This ride is over.

I think what I should do is take the Zumo XT, a Zumo 550, the Garmin InReach, and a phone running the app and another tracking app and compare distance results between all of them.

GPS tracked 167.5 miles. The App tracked 165.10 miles on the bike and 1.28 walking. 

1.4% discrepancy. 

Then after a stop and restart, it's now 155.34, so there is clearly a bug. 

Yermo is home safe.

This ride is now underway.

GPS 82.7 All 81.4

Gas stop 172.2 miles 3.881 gallons = 44.37 mpg

buffalo is going on K Bike (2009 BMW K1300S).

Yermo is going on The Guest Bike (1999 BMW R1100S).