I've found that while wearing some shoes my foot slips off the ISCI shifter. This does not happen with my leather boots, but the other day I rode with my tennies on and found my foot slipped off easily when up-shifting. If you have this problem you know what I mean.
I slipped three rubber o-rings (size 115) on the groves in the shifter. Problem solved.
I slipped three rubber o-rings (size 115) on the groves in the shifter. Problem solved.