Kolelo

I was going to enter in a custom wheel size in the setting but I keep getting 2117 mm instead of 2096 mm when I measure my 700x23 GP 4000S tires. So I'm thinking it may be best to leave it on auto.

You guys have your Garmin bike wheel size setting on "Auto" or "Custom"?

svtmike

I have mine on Custom. My GP 4000S measured out at 2108 when I did it.

Accordion

Maybe I've had a few too many Fat Tires tonight but the 500 is GPS-based. Why would it need to know your wheel size?

svtmike

It'll take the speed from a PowerTap or a Speed/Cadence sensor if present rather than the GPS, because they are more accurate and not subject to reception issues.

lynch.cr

I have mine set to Auto, but i have only gotten a few rides in since I got my 500 and have just used GPS for distance calculation so far. Still new to the Garmin scene. I am just happy to have an abundance of data. Now I have to figure out what to do with it.

deepakvrao

Dunno about the 500, but the 305 and 705 take the speed from the wheel only when GPS is unavailable.

svtmike

https://forums.garmin.com/showthread.php?t=9176

Put your bike on a stand out on the driveway where you have GPS reception and spin the wheel. You'll get a speed reading without movement.

chasmm

The Garmin Edge 500 gives priority to the GSC-10 speed/cadence sensor when it is present. If it isn't installed/hasn't been paired/isn't reading properly (magnets mis-aligned, for example), then the speed will come from the GPS.

On those occasions where my GSC-10 isn't registering and I've had to rely on the GPS for speed I've found that it can fluctuate pretty widely depending upon the tree coverage, buildings, etc.

I've read that Garmin recommends that if you use the "auto-calibration" setting that you try to ride a fairly straight line until the calibration has been completed.

And if you read this thread over on the Garmin forums, be sure to read the entire thread...there is some incorrect info in it that gets corrected at the bottom...

https://forums.garmin.com/showthread.php?t=9176

Charles

RaleighComp

Thanks, I'm waiting for my 500 to arrive and I'm using the same tires.

Kolelo

I remeasured with me riding the bike and got 2086 mm consistantly. I would have thought that 200 lbs of me on it would have made for a longer roll out than that measured with no weight on the bike, 2117 mm. Go figure.

Accordion

Whoa! I am really glad I asked that question! The whole point of having a 500 for me would be to get rid of the magnet and the sensor. I thought it would be awesome just to have the head unit and use the GPS for all calculations.

The fact that they recommend you use the magnet is disturbing to me.

I used to ride my mountain bike on the road for a 23 mile loop with my GPSMAP 60CSX handlebar mounted. It never lost signal and was always within a tenth of a mile or so of the distances.

Interesting.

chasmm

I'm not familiar with the 60CSX...does it use WAAS by any chance? If so then it picks up land-based signals to augment the GPS. Just a thought.

I haven't ridden any real distance without the GSC-10, so I can't vouch for it's accuracy over distance. Like I said, I did notice that the speed can fluctuate at times.

That said, I originally had the blue Edge 500 and when the black/neutral one came out I got that one, and sold the blue one to a guy in my club. He uses it without the speed/cadence sensor and is happy with it. I know me, though, and I'm just too anal...it would drive me crazy "knowing" it wasn't as accurate as it could be.

Charles

Dolamite02

I have mine on custom, but despite my careful, drunken measurements of a tape against the ground compared to my wheel, I kept getting a measurement that was off the scale to what the book was.

I'd seriously suggest setting a piece of masking tape on the ground, and very carefully measuring the circumference of the front wheel. I effed it up, and it's easy to do. Basic as it may seem, it took a second go around for me to believe I'd fouled up by as much as I had.

---EDIT---

Yes, mine is an Edge 500