centered and not loaded. Plus you would have mismatch at the headset. I remember having 1" threadless stems back in the day...

Agree with this!