Originally Posted by
Grand Bois
The "demultiplicator doohickey" will make it pull less cable. Maybe Suntour RDs are a bad match with those shifters.
Yes, the Simplex retrofriction downtube levers have a smaller diameter barrel than SunTour shifters (14.2mm vs. 20.9mm) and thus will pull less cable. Since barends are already limited to about 90° of travel (downtube levers can travel nearly 180°), the smaller barrel may not work in the barend pod for a derailleur expecting more cable pull.