This is my second 305--the first had the well-known loose battery problem, and would spontaneously shut off in mid-ride. Though long out of warranty Garmin replaced it with a refurbished unit (yay, Garmin), which works reliably and perfectly.

EXCEPT: I have the until set up so that one display window shows cumulative altitude gain. The display routinely shows 15% or so less altitude gain then is actually the case--no matter how long or hilly the ride. When I download the data to my desktop the correct altitude is transferred!

I find this baffling and annoying. Any ideas? No one I've talked to has ever heard of such a thing before.

I see different numbers on the machine, the garmin software, and other brands of software. Described here:

https://www.bikeforums.net/showthread...nt-conclusions

Thanks so much for the quick reply. I use both the Garmin Center and Ascent, and the elevation gain figures on both programs always agree with each other. It's the display on the 305's screen that's off. I've checked this against others' computers and known climbs. As I said, puzzling.

Reset to factory specs then reupdate the firmware?