Originally Posted by FBinNY

No I didn't. Aluminum drop bars typically have a different clamp diameter than straight bars.

Just about every straight bar has a 1" clamp. But only drop bars from Japan or Taiwan use that size. The more common drop bar clamp br clamp diameter is 26mm and straight bars of that diameter are rare.

Measure your bar's diameter in the bulge area just outside the stem. You don't need a precise measurement, since you're only trying to confirm if it's 1" or larger (the stems brand might also be a guide). If you don't have a caliper make a gauge by cutting a dovetail shaped notch in a piece of cardboard, then carefully cutting the open to exactly 1" as measured on a ruler. You should end up with a sort of "C" cutout which will either just fit over the bar, or be too small.

Odds are you'll need both a bar and stem for the conversion, but you may luck out.