Speedo is +5 or so percent higher than garmin based on observation. Interestingly, the odometer is only 0.36% higher on a 28 mile commute this morning. Tracking my distance all the way home the bike was about 0.1 miles high for almost the entire ride. I would say the odo is close enough for highway work. And it is good news cause my mpg was 72.5 the last fillup and my odometer is spot on.

 

My 2012 model, just put in service in june15, odom is consistently 5 mph over actual mph according to many of those portable radar trailers put up in the hoods to measure your mph.

 

I recently started using a GPS bicycle computer for speed and bread crumb mapping post ride.
GPS says 30, speedo is 33; GPS 40, speedo 44; and so on for the rest.
I knew the speedo wasn't right because I kept passing cops doing about 5mph over the limit, or so I thought. Until I did some investigation.
Oddly, my odometer is spot on according to highway mile markers.

 

Garmin devices are not known for their accuracy (although most of the complaints are with the elevation function).

The **** fell off my odo reset, so that doesn't work now either.