Recently got the aluminum g3 set from powertap. And I must admit, I love this thing! Didn’t even know that it calculated it’s own cadence, albeit, rough around the edges during some good instances. So I’m looking at the new garmin accelometer cadence sensor, but my question is, do my garmin head units (310xt and 510) take the cadence from the powertap over the cadence sensor?
Cadence defaults to the cadence sensor over the Powertap but speed/distance defaults to the powertap over any speed sensors…
Joel
if you just use cadence casually, you might just stick with the G3 cadence.
If you use cadence for deep science (like force/velocity plots), you might not want to use accelerometer cadence. Maybe the garmin’s setup is close enough to perfect though, should look into that.
According to Garmin it will use the cadence sensor over the powertap but I can tell you from first-hand experience I don’t necessarily believe this. I have the G3 and a Garmin cadence sensor on my TT/Tri bike and If the battery dies on the power tap it will stop reading cadence which tells me it is using the Powertap. I’ve been able to get around this by switching bike profiles.
I just got my G3 HED Belgium a couple of weeks ago. How accurate is the distance/speed? It seems to be very accurate. It’s typically paired up with my 910XT if that matters. A rode a local century and it was over a mile off (high), but then I rode a local metric century and it was right on the money. I realize the century course could have been long. I’m not complaining about it being off my a mile or so on a century (if it even was), I’m just curious. Plus, I’d like to know exactly where I’m at on the 116+ mile bike course at IM Chattanooga in a couple of weeks. 
distance/speed will be very accurate, as long as you input the correct tire circumference. If you are in need of super high accuracy it is probably worth measuring it, tires differ. The powertap knows very very accuratel when it has rotated a certain amount, it has to in order to compute power. But to know when your feet have rotated once, it has to do some guessing.
I just got my G3 HED Belgium a couple of weeks ago. How accurate is the distance/speed? It seems to be very accurate. It’s typically paired up with my 910XT if that matters. A rode a local century and it was over a mile off (high), but then I rode a local metric century and it was right on the money. I realize the century course could have been long. I’m not complaining about it being off my a mile or so on a century (if it even was), I’m just curious. Plus, I’d like to know exactly where I’m at on the 116+ mile bike course at IM Chattanooga in a couple of weeks.
I haven’t been able to find out how to accomplish this with a 910XT, only for the Powertap head unit. I have used the Googles, but without any luck. Maybe I am using the wrong phrasing? Every time I search it I only come up with results for the 910XT calibrate/zero function.
distance/speed will be very accurate, as long as you input the correct tire circumference. If you are in need of super high accuracy it is probably worth measuring it, tires differ. The powertap knows very very accuratel when it has rotated a certain amount, it has to in order to compute power. But to know when your feet have rotated once, it has to do some guessing.
I just got my G3 HED Belgium a couple of weeks ago. How accurate is the distance/speed? It seems to be very accurate. It’s typically paired up with my 910XT if that matters. A rode a local century and it was over a mile off (high), but then I rode a local metric century and it was right on the money. I realize the century course could have been long. I’m not complaining about it being off my a mile or so on a century (if it even was), I’m just curious. Plus, I’d like to know exactly where I’m at on the 116+ mile bike course at IM Chattanooga in a couple of weeks.
Google around about “wheel size”
You have to tell it to use the wheel sensor, or it will use GPS and not give you an option to set wheel size.
I haven’t been able to find out how to accomplish this with a 910XT, only for the Powertap head unit. I have used the Googles, but without any luck. Maybe I am using the wrong phrasing? Every time I search it I only come up with results for the 910XT calibrate/zero function.
distance/speed will be very accurate, as long as you input the correct tire circumference. If you are in need of super high accuracy it is probably worth measuring it, tires differ. The powertap knows very very accuratel when it has rotated a certain amount, it has to in order to compute power. But to know when your feet have rotated once, it has to do some guessing.
I just got my G3 HED Belgium a couple of weeks ago. How accurate is the distance/speed? It seems to be very accurate. It’s typically paired up with my 910XT if that matters. A rode a local century and it was over a mile off (high), but then I rode a local metric century and it was right on the money. I realize the century course could have been long. I’m not complaining about it being off my a mile or so on a century (if it even was), I’m just curious. Plus, I’d like to know exactly where I’m at on the 116+ mile bike course at IM Chattanooga in a couple of weeks.
Google around about “wheel size”
You have to tell it to use the wheel sensor, or it will use GPS and not give you an option to set wheel size.
