[deviousalex]

I've been reading around on the interwebs and I'm a little confused. Some people are saying that with a PowerTap hub you don't need to use a wheel magnet because the hub will do it. Others seem to think you do. Does anyone know what I should really do?

 

[mikerp]

http://forums.roadbikereview.com/ra...iathlons/powertap-garmin-500-n00b-207919.html

 

[RServranckx]

I've been reading around on the interwebs and I'm a little confused. Some people are saying that with a PowerTap hub you don't need to use a wheel magnet because the hub will do it. Others seem to think you do. Does anyone know what I should really do?

You do not need a wheel magnet - the PowerTap accurately reports the wheel rotation.

However, for cadence, I'd recommended to use the pedal magnet. While the PowerTap reports cadence, it is only based on power fluctuations rather than actual pedal rotation - if you're soft pedaling, the PT may report 0 cadence.

Rob

 

[deviousalex]

You do not need a wheel magnet - the PowerTap accurately reports the wheel rotation.

However, for cadence, I'd recommended to use the pedal magnet. While the PowerTap reports cadence, it is only based on power fluctuations rather than actual pedal rotation - if you're soft pedaling, the PT may report 0 cadence.

Rob

Thanks, this is the setup I'm trying to achieve but I'm having problems. So I removed the speed magnet but left the pedal magnet in place. With the bike upside down and the GPS started I started to pedal. Speed would start going up but cadence seems to remain at 0. I tried repairing the sensor and pedaling but it never said "Cadence sensor detected".

According to DCRainMaker cadence will be reported from the PowerTap first, I'm not sure if this is true. I've read on most sites that garmin will have the GSC-10 as the primary source.

In most head unit configurations (that’s the display unit), cadence information from a power meter will always override cadence information from a separate standalone sensor.

The ANT+ Bike Speed/Cadence Sensor: Everything you ever wanted to know | DC Rainmaker

Anyone else run into this?

 

[Pirx]

However, for cadence, I'd recommended to use the pedal magnet. While the PowerTap reports cadence, it is only based on power fluctuations rather than actual pedal rotation - if you're soft pedaling, the PT may report 0 cadence.

Yes, the cadence that the PowerTap reports is usually very noisy, meaning it's often inaccurate, since the PowerTap is trying to guess your cadence form the torque fluctuations that the hub sees. If you are pedaling along a nice, smooth rode, at a very nice and even stroke, that works alright, but a lot of times it doesn't. Oh, and at least for Garmin head units, the dedicated cadence sensor (GSC-10 for Garmin, or the built-in thingie that some Treks have) always overrides the PowerTap, as it should, so Rainmaker is (uncharacteristically) wrong on that one.

 

[deviousalex]

Well, I seemed to fix that issue by un-syncing everything then doing the Cadence, then PowerTap, then HR monitor. I was still having issues with auto wheel sizing (it set it to like 1700mm instead of the normal 2096mm).

Now the question is, this isn't the only wheel I have. How will things work out when I swap wheels to one that isn't a powertap and has a spoke magnet.

I had better actually start trianing with power or else this is all too much of a headache!

 

[RServranckx]

Now the question is, this isn't the only wheel I have. How will things work out when I swap wheels to one that isn't a powertap and has a spoke magnet.

I had better actually start trianing with power or else this is all too much of a headache!

As the PowerTap is not present nor transmitting with your other wheel, all data will be coming from the GSC-10 (cadence, possible speed if no GPS). No issues nor confusion here for the head unit. I have a similar setup (1 wheel with PT, one without) and I don't need to do anything for it to all work - it's automatic.

If you use different tire/wheel sizes, you will need to change the wheel circumference information on the Garmin head unit when you swap wheels -this takes about 30 seconds.

Rob