Saturday, October 29, 2011

Garmin Forerunner 305, Sigma, Android computer telemetry and cadence sensor. 

Just how many bike computers do you really need?  Seems like I now have three.  My original Sigma computer with heart monitor, the Android HTC myTouch, and now the Garmin Forerunner 305 and ANT+ heart monitor and cadence sensor.  All of course give slightly different results and features and strengths.

The Sigma gives the most accurate speed, distance, altitude and heart rate because it is mounted on the bike and measuring directly off the wheel rotation using the wheel diameter.  The Sigma has no GPS or storage and download however so its only useful for immediate riding and overall statistics.  The on bike display is highly visible and provides instant diagnostics and feedback.

Next the HTC Android running Google myTracks does a terrific job.  The GPS calculation accuracy is within 1% of the Sigma bike measurements primarily because of the high sampling rate every 0.5 seconds - essential for bike riding.  Uploading to online tracking sites of the ride GPX files is quick and easy. However, there is no heart rate monitor or cadence and adding those devices is problematic as HTC is using Bluetooth connections.  I keep the HTC in my back shirt pocket so it cannot "see" the heart rate monitor on my front chest, nor is there a cadence sensor available.  This means tracking winter indoor rides on rollers or trainer is not possible.

Enter the Garmin Forerunner 305 which Walmart is now selling.  How mainstream is that for a running/bike geek device?!  The price varies though wildly, somehow linked to tides and moon phases.  So much for Walmart's RollBack - all I've seen is roll up - going from $137.95 to $175.95 in matter of two weeks!

I purchased mine off eBay using some eBucks credit - so that meant I got a great deal.  I then found the Garmin GSC 10 cadence device on Amazon for $30 with free shipping.  These devices would have cost you well north of $300 together a couple of years back.  Getting the GSC 10 working on my Bike Friday with 451 20" wheels however required some ingenuity to mount it successfully.

Garmin provide an additional rubber mount - and I used that one on top of the Paul brake arm, making a cut out on the inside of the rubber to accommodate the bolt on the brake pad retainer.  The wheel magnet goes on the spoke nipple to reach the sensor arm on the GSC 10.  Then the cadence magnet goes on the inside of the crank arm and while it is slightly ahead of the GSC 10 that still works fine.

Now to get the Garmin Forerunner 305 working optimally you have to remember the following:

1) Switch the 305 on outside and place it down away from buildings so the GPS satellite detection can work. That can take a minute or two - so go do something else while that happens.
2) For better accuracy set the data sampling rate to every 1 second, and not the automatic mode.
3) The cadence sensor wheel rotation is ignored when calculating speed and distance if the 305 can see GPS satellites.
4) Set the pause speed to be 2mph - so if you have to stop the 305 pauses recording
5) Before each ride remember to press down and hold the lap button (on left) until it does a Reset.
6) Press the start activity button and then don't forget to press it again to stop activity when you are done.
7) I wear the 305 with the display face down on the inside of my left wrist - that way a slight wrist rotation shows me quick glance at metrics as I'm riding.  But for riding in trees or poor reception, wear it face up.
8) Use the Connect.Garmin web site for logging activity - it is way better than the Garmin Training Center software provided with the 305.

Some things I find annoying about the 305 -

1) You have to switch it off - it does not switch itself off after say 15 minutes of no activity
2) No full GPX export capability with speed, heart rate, cadence - you can only export the GPS route track
3) You cannot make it use the cadence sensor wheel speed calculator as the main distance and speed device.
4) You cannot set the sampling rate to 0.5 seconds - which would be much more accurate for bike riding.
5) Having to wait while it scans for satellites - it should remember home setting and offer to skip the scan.

Otherwise the 305 is awesome.  For the price it provides superb features and works with all the major online tracking sites that have Garmin interfaces.  Also the GPS positioning is a lot more accurate than in the Android phones.  Google's myTracks software does some clever faking, but if you compare rides side by side, you see the Garmin positional accuracy to 5x more precise.

I now use just the Garmin and Strava and connect.garmin.com sites. The Sigma is still the best for on bike display and metrics. I guess we just have to accept there is no one solution for now - until someone comes out with something that is clearly better  and at a price that is affordable.  Still by investing in ANT+ sensor devices that should be a win-win going forward.

Last but not least DC Rainmaker here provides the fullest review and information here on using the 305 for everything and more than you ever thought of.  Kudos to him!

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