Joined: Aug 2010
Posts: 12,749
Likes: 2,111
From: Madison, WI
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
I am largely clueless on this sort of thing, so I default to Garmin instructions or specifications which usually specify no more than 32gb.
I suspect that there is a different formatting system or something like that for different card sizes. I tried a 64gb micro SD in a camera and the camera was not happy with that.