One you're pretty certain that the bar and stem in question *should* go together (i.e., that they're compatible diameters), you can proceed. It seems to me like you're Ok, here...both the stem and bar should be 26.4mm dismeter.
After that, you might want to measure things and eyeball matters and see if there's an obvious reason why they're not fitting (e.g., the stem could have evidence of having been tightened down on a 26.0mm or 25.4mm bar or some such).
Lacking any good reason why it's not working (and this has happened to me many a time), it's time for encouragement. The wood shim method has worked for me sometimes, but the sure way to do it is to carefully force the ears apart with a fastener. Do be careful, you don't want to use this method any more than absolutely necessary -- stems aren't very flexible, and it's easy to break the clamp if you don't pay attention.
So, get yourself an M6 nut and bolt, and a long-ish metal object with a divot in one end (a baby spoon works nicely if you don't get caught). Put the bolt into the clamp-bolt hole in the stem...halfway...and put the nut on it *between* the two ears of the clamp (I have a thin not I use for this, it makes the clearances easier). Now, run the bolt in a little further and use the bowl of the baby spoon (or a piece of 1/2" x 1/8" x 4" aluminum bar with a small divot near one end (from, say, starting to make a hole with a large drill bit)) to keep the end of the bolt from going on through the second clamp ear. Hold the nut to keep it from turning, and *gently* tighten the bolt. The end of the bolt will push the two ears apart. You have leverage now...easy enough to push the ears apart (and almost as easy to snap the clamping section, should you be over-eager).
Get the bar in there and use this technique *just* *enough* to get the thick part of the handlebar in without scratching. It's good to have a helper, so that one person's *sole* *duty* is to do the spreading part without hurting things. The inner faces of the two ears aren't quite parallel, so things want to wander and pop out of place (hence, for example, the divot). It really doesn't take much though, once you have this kind of leverage (rampage, I guess). Metal-to-metal contact can be minimized using thin nylon washers and judicious wraps of gaffers tape, if you're paranoid like me.
Remember to get the centering and angular position right before you release the mechanism.
If this is less than clear, feel free to email me and I can take some pictures.
Cheers,
Scott Minneman San Francisco, CA, USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Bill Kloos Sent: Monday, May 10, 2010 7:36 PM To: classicrendezvous@bikelist.org Cc: Bill Kloos Subject: [CR] Installing stem on handlebar without buggering the bar?
Team CR:
I am trying to install a used Cinelli 1A oval logo stem on a new bar - an
"Ambrosio 13 Volte Champione del Mondo." The Velobase picture of the bar is
here:
http://www.velobase.com/
I can get the stem up to the start of the wider part in the middle of the bar, but it is clear to me that I am going to bugger up the bar if I keep pressing the stem toward the middle, where it has to go. I have put a wooden wedge into the opening on the stem (the kind you use to straighten up a door frame), and this has given me bit bigger opening, but it will not be enough.
What am I not doing here that should be obvious to me. I really don't want to mar the bar, as I will lose sleep. Should I use a hardwood wedge? Should I bathe the bar in liquid nitrogen and heat the stem? I actually searched the archives and found nothing, so I fear I am missing something really basic. But there are not many variables left.
Thanks.
Bill Kloos Eugene, Oregon "Last refuge of the terminally hip."