Wobbly headset

[Hillybilly]

Hi. I changed the stem on my bike too a slightly shorter one. In the process I stupidly moved the bike and all the bits went flying off round the garage. Put it back together and the headset would barely move, thought I put the top bit in the wrong way round so turned it upside down the fit looked better but it wobbles under braking. Of course there is the chance that there is a bit sat on the floor of the garage somewhere but visually the spacers look the same height. The brochure says the headset is FSA No.42/ACB BALL TYPE, any instructions on how to fit. Etc

 

[Sharky]

Try putting the original stem back on. If the problem disappears, then there is some slight size difference between the two stems. If the problem remains, then there is either a bit still on the garage floor or something amiss in the refit process. If research on You Tube doesn't help, then a trip to the LBS is probably the best. Safe steering is a bit crucial.

Good luck.

 

[Jody]

Is the stem the same height as the old one. Take the top cap off without undoing the stem bolts and see how much steerer is showing in the stem. You should have at least 3-4mm below the stem.

 

[youngoldbloke]

As above ^^^
*Stack height of stems varies and it may be that if the new one is not as tall as the old that the few mm difference between the top of the steerer and the top of the stem that allows you to preload the headset bearings has been lost. A 2 or 3mm spacer on top of the stem is usually all that is needed.
*Stack height is the actual length of the stem that slides down onto the steerer.

 

[Hillybilly]

Hmm. Not at home at the moment. But when I did a quick visual check there was what looked like a difference in height, maybe 2mm. having done some reading I understand the idea of how it works now. I shall put the old one back on if that works I'll get the shop to measure up some spacers, if not the shop can let me know what I lost lol. Indeed I don't fancy that oh poop moment. I'll shall post later. Thanks for the pointers.

 

[accountantpete]

Here's an exploded view