Originally Posted by
cajunpedaler
What are the pros and cons of bigger or thicker or smaller diameters in handlebars and matching diameter stems?
All other properties being equal, larger diameter tubes are stiffer, which would be a pro.
31.8 mm is the current standard for road bars, or at least it has been for the last two decades or so. The adoption of 31.8 mm handlebars coincides with threadless stems.
25.0 (French), 25.4, 26.0, and 26.4 (Cinelli) are past standards, typically used with quill stems.
Originally Posted by
ksryder
Pros - 31.8 has removable face plates on the stem making handlebar and stem swaps/adjustments easier (you don't have to unwrap the bar tape and remove the shifters every time you want to change stems.)
Since 31.8 mm bars and threadless came into general use at the same time, and threadless stems typically have removable faceplates, it is generally true that stems for 31.8 mm bars have removable faceplates.
BUT... Removable faceplates aren't unique to 31.8 mm handlebars. There are/were stems for 25.x and 26.x mm bars that also had removable faceplates. Both quill and threadless.