i have the 500 in front of me and you do have separate odometers.

if you go to menu, settings, bike settings, bike 1 (or 2 or 3), bike details, it shows you the bike info including odometer. you have to go to this menu every time you switch bikes so it keeps track appropriately.

you can even set the starting odometer if you're switching from another computer. for instance, when i purchased the 500, i already had 800 km on another computer. i entered 800 into the 500 and it kept track from there.

now i'm trying to figure out how to get garmin connect to separate out my bike 1/bike 2 rides.

j