80k with a bike computer-- on a fully loaded tour down the =west coast, somewhere in California I think, long downhill with a tailwind, very stable and with tailwind was very uneventful and quiet.
a few years earlier, before i had a speedo, I am certain I went faster on another loaded trip around the Gaspe penninsula--prob 90k or more, as my legs were shaking at the bottom from the experience--I had raced motorcycles circuit racing so was used to speed, but that descent gave me the shakies....
hit 70k on the new cross bike last week down the steepest hill here in Montreal, on Mont Royal.
50x11 means I can spin up to about that, my touring bike 50x13 would run out of gears at about 55k.