Garmin 800 wrong mileage and avg speed

Quins

I noticed that my 800 had recorded the wrong mileage and speed on my commute this morning. Not happened before.

I used it on Saturday, club ride, checked profile for the bike I was on, recorded in line with everyone else. Changed the profile to commuter bike this morning noticed that the mileage was already 18 miles after only about 6, my average speed was showing as 43mph? The avg speed then began to drop over the course of the (14 mile) commute but only into the 30s.

On Saturday I used gsc10, commute bike doesn't have it.

Any idea what's going on? The only other thing I can think of is that a gel did splash on the unit on Saturday, not much , but at the bottom right on the screen....it still recorded that ride ok.

slowbike

The 800 is pretty much waterproof - so no bother with the Gel.

The additional mileage is just a calculation from start point to where you were when the GPS picked up - I guess the club run didn't stop at your home? If you convert the fit file to GPX you'd be able to see where the first few points have been recorded then a massive gap.

Quins

I stopped the unit when I got home, club run was about 60 miles, garmin clocked 70 at the end which correct for the ride in and back. I used stop then re set, then loaded it onto strava, it all tallied up. The unit had been sat indoors since, I don't understand the average speed starting off at 43mph ( that happened to be the fastest speed on the club run, down hill!) God knows what I've done to it this morning, blaming Brexit..

wongataa

Did you start riding before you had a GPS lock? That can cause such issues as your position can suddenly change when you get lock.

fenix

Sounds like dodgy GPS lock to me. Can't you see where the garmin says you started ?

step83

I get this on mine if you start a ride without it locking, itll pip that movements detected then when you unit yes its basically guessing where you are still so youll get some weird jumps.
Even if you had the speed sensor attached its not fixed your location yet so can still do odd leaps.

benjamess

Step83 wrote:

I get this on mine if you start a ride without it locking, itll pip that movements detected then when you unit yes its basically guessing where you are still so youll get some weird jumps.
Even if you had the speed sensor attached its not fixed your location yet so can still do odd leaps.

had it happen to me to, once uploaded to strava I had a massive straight line from about 10 miles away to the start of my ride, I just seen it as reclaiming some miles my garmin had previously stolen from me

redvee

I'v e had a couple of rides with initial dodgy GPS locks. Didn't really notice it till I got to a point that I knew the distance of and my 820 showed an extra 2 miles. Upload the ride to Strave etc and have a look at the ride details.

Quins

Thanks for all the replies, good to know that I'm not alone and it's a sporadic issue, the return leg was recorded without problems. @benjames I like your thinking about reclaiming the mileage, that made me chuckle.

rolf_f

Happens to me when the battery in the speed/cadence sensor is on its way out. Always seems to record double for some reason.

The massive straight line you can edit out in the gpx or just crop in Strava.