Alpinestars stem - what sorcery is this?

I think it’s t’other way round, he has the stem and he wants to use it on some normal forks.

But if you can measure the forks that will answer the original question !
 
Ah... didn't read it properly. I would measure the forks but sold them about 2 years back. Still the pic of the forks might provide a clue.
 
Is it these forks you have. These were from a 92 Al-Mega.

View attachment 590177

Thank you for that pic. I think that is the first time I have seen the top of a steerer that these stems were made for. 29.8mm seems to be a tandem seatpost thing and there are stoker stems made by Controltech and others with this bore, at the steerer end. I understand a little more now why they went down this route and how it all worked with the top of the steerer. I have a regular 1 1/8th" steerer tube and now I have one of the SJS shims on its way to me, to make the stem fit. Hopefully it will be just the ticket and the bars will be exactly where I want them.

Thank you all for pics and info. It has been interesting.
 
They were specific, I had an alpinestars fork once, unnatural thing it was, as pointed out 1¼" threaded headset but awkward sized ahead stem, not sure if I used a shim on a 1¼" aheadstem or cut the threaded part off and used a 1" quill that fitted perfectly in the end.

No help at all..... Soz
 
To anyone who may be interested i can confirm that the 29.8-28.6 tandem seatpost shim as sold by SJS works a treat if you ever want to put one of these crazy stems on a regular 1 1/8th" steerer. Regular top caps with 31.8-32mm outer diameter get enough purchase to pull the stem down, too.
A 25.4-28.6mm stem shim, split in half, works a treat at the bar end of the stem for drop bars with a 25.4mm clamping diameter and with some teasing a 26mm will fit in there, too. All depends on the combination of the tolerances of parts involved, with the latter, so YMMV.

Handy having the larger bore at the bar end of the stem as you can wiggle bars through it without scoring the bars to bits. Have tried an SR road champion randoneur bend and a Soma Highway One compact with success.

Happy crimbo!
 
Is this the 28.6 aka 1/14 one and a quarter sized stem? I seem to have one on a cannondale and would like to reel in the bars a bit as sjs are out of decent human arm extenders
 

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