Originally Posted by
Sjtaylor
...Yes, I cold set the dropouts to 135mm...
Whenever you spread the rear dropouts, it causes the derailleur hanger to splay, so that a mounted rear derailleur is no longer aligned properly with the cassette and chain run, which can diminish gear shifting. If you haven't done it already, a LBS with a derailleur hanger alignment tool can can check alignment and fix if needed. The tool uses the rear rim as an alignment reference, so it helps to have a nice true rear wheel for the procedure.