Originally Posted by
thook
HMMMMM!!!! I may have found it......
https://www.xxcycle.com/stem-humpert...211-mm,,en.php
It'd be quite similar/reminiscent of the original Ross stem with the steel insert and black alloy extension. Still open to other options anyone may know of. Again, something like the Promax above would be great if there's taller ones?
Being unfamiliar with MTB and BMX stems and forks from that era, what's the outside diameter of the steerers that take a 21.1mm / .830" stem?
Easiest way to tell is what's the thread size of the headsets?
If it's 1", the steerer can be bored out to 22.2mm on a mill or a lathe. Trying to ream out 1.1mm is a LOT of work. Reamers are intended to remove a much smaller amount of material to accurately size a bore.
The fork would need to be rigidly fixtured on either a mill or lathe while boring it out, otherwise the cutting tool can easily grab inside the bore and you have a mess! (Been there - done that).
Several other things: the bore should have a taper at the bottom of the resized area rather than a sharp shoulder to reduce the possibility of a stress riser and... make sure that the expander wedge is below the threaded area of the steerer. 75mm to 80mm is the recommended minimum amount of insertion for the stem into the steerer.
There are a number of European websites that list the Humbert Dino-X 21.1mm / .830" Stems pictured above. They all appear to be out of stock except for maybe xxcycle and the info goes back to 2019.
I wonder how strong the cast aluminum extensions attached to the steel quills are on those Humbert Dino-X stems. Probably OK for around town use but I wouldn't feel comfortable with an average sized or larger adult using one of those off road.
Also, I wouldn't recommend removing 1.1mm+ off of the diameter of a 22.2mm aluminum stem like those tall boys from Nitto. The wall thickness of the quill would probably end up being too thin.
Here's a suggestion: get an old steel 21.1mm MTB stem with a brake cable roller that you like and have an extension TIG welded to the bottom of the quill???
Back in 1991 I built this lugged Reynolds 531, 700c off road trekking frame. I had some neck problems and Salsa made me this short reach, high rise stem. Solved a bunch of problems!
One last thing, I just saw these Cro Mo steel stem extensions. Dirt cheap!
https://www.ebay.com/itm/153723416080
verktyg
