My headset loosened during my ride today

[mktng]

check your start nut.

[Jaybee]

Originally Posted by ANAO

Did the lack of total flushness give you issues other than the obvious aesthetic ones?

When I finally took it out, it was pretty gritty inside, especially for a bike that only saw dry road miles. So I assume I would have gone through bearings pretty frequently. It didn't feel gritty while it was on there though.

[Mark McM]

Originally Posted by ANAO

The question then becomes: will this happen to me every X times I ride my bike? If so, I should just swap out to a 1" spacer. The problem with that being that the deda stem has about a 37mm stack height and the thomson shim is about 42mm, leaving roughly 5mm that would be exposed between spacers. Which would be fine, I guess, except ugly.

The spacers are stem are generally manufactured to have parallel faces, so as to provide a uniform bearing pre-load. The shim? Who knows.

How thick is the 1 1/8" spacer? If the shim is 42mm, then the combined height of the stem plus 1 1/8" spacers needs to be greater than 42 mm. That will ensure that the bearing preload passes only through the stem and spacers, and not through the shim. Perhaps add an extra 1 1/8" spacer above the stem (and make sure the shim doesn't press vertically on any spacers).

[seanile]

Originally Posted by mktng

check your start nut.

yea. when you tighten the top cap, you may be pulling the star nut up the steerer and not actually tightening anything

[ANAO]

Originally Posted by seanile

yea. when you tighten the top cap, you may be pulling the star nut up the steerer and not actually tightening anything

This is not the case.

[johnniecakes]

Did you check to be sure that when you tighten everything up that the split in the adapter is not fully compressed? If it is them the inside of the adapter is not in full contact with the steerer tube.

When you figure what went wrong and before you finalize your assembly give both the inside and outside of the adapter a generous coat of carbon paste before you torque the stem to prevent it from happening.

[Pierre]

Sorry if this was already covered but are you certain that your steerer tube is in fact SHORTER than the sum of spacers and stem?

If its flush or almost flush with the top, no amount of tightening is going to get the correct pre-load on the cups/spacer/stem.

[Pierre]

Originally Posted by Mark McM

The spacers are stem are generally manufactured to have parallel faces, so as to provide a uniform bearing pre-load. The shim? Who knows.

How thick is the 1 1/8" spacer? If the shim is 42mm, then the combined height of the stem plus 1 1/8" spacers needs to be greater than 42 mm. That will ensure that the bearing preload passes only through the stem and spacers, and not through the shim. Perhaps add an extra 1 1/8" spacer above the stem (and make sure the shim doesn't press vertically on any spacers).

Meh, I've got a 1" set-up on mine and my shim is completely covered by the stem. This allows me to continue to use 1" spacers above and below the stem if/where necessary. This also means I've got a 1" cap. I guess there is nothing wrong with using a 1 to 1 1/8 sleeve all the way up but you'd need to cut it correctly to make sure you cover the whole height above and below...seems like a pain in the a$$ to me.

[ANAO]

Originally Posted by Pierre

Sorry if this was already covered but are you certain that your steerer tube is in fact SHORTER than the sum of spacers and stem?

If its flush or almost flush with the top, no amount of tightening is going to get the correct pre-load on the cups/spacer/stem.

The steerer is short enough.

[Steve in SLO]

Thinking about the other end of the steerer, is it possible your crown race was not seated all the way, and after some ridng, it migrated downward, seated itself and left a gap in the spacers?

[ANAO]

Originally Posted by Steve in SLO

Thinking about the other end of the steerer, is it possible your crown race was not seated all the way, and after some ridng, it migrated downward, seated itself and left a gap in the spacers?

Hmm possibly but I rode this fork a number of years ago on a different bike and never had an issue with thayt.

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[mktng]

Get another shim.



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[ultraman6970]

Maybe the top and the bottom contact surface of the stem is not straight and thats what is causing the problem. Put carbon fiber paste to the expander aswell.

[charliedid]

How square is the steerer tube cut? If not square the starnut may not be seated straight and in turn everything shifts.

Also why not just buy a correct size 1" stem and forgo the shim deal?

[marciero]

Originally Posted by Pierre

Meh, I've got a 1" set-up on mine and my shim is completely covered by the stem. This allows me to continue to use 1" spacers above and below the stem if/where necessary. This also means I've got a 1" cap. I guess there is nothing wrong with using a 1 to 1 1/8 sleeve all the way up but you'd need to cut it correctly to make sure you cover the whole height above and below...seems like a pain in the a$$ to me.

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...