When I connect my Stages Ultegra LR power meter (both left and right) via bluetooth the max power reading tops out around 80w when using TrainerRoad. When I connect the power meter via ANT+ the power reading is accurate and power match works fine, although ANT+ is only detecting and connecting a single power meter in the settings. Has anyone seen something similar?
No. Here is how I setup:
After installation of Stages LR:
- use Stages app to link left and right power meters
Setup in TR app:
- in iPhone TR app, pair via Bluetooth to the left power meter
- make sure PowerMatch is enabled
Now during an indoor trainer workout, the Stages left side will send total power (left+right) to TrainerRoad. And TrainerRoad app will compare workout power to Stages, and control trainer resistance.
In parallel I record all my inside workouts using Garmin Edge 530 bike computer via ANT+ and that records both left and right power (530 paired via ANT+ to left power meter). Comparing TR power to 530 power shows essentially the same power.
I thought TR could only read one crank arm when pairing Stages LR with Bluetooth and that only with ANT could you get both arms reading?
Yes and no. Both TR and Garmin only communicate with the left crank arm.
- TR records total (L+R) power, all data is sent from the left crank arm
- Garmin records both left and right, all data is sent from the left crank arm
There have been requests for TR to record both left and right data.
Right I understand that all data is sent from the left arm. However, I thought also that TR can only RECORD power from one crankarm when Bluetooth is used (depending on which arm you connect to) versus can record total (L+R) power only when connected via ANT?
No. TR can record total power using either Bluetooth or ANT+. I’m recording with:
- TrainerRoad via Bluetooth
- Edge 530 via ANT+
and they record essentially the same power. All data is sent by left crank arm of my Stages L+R Ultegra 8000.
Just went outside for a two minute test… at 40 seconds I unclipped left shoe and pedaled with only right foot as seen here in Garmin Connect:
^ that was recorded on Garmin Edge 530
Now lets see what TrainerRoad app on iPhone recorded… I pressed record on Garmin at same time as starting TrainerRoad… and TR has 5 second countdown and so its 5 seconds behind:
Both are showing 116W at the same time, and there is no power being applied to left pedal.
Conclusion: TrainerRoad is receiving power from right side via the Stages left crank power meter, over Bluetooth, and not simply doubling as stated in that post above.
@Bryce can you please comment on that?
This weekend I took a quick look at Bluetooth GATT specifications and as best I can tell the three relevant specs are the Cycling Power Profile, Cycling Power Service, and Fitness Machine Service (FTMS).
Loosely interpreting (I’m not an expert), the Cycling Power Profile v1.1 appears to specify in section 4.5 that if Stages is broadcasting left and right power, then TrainerRoad has three choices:
- display & record both left and right power
- calculate total power using both left and right
- estimate total power using only one side (e.g. doubling right side)
As shown in my quick testing, TrainerRoad appears to be calculating total power using both left and right. I’ve had the Stages LR since Nov/Dec 2018, and from the beginning I’ve been able to do TR workouts with single leg drills and see good power data.
The key to making this work is to use the Stages app and make sure the left and right meters are linked. You only need to do that once, after first installing the Stages LR (it is possible to unlink the left and right, and if that happens you need to link again).
Can I downvote that?
This thread is about Stages LR. I’ve done right leg pedaling, recorded with TR (Bluetooth) and Garmin 530 (ANT+).
- Garmin shows 0W left and 116W right
- TR shows 116W
If TR was doubling left side, it would show 0W. Instead it shows the power from right side. Which it received via Bluetooth from the left pedal. Because the left pedal was transmitting both left and right. TR correctly calculated total power L+R.
Just got an LR. Having some trouble linking them up. Are you saying you can do one leg TR drills and the right power will show up while you have the left pedal not clipped in?
yes. Use the Stages mobile app to link them. Then in TrainerRoad pair left side only.
Huh. Does it take a moment to fail over? Like it’ll drop to zero for a bit?
I don’t remember. Try at least 30-60 seconds on the right leg.