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LEVERICK
03-29-2010, 11:09 AM
Just got my Edge 500 mounted on my mountain bike and did a test ride yesterday. Seems like everything works well. I also have the HR and Cadence gear as well.

One question, In the speed sensor setup I can choose auto or enter the value for calibration. If I run in auto, is it calculating speed and distance using the GPS only and not the wheel sensor? I assume if I enter my wheel calibration value 2275 (29er wheel setup), it will use the wheel sensor exclusively for speed and distance?

T_SMIT
03-29-2010, 11:24 AM
If you know the rolling radius of your tire then it's best to just enter that value and make sure that the calibration doesn't get set to Auto.

On Auto calibration, the Edge uses GPS information at the start of each ride to set the cal factor, and then uses that value to process your speed sensor data for the remainder of the ride. That's convenient if you change tires or wheels frequently, but if you start out your ride with a poor GPS position solution then your cal factor may end up being set to a bad value and you'll get odd speed readings for the ride.

The Edge will default to your speed/cadence sensor for realtime speed and distance display if it detects your GSC10 at the start of the ride. I don't know how this information is integrated into post-ride analysis.

SAEEDI
03-29-2010, 12:34 PM
One thing about mountain bikes and auto-calibration of the wheel size is to be sure you're riding on a straight trail until you hear the tone the calibration has been set. If you hit the switchbacks right away, the calibration will never happen and your speed/distances will be off for the duration of the ride.

BBECKER39
03-29-2010, 12:53 PM
The GSC10 sensor will be used for realtime speed and distance, as well as recorded speed and distance as long as it is in a calibrated state. The only time it is not considered to be calibrated is when it has been set to Auto and has not completed an auto calibration.

When using the Auto setting, the unit will continually auto calibrate the sensor using GPS. It is possible for an inaccurate calibration to occur, but this error should get corrected by subsequent calibrations. Significantly inaccurate calibrations are not likely because the unit will only calibrate the sensor durring periods of ideal GPS coverage.

MS6073
03-29-2010, 02:33 PM
One thing about mountain bikes and auto-calibration of the wheel size is to be sure you're riding on a straight trail until you hear the tone the calibration has been set.

Ah, so that is what that was this morning shortly after starting out on my time trial bike for the first time with the Edge 500. Not sure if this is relevant, but when I set the circumference for my road bike, I consulted the chart in the Edge User Manual and noted that Garmin publishes circumference values of 2086 for 700x20 (2096 for 700x23) while other computer manufactuers such as Polar list a value of 2051 for 700x20 so why the discrepancy?

ROBERTDAINES
03-29-2010, 03:45 PM
I think that the values that Garmin uses are the more common ones (at least they are the same as Cateye, among others). If you want to be as exact as possible, you can measure it yourself. You just need to measure off one full rotation of the wheel while you are on the bike. For my 700x23 tires, I just use the 2096 value and don't worry about it.

XCAMRIDER
03-30-2010, 12:46 PM
One thing about mountain bikes and auto-calibration of the wheel size is to be sure you're riding on a straight trail until you hear the tone the calibration has been set. If you hit the switchbacks right away, the calibration will never happen and your speed/distances will be off for the duration of the ride.

This is the first time I have heard of this. I did not see it mentioned in the manual but I admit that I have not done an extensive search for it either. Is it better to manually enter the wheel circumference instead of auto calcualting it when I mountain bike? I usually let the unit acquire satelllites for a few minutes, throw it on the bike and I am off into the woods.

KLAUS.BARTOSCH
08-23-2011, 12:35 AM
What is better? Setting the Garmin setting to Auto or setting it via the wheel circumfrance? Which is more reliable/accurate?

DW152
08-23-2011, 01:48 AM
What is better? Setting the Garmin setting to Auto or setting it via the wheel circumfrance? Which is more reliable/accurate?

Definitely use a custom setting using the wheel's circumference, and set it once and for all.