In order to install a new set of maps on my garmin edge 520, I downloaded from site "http://garmin.openstreetmap.nl/" the file "gmapsupp.img" 85mb, renamed it as gmapbmap.img deleted the existing file "gmapbmap.img" 45mb and tried to copy the new "gmapbmap.img" file but received the message "not enough space". The site, for that case, recomended that I should not only delete the old file but also "empty the trush" from Garmin device I suppose. Where is that "trush" in my garmin?
Are you sure you have enough free space on the Garmin for a 85 MB file, even after removing the old map file? The Edge 520 has very limited storage of around 100 MB. That is also used by the stored activities, which can take dozens of megabytes if you never remove them.
I have used a 88.5 MB map loaded from the same site on my Edge 520, but I had to remove the activities from the device every couple of months. The device doesn't warn you when low on storage space, so you find out when it finally fails to store your whole ride.