Originally Posted by
rsterman
That makes me assume the Pivo stem bar clamp must be at least 25.5 or 26 mm. Is that a wrong assumption on my part?
Yes, it's a wrong assumption.
While you might be able to force the stem apart enough to jam a 26.0 handlebar in there, it is likely to fail eventually. Don't do it. You've already been warned that these old french cast stems are prone to disastrous failure. Having your handlebars fall off while you're riding is not something to take a chance on.