What considerations should be made for converting a downstem shifting system to barcons? Both the current system and the system that I would like are friction shifters.
The bike is a 1986 Peugeot Iseran 10-speed.
Thanks and be well.
If they are both friction shift sets, there is no conversion necessary. Just new cables, and placing the new shifters on the bar before routing the new cables.
Difficulty might be finding good quality friction shifters to begin with, but there's nothing complicated about the changeover.
According to the '86 Peugeot catalog you're dealing with stem shifters. You should have cable stops on the downtube. You will use those. Measure your handlebar inside diameter to ensure you can find barcons that will fit. If it's not standardized, get a new handlebar.