am bumping this up..'cause I'm certain some folks living not far, would have done this island ages ago. I've been told it is flatter....at least compared to several Canadian Gulf Islands. It looks like 60 kms. circuit around the island.
We are planning our trip in such a way, that lst day leave home 4:30 am to cycle to ferry dock. (That might include 1 segment with bikes on bus for a short piece), then drop stuff off at hotel on Vancouver island before ferrying to Saltspring Island for cycling day. Day probably will be 80-90 kms.
2nd day cycle, short ferry to cowichan valley on Vancouver Island for winery, lovely luncheon, come back and catch ferry to Friday Harbour, USA. That day will probably be 65 kms. I'm not clear.