... AND, PASS THE AMMUNITION ...
As noted, YOU CANNOT SLEEVE A 1.125" STEM OVER THE CURRENT 1.25" STEERER ...
Regardless, your current dilemma is not without a fairly easy resolution ...
It
only requires that you are moderately handy + that you are willing to undertake a fairly simple DIY project ...
GIVEN that your current fork's steerer is probably a "hollow" carbon fiber tube ...
Presuming that you are comfortable with your bike's current setup as far as handlebar height & reach AND your new Cinelli bars would theoretically replicate the position if you could mount it, then YOU simply need to replace the upper portion of teh steerer which is equal to the height of your current stem ..
So, YOU only need to be able to measure the
inner diameter (ID) of your current steerer ...
In a "perfect world" it will be 31.8mm (1 1/8") ... you can probably get a 10" piece "scrap" (alloy) steerer from your LBS ... worst case scenario, you can probably buy 1 1/8" OD steel pipe from a plumbing supply store ...
The minimum size of the steerer's ID which you can work with is a minuscule 22.2mm.
And then, replace a portion with a length of 1 1/8" (
"salvaged" from the installation of a standard fork) steerer ...
I would probably want the inserted tube to extend an inch below the upper headset bearings ...
I would definitely want at least 2cm of the current steerer to extend above the headset.
- measure the ID of the steerer
- procure ~10" length of 1 1/8" tubing
- measure the height of the new stem
- if you are happy with your bike's current setup, then that is the amount of the current steerer which you will be removing-and-replacing
- if the steerer has an expansion nut, then tap out through the bottom of the steerer
- OR, if it is a "cap" which was epoxied in, it will already be gone when you remove the excess steerer (put it in your tool box now that you know that you never know when you will want a salvaged part to use)
- mark the steerer at a distance from its top to the length you measured for your new stem's height
- wrap a piece of masking tape around measurement below the mark
- use a hacksaw with a fine tooth blade to remove the excess steerer
- debur with a half-round file or some fine sandpaper
- clean out & dry
- Dry fit the new tubing ...
- if it is too loose, figure out how much you will need to shim it*
- if it is "just right" then (again, AFTER cleaning and drying all the contact surfaces) you will want to apply a thin coat of JB WELD (accept NO SUBSTITUTES) to the inside of the interior of the old steerer and to the portion of the tube to be inserted into the new steerer.
- BTW. I would probably wrap tape around the inserted tube where I want it to protrude to ensure that it isn't accidentally pushed down while the epoxy is curing.
- Set aside ...
- Let cure ...
- AFTER ~24hrs, remove the tape & re-install the spacers & stem
- Adjust and tighten
- Install levers & housing & cables
- Wrap handlebars with tape
- DONE!
* After you measure the inner diameter, let me know what it is.
If you have ANY questions, feel free to ask.