How do you tell a 910xt to use the powertap for speed/cadence and not the GPS? I thought it did that automatically once you had it find the powertap – without any way for the user to enable/disable it
I guess I was thinking it was changing something in the PT, but it is actually just a matter of how the head unit (no matter which one) interprets it? I already had my wheel size manually set from where I measured it when I had the stock rear wheel so I’m guessing it’s close, even being on a different wheel. I will measure it again once I change the Specialized Turbo Elite over to a Continental 4000s before my IM. Sorry for the threadjack…
Google around about “wheel size”
You have to tell it to use the wheel sensor, or it will use GPS and not give you an option to set wheel size.
I haven’t been able to find out how to accomplish this with a 910XT, only for the Powertap head unit. I have used the Googles, but without any luck. Maybe I am using the wrong phrasing? Every time I search it I only come up with results for the 910XT calibrate/zero function.
distance/speed will be very accurate, as long as you input the correct tire circumference. If you are in need of super high accuracy it is probably worth measuring it, tires differ. The powertap knows very very accuratel when it has rotated a certain amount, it has to in order to compute power. But to know when your feet have rotated once, it has to do some guessing.
I just got my G3 HED Belgium a couple of weeks ago. How accurate is the distance/speed? It seems to be very accurate. It’s typically paired up with my 910XT if that matters. A rode a local century and it was over a mile off (high), but then I rode a local metric century and it was right on the money. I realize the century course could have been long. I’m not complaining about it being off my a mile or so on a century (if it even was), I’m just curious. Plus, I’d like to know exactly where I’m at on the 116+ mile bike course at IM Chattanooga in a couple of weeks.
For me the garmin uses the cadence sensor over the PT for cadence. I know because the crank arm magnet fell off my TT bike; cadence data is pretty choppy on the TT bike and smooth on the road bike. It doesn’t bother me except when I ride a trainer where it I find it easier to adjust cadence for increase/decreases in power rather than chase a watt number up and down.
Does speed default to the G3 PT over the 910xt GPS? If so I let my 910xt calculate wheel size automatically which I assume is based on GPS distance. Just not sure what the 910 uses between GPS and G3PT when displaying speed and distance.
I guess I was thinking it was changing something in the PT, but it is actually just a matter of how the head unit (no matter which one) interprets it?
yes, just the head unit.
Garmin cadence sensor on my TT/Tri bike and If the battery dies on the power tap it will stop reading cadence which tells me it is using the Powertap.
This is not true for me. The battery went out on my cadence sensor once, and cadence readings became erratic, so I know the external cadence sensor has higher precedence over the PT. This has been confirmed by Garmin developers in the Garmin forums.
I believe speed always defaults to the powertap or to the the speed/cadence device over GPS (because assuming you have a correct wheel size those devices are more accurate). The reason why I think this is that I had my speed/cadence sensor snap off during a race last weekend and for about 2 or 3 miles it did not register anything for speed or distance until finally the GPS took over. Also I always put in the wheel size manually because I have found that to be more accurate than the automatic GPS calibration for wheel size.
Joel
I believe speed always defaults to the powertap or to the the speed/cadence device over GPS
Not if you did not select manual wheel size. Default is GPS.
That is interesting and makes sense for me at least since I always set my wheel size manually that I would see that as the default behavior… The only thing I found in the edge 500 or forerunner 310XT manual was that with auto the wheel size was set with GPS but I could not find anything in there indicating the preference other than if you don’t have the cadence sensor installed it uses the GPS data for speed and distance which is a no brainer since that is all the data you have…
Joel
You can easily verify this by setting your wheel size to auto, then notice that your speed would fluctuate between 0 and 0.1 in the Garmin even when the bike is stationary. This would confirm that the Garmin is getting speed data from GPS instead of from the PT.
That is interesting and makes sense for me at least since I always set my wheel size manually that I would see that as the default behavior… The only thing I found in the edge 500 or forerunner 310XT manual was that with auto the wheel size was set with GPS but I could not find anything in there indicating the preference other than if you don’t have the cadence sensor installed it uses the GPS data for speed and distance which is a no brainer since that is all the data you have…
Joel
My recollection is that if you pair a the GSC10 speed and cadence sensor to the 500 head unit, it defaults to speed and cadence from the GSC10. The PT head is pretty good at speed, but less accurate for cadence
Garmin cadence sensor on my TT/Tri bike and If the battery dies on the power tap it will stop reading cadence which tells me it is using the Powertap.
This is not true for me. The battery went out on my cadence sensor once, and cadence readings became erratic, so I know the external cadence sensor has higher precedence over the PT. This has been confirmed by Garmin developers in the Garmin forums.
Agreed that that is certainly what Garmin says but mine definitely doesn’t work that way.