PowerTap P1 pedals and TR iOS app


#1

I have recently started using P1 pedals (with left and right power measurement) in conjunction with my Kickr Snap smart trainer using the power match settings. This has worked very well and I am very happy not to have to stop after 10 minutes to perform a spindown calibration.

My only question is whether in the transmission of power readings from the pedals to my iPhone via Bluetooth the reading from one pedal is being doubled or if the contribution from each pedal is measured separately? I ask because when doing single leg drills on the right leg, the power reading is zero despite my left leg being engaged and producing force.

Sorry if this has been covered already.


#2

Yes, just doubles the left leg.


#3

Thanks very much. Do you happen to know if this it also doubles the left leg if I transmit via ANT+?


#4

ANT+ is true dual sided.


#5

Is there a pedal-based power meter that transmits dual-sided with bluetooth? It seems like Ant+ is going to die a slow death with the lack of updates to Ant+ sensors like Wahoo’s iOS sensor.


#6

My understanding is that it’s not a Bluetooth issue but rather a TrainerRoad issue that they’re working on resolving. Your pedals are transmitting two separate signals but TrainerRoad can’t currently combine them and make them match appropriately as part of the Bluetooth transmission.


#7

Note that recently TR tech support told me I still need to do spin downs on my Kickr even when using my P1’s and Powermatch. Not sure why and never got a further explanation.


#8

I don’t think that’s correct.


#9

We have gotten comments that it isn’t necessary, but it may improve results, if you do a calibration on the trainer. That is about as solid as it can be.

  • The “Your Mileage” Will Vary" statement applies simple due to the large variety of trainers and power meters and all of the possible combinations.
  • Now, as ever before, do some testing on your exact setup, evaluate the results, and apply what seems to work best.

#10

@DonTrail You can set the Kickr Snap to use the P1 ANT+ broadcast as the source for power in the Wahoo Fitness app using the ANT+ ID, then connect the P1 to your iPhone but check the box that says “Only use for cadence” in the device settings. That will allow the kickr to take both sides of power in and send that to your iPhone.


#11

Take it up with Lauren Echo of Trainerroad who wrote me the following:

" My Current Suggestions …

  1. Make sure that you are calibrating your P1’s and KICKR before every ride. It’s very important that you calibrate both of these devices separately because we still take both power readings into consideration when using PowerMatch. You can calibrate in either the TR app or the PowerTap and Wahoo apps. This is because calibration occurs internally and will carry over to different apps."

#12

Thanks Jon. I will try this.


#13

I Heard @Nate once say in one of the podcast that typically you dont need to do a spin down when using KICKR and P1. only do the Calibration on your pedals

Something long those lines


#14

This is confusing. I contacted TrainerRoad support recently and that is not what they said. They told me to contact PowerTap.

I learned that after I learned that BLE doesnt read power from both pedals. ANT+ would but not BLE


#15

See my response to pvolb above - that message was from Trainerroad technical support on 1/22/2019.


#16

then Tech Support isn’t consistent in their response. I literally open a ticket about a week ago


#17

In the podcasts, Nate initially mentioned you should never need to do a spindown when using Power Match but he walked that back in later episodes I believe. I don’t do a spindown EVERY workout, but I’ll do it once or twice a week (assuming I have 5 indoor workouts in the week).

Just do the silly spindown and get on with your workouts. :smiley:


#18

Yes, ask a different person… and you get a different answer…

This is one example of many, that I have seen from TR reps.

Clearly, they haven’t locked in and shared an official company line.


#19

I would think you’d have to calibrate both when using power match since it’s taking the difference between the trainer and the pedals and coming up with the “actual” number.


#20

That’s not really true. The power meter is always the “actual/real” power number.

PowerMatch reads the differential between the power meter and smart trainer all the time in the workout. It finds the differential between the two, and sets the trainer resistance in order to hit the right power target, according to the power meter.

Example:
When you start into an interval with 200w power target:

  • TrainerRoad takes the data from the power meter as the “right” one.

  • Let’s say the Power meter reports 200w

  • Let’s say the trainer reads low and reports 180w.

  • The delta is 20w as the trainer reads “low”.

  • What Power Match does is read that difference between the meter and trainer, and adjust the trainer resistance unit to hit the target, according to the power meter.

When the power target increases to 250w:

  • TrainerRoad increase the trainer resistance by about 20w,
  • Then the power meter reports a new power from this adjustment. Assuming the meter and trainer have a different power curve slope (very likely) we might see a 25w differential at this power output (i.e. not a linear 20w adjustment at all points).
  • It does this actively and tries to predict the trend via machine learning in effort to keep the target power close via the power meter. The trainer is secondary and set to reach the first goal.

I wrote my example above from memory. Here is the actual Power Match article that likely does a better job of explaining than I tried.