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Do I need all these sensors?
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I've gotten my new power meter (PowerTap C1, not installed, waiting on tools) and the unit is supposed to transmit cadence, but I already have a speed/cadence sensor on the bike.

Is it fine to use both? Should I replace the S/C with a speed only one? Should I just ditch the S/C completely and skip distance tracking on the trainer?
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Re: Do I need all these sensors? [Socket] [ In reply to ]
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I would ditch the extra cadence sensor and only use the sensor in the PM. That is what I did on my bike. It is cosmetically cleaner, lighter, and simpler. I kept the speed sensor on my bike. Eventually, I got a direct drive trainer, which killed the usefulness of the speed sensor on the trainer (but the trainer took that over anyway). I moved the speed sensor to the front wheel for outdoor riding only.
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Re: Do I need all these sensors? [Socket] [ In reply to ]
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While the C1 does have cadence and speed built in, it supposedly is not as accurate as if you were to have a separate cadence and speed sensor. I have a PowerTap hub and finally ditched the cadence sensor as it is a metric that is just not as important as watts or other metrics. That and I was tired of using zip ties to put it on every time I wanted to give a good wash to my bike. Personal preference I suppose.
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Re: Do I need all these sensors? [Socket] [ In reply to ]
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I use my smart trainer to determine power indoors rather than my C1. So I keep a dedicated cadence sensor on that I take off before a race.

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Re: Do I need all these sensors? [Socket] [ In reply to ]
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I got rid of both speed and cadence sensors when I got my power meter. I realize it can be used on a trainer and add to the accuracy of a GPS. But speed really isn't that necessary of a number for me once I got the power metric. One less thing I have to worry about being on the bike and connecting with the head unit.
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Re: Do I need all these sensors? [KG6] [ In reply to ]
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Agree I don't have a speed display any more on my display. Power, cadence and heart rate is all that concerns me. Racing if pushing into a strong wind and you are fatigued it can play negatively in the mind and is irrelevant in training so I got rid of it. Best thing I ever did.
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Re: Do I need all these sensors? [Shambolic] [ In reply to ]
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Sounds like I don't really need both, which is cool because I can move this s/c unit to my road bike.

I do still want speed just to track distance on trainer (which technically doesn't mean anything, but I like to see it), so I'll look for a speed only sensor.

Thanks for the help 👍
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Re: Do I need all these sensors? [Socket] [ In reply to ]
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Socket wrote:
I've gotten my new power meter (PowerTap C1, not installed, waiting on tools) and the unit is supposed to transmit cadence, but I already have a speed/cadence sensor on the bike.

Is it fine to use both? Should I replace the S/C with a speed only one? Should I just ditch the S/C completely and skip distance tracking on the trainer?

I don't think a Garmin Device can take data from different devices sending the same information. You can try and let us know what happens but I thing the head unit will probably do the electronic version of puking.

Power Meter cadence readings are dead on. They won't work without it, since power is really just how hard you push on the pedals times how fast the pedals are moving. If they didn't measure one correctly the power reading would be garbage.

As for a speed reading, you don't really need it on a dumb trainer since you are really interested in time at power. If you are using a smart trainer and graphical based software then that is different. My only experience is a Magnus trainer using Rouvey, but Rouvey needs distance to show your progress on the screen. On a dumb trainer it does this with an algorithm based on power and weight. On the Magnus it reads the speed sensor built into the trainer. We tried the dumb trainer and a speed sensor and it ignored its output. Makes sense since the speed being reported is incorrect when the program goes up or down a hill. It can't change resistance.

"...the street finds its own uses for things"
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Re: Do I need all these sensors? [AutomaticJack] [ In reply to ]
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AutomaticJack wrote:
Power Meter cadence readings are dead on. They won't work without it, since power is really just how hard you push on the pedals times how fast the pedals are moving. If they didn't measure one correctly the power reading would be garbage.

The reply above specifically mentioned a powertap hub. Those don't need cadence and are pretty bad at guessing. I'd assume the C1 rings are plenty good, but have no experience.
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Re: Do I need all these sensors? [dfroelich] [ In reply to ]
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You are correct. The hub based Power Taps are very accurate at knowing wheel speed (for the reasons I gave) but fail in cadence because they have to guess at the rotation of the crank based on pulses in power. I never had one but I believe Power Tap made a cadence sensor for the crank for just this reason.

"...the street finds its own uses for things"
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Re: Do I need all these sensors? [Shambolic] [ In reply to ]
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I have distance but speed m/hr or km/hr here in Australia I no longer have on any of my data screens.

Outdoors on my Garmin I basically use one screen that I use to race. HR, power, cadence, elapsed time, distance and average power.

Trainer. HR, power, cadence, elapsed time, current lap. I figure distance on a trainer is irrelevant.
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