Originally Posted by
bigbenaugust
You will want a chainring with tall teeth, possibly a bash guard, and also a Chain Watcher or similar to keep the chain from throwing. I have also been told that short-cage road derailleurs are better than mountain ones for this.
+1 on the chainring items. Chainring doesn't need ramps for shifting, so something made for the FG/SS market will work. Short-cage derailleur makes sense, you are covering a smaller range (23t for 11-34 cassette) than the design spec for,say, a Shimano SS cage RD (27t).
I've done the reverse, converting a 1x9 (Bianchi Castro Valley frame) to a 2x9 (using old parts from my road bike). Needed a clamp-on braze-on derailleur mount to use my braze-on derailleur, and had to kludge a cable stop on the lower seat tube for the front derailleur cable and secure housing along the full length of the down tube. If unsuccessful, I would have set up a 42 or 39t single chainring with bashguard and chain fang.