Steerer "Lengthening"

[danson67]

I think that as long as the actual steerer extends above the top of the headset, the extender is built heavy enough to take the forces from the stem.
In effect, the arrangement is structurally much the same as a quill stem in a threaded headset.

I'd be wary of extenders that use wedges, ideally they are 360° expanders to get better contact with the steerer.

This is one of the better ones that I've seen: https://www.ebay.co.uk/itm/303954023499, in that it has a deep knurled expanding section to grip the steerer, and also (I think) compresses the headset correctly via that flanged spacer at the bottom. The stem then just clamps on.


If you do use one of the more conventional extenders, the top cap can usually be swapped out for a larger diameter so that it compresses the headset as it's tightened.


Alternatively, there are expanding headset spacers available. With these, you fit the stem pressed down as much as you can by hand, clamp it up and then vertically expand the spacer to load the headset. https://problemsolversbike.com/products/headset/adjustable_spacer_-_6547



All the best.

 

[pazaudi]

Thank you all for your help, it's nice to know I now have an option in the near future when I get around to making a start on my build.

 

[The History Man]

Thanks also.

 

[velomaniac]

Came across something similar. Taking a headset apart on an old bike I discovered the the headset was threadless when I removed a plastic cover on top of stem. There was no star nut or expanding wedge adaptor for Ahead stems. I think what had happened was the headset was compressed in a workshop to the required amount with a headset press then locked off with the stem bolts thus not needing a star nut for later adjustments.
My bodge is this, use a 28.6mm seat clamp instead of a stem to lock the steerer in place once the required compression is achieved with a headset press. Do not fit a star nut so you can use a threaded steerer extender or quill stem.