# Garmin 520/820 multiple wheel/bike profiles



## L84Beer (Jun 24, 2015)

I have never worked with a Garmin bike gps device previously, but I am curious to know now the Garmin 8/520 devices keep track of multiple bikes and wheel sizes? I.e. if I buy one of these gps devices, and have separate speed and cadence sensors for each bike, is the device smart enough to figure out which bike/wheel size I am riding on the basis of the speed and cadence sensors it pairs with?

Are there fields/settings/profiles that I need to program to aid in this?

I find the user manuals to be horrible at explaining or helping to understand how to configure and set up profiles or settings....


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## WR304 (Jul 9, 2004)

Have a look at Post #55 here:

http://forums.mtbr.com/gps-hrm-bike-computer/garmin-edge-520-a-980371-post12193729.html#post12193729

Those pictures are for the activity profiles and sensor pool list on a Garmin Edge 520. A Garmin Edge 820 ought to be very similar.

With multiple speed sensors you would name each sensor to match the name of the bike that it is fitted to. Each speed sensor can have its own manual wheel circumference entered in the settings, so that the speed readings will be correct for each bike.

Within the sensor pool list of all the available sensors you can choose to enable or disable individual sensors. What I do with two bikes is to disable the sensors that I'm not using. Each bike has a speed sensor and power meter so I only enable the ones on the bike that I'm using that day.


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## csgaraglino (May 20, 2012)

I am going to have to disagree with most everything WR304 said above!

Here is my setup: I have a Garmin 1000 (same software as the 5/8xx series) and I have a Road, CX and Fat Bike. Road bike has 2 wheels, one for the road and one for the trainer. My Fatty has 3 sets of wheels - one 26" x 4.8" for the trails, 26" x 4.2" for the bike paths and dirt roads and 29+ x 3" for bikepacking and longer trail rides.

Currently, I have 1 HR Monitor, each bike has its own Cadence Sensor on the rank and every wheel has its own Speed Sensor.

However, before I got all the speed sensors, I did share them when switching wheels.

So far so good....

I'll address the Profiles - first profiles and sensors don't work in conjunction with each other, they are completely separate. The profiles are kind of useless, the only real reason to have more then one profile is if you want different Displays for a specific type of ride. For example, I have one for "riding" (any type) and it has 4 stat screens and 2 maps - and then one for the trainer. The trainer has only one screen display.

Now for the sensors: When you pair a sensor, you "can" name it if you want, but I have left mine with the default name which is the sensors ID number. When you have them all installed and paired - you DON'T need to do anything else. When it's time to ride, you just grab your bike and go. Once the wheel/crank makes 3 full rotations, the sensor(s) is activated and the Edge see that and uses that sensor(s) - it's that simple.

These sensors DO NOT care what the wheel circumference is! By default, they are set to Auto and will automatically compare revolutions to distance and calibrate accordingly. And it does this through the the whole ride. The only time you need to care about circumference is if your go to use a speed sensor in a situation without a GPS - such as when in a stationary trainer. And by default, if set to auto and no GPS data available, they use a default wheel size for a road bike wheel.

So you might ask, what's the point of a speed sensor when I have a GPS and using the GPS features? Good question! Most all GPSs hit the satellites in intervals and each GPSs intervals are different but it takes time to read satellite information and compare it to distance and calculate speed. And that delay is noticeable (to some) on the GPS Display with sudden acceleration or decelerations. With a speed sensor, the speed readings instant and accurate.

Note: the only time I have ever had an issue with not naming the sensors is if I activate more then one at a time and then the Garmin will warn you that it done 2 competing sensors and what's you to pick 1. This happened when I was swapping wheels and rolled the wheel I took off over to the bench (3 revs) and put the other one on. I don't do that any more 

Regards,
Chris Sgaraglino
My Life on Two Wheels
Widow Creek Photography


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## L84Beer (Jun 24, 2015)

So, profiles don't do much except put the workouts in sub-folders and allow for customization of screens; and different sensors don't do anything other than make for easier swapping of wheels/bikes? I.e. the auto wheel size determination that the gps does must be done on each ride, because the gps doesn't remember the last wheel size calculation it did with the paired sensor being used....seems silly? I thought the speed sensors were supposed to help with the speed and distance calculations of the gps, particularly when ridding in poor reception areas, like under tree canopy?


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## csgaraglino (May 20, 2012)

Correct.
Correct. Yes it will always calculate each time it starts, and mostly because most people only have one and will swap it between wheels/bikes. And that's eve end by how easy Garmin made it to mount and remove.
It does. And especially when the GPS signal gets blocked momentarily.

Regards,
Chris Sgaraglino
My Life on Two Wheels
Widow Creek Photography


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## Harold (Dec 23, 2003)

The Edge doesn't put rides done with different profiles into different folders. Different profiles simply allow you to change what is displayed on the screen. I have a couple different profiles for the same bike (my commuter) depending on what kind of ride I'm doing.

It really doesn't matter what sensors are being used with a given profile. Sensors like speed sensors associate with a single wheel. So the Edge does appear to remember the auto calibrated measurement from the last time you used it (I'm pretty sure, it seems that way on mine) and might update that number if there's a major discrepancy between the sensor and the GPS. This seems to do best when you're on a long, straight section. My 520 tells me when it updates the wheel circumference. It's only done that once on my road bike and it has not done it at all for my mtb.

It really does help with measuring distances. On an older GPS, I had a ride once where the GPS data went totally to hell. It was all over the place. But because I had a wheel sensor running, the distance I rode was spot on and I lost nothing for my annual tally.


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## WR304 (Jul 9, 2004)

On a Garmin Edge 520 the activity profiles do more than just let you choose what is displayed on screen.

If you go to Menu - History - Totals on a Garmin Edge 520 the individual distance covered is recorded for each separate activity profile. If you use a different profile for each bike then it acts as a device odometer to see how many miles you have done on each bike. 

The main thing to bear in mind with GPS distance and speed is that it isn't 100% exact to begin with. When it comes to speed sensors and auto wheel circumference calibration the Garmin Edge uses GPS to set the wheel circumference. Relying on that inexact GPS information as the basis for setting your wheel circumference means you are introducing additional potential for error into the readings. When you consider it can continuously recalibrate wheel circumference as well, changing during a ride, such as when riding round offroad with poor reception in woods, I don't see that as desirable.

By using a known measured manual tyre circumference set for a particular rider, tyre type and tyre pressure it removes this variable. With all these things, speed data, power data etc it's about consistency and trying to keep everything as "apples to apples" as possible for comparison between different rides.

Naming individual sensors isn't essential but is just a nice way of organising them for reference purposes. It's like filing your work documents so you can find them again. If it's all tidy to begin with it will save time in future if you ever need to do any troubleshooting.


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## Harold (Dec 23, 2003)

Sure, it will show on the device tallies, but the files are not stored anywhere differently, and the device's activity profiles do not do anything when you upload your ride to garmin connect.


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