Originally Posted by
clubman
I have dated 1951 Reynolds drop bars that are 23.8 and require a shim to fit old GB Hidminium bars. I suspect this was always a thing.
Brass shim stock will work in most any application as will aluminum. I make sure to have any gap or overlap centred in the opening in the stem to prevent stress risers
Yes, that was a pretty common English handlebar standard, as 23.8mm is the metric equivalentt of 15/16". I've seen lots of English bars that used a shim to accommodate the stem. My only shim advice is to to not build up the shim with several pieces of stock. Use a single piece of the correct thickness. The more layers between the bar and stem, the greater the chance of slippage.