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PostPosted: Sat Nov 11, 2017 2:09 am 
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Location: Melbourne, Victoria, Australia
mds wrote:
Conza wrote:
Awesome. Love to hear your thoughts over time. I'll be looking in mid-Jan for a PM.

First ride yesterday with the R9100-P powermeter and PC8 head. 26km of rollers with one 480m ascent at 7% grade.

Power and cadence data appears consistent with both my expectations and my SRM powermeter history. Both the R9100-P and PC8 are working well.

The first plot shows a ~7 minute section on the climb from the SRMX analysis app. I was trying to ride about 230w, you can see what I think are typical variations in power. Cadence and speed track each other as expected (no gear changes).

I also downloaded the ride to Strava, I have not been able to do this previously with my SRM PC7. The second plot shows the same ~7 minute section. The scales are different. You can see an anomaly on the power plot, a "spike" of about 330w occurs roughly every minute. These spikes do not appear in the SRMX plot, power is always well below 315w. I submitted a trouble ticket to Strava concerning this issue. Alternatively, it could be a SRM app downloading to Stava issue so I will also ask SRM tech support.


Legend, thanks for letting strava know. I am big on that integration / support being accurate / correct.

Hopefully it gets sorted / let me know their response. :beerchug:

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Posted: Sat Nov 11, 2017 2:09 am 


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PostPosted: Sat Nov 11, 2017 3:33 am 
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Posts: 177
Location: California
cunn1n9 wrote:
If you have a look at the Shimano docs on this what you will find is that it works similar to other dual sided PM’s (eg Vector or Powertap p1 etc) but with one important difference. With most dual sided PMs one crank or pedal is the slave (usually the left side) and it transmits to the master (usually the right side). This is then combined and sent as a single data stream to the head unit that will have the following day items in it: total power, Power balance l/r, torque effectiveness l/r. Shimano has direct linked via a wire the two sides together so it eliminates one wireless transmission thus making it less likely to have errors (eg my old vectors use to loose the L side sometimes). On the Shimano the L and R data for the above data items are combined and sent as a single stream. If your srm head unit can display l/r balance and l/r torque effectiveness then you should get that data. I never look at it while riding.

I just upgraded to the Shimano from Stages so that I would have the complete picture of my power rather than the assumption of L=R. I am actually 48/52 according to the Shimano (overall ride average). Thing I notice from the Shimano is very stable cadence due to magnet that works down to very low cadence. The Stages was flaky below 32 rpm due to its sample rate (64 samples/sec). If you understand the maths behind this you will know why 32 is the limit for the Stages.

I also see much faster pickup of power changes on the Shimano also and I would think this is due to much more accurate cadence detection.


DM says R9100-P streams

- Power
- Cadence
- Left/right power balance
- Pedal smoothness
- Torque efficiency
- Battery level information

PC8 displays and logs the first three, not sure about the rest.

I see average 53/47% balance on my first ride.

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PostPosted: Sat Nov 11, 2017 1:07 pm 
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Joined: Sun Mar 12, 2006 8:25 pm
Posts: 194
Location: Israel
mds wrote:
cunn1n9 wrote:
If you have a look at the Shimano docs on this what you will find is that it works similar to other dual sided PM’s (eg Vector or Powertap p1 etc) but with one important difference. With most dual sided PMs one crank or pedal is the slave (usually the left side) and it transmits to the master (usually the right side). This is then combined and sent as a single data stream to the head unit that will have the following day items in it: total power, Power balance l/r, torque effectiveness l/r. Shimano has direct linked via a wire the two sides together so it eliminates one wireless transmission thus making it less likely to have errors (eg my old vectors use to loose the L side sometimes). On the Shimano the L and R data for the above data items are combined and sent as a single stream. If your srm head unit can display l/r balance and l/r torque effectiveness then you should get that data. I never look at it while riding.

I just upgraded to the Shimano from Stages so that I would have the complete picture of my power rather than the assumption of L=R. I am actually 48/52 according to the Shimano (overall ride average). Thing I notice from the Shimano is very stable cadence due to magnet that works down to very low cadence. The Stages was flaky below 32 rpm due to its sample rate (64 samples/sec). If you understand the maths behind this you will know why 32 is the limit for the Stages.

I also see much faster pickup of power changes on the Shimano also and I would think this is due to much more accurate cadence detection.


DM says R9100-P streams

- Power
- Cadence
- Left/right power balance
- Pedal smoothness
- Torque efficiency
- Battery level information

PC8 displays and logs the first three, not sure about the rest.

I see average 53/47% balance on my first ride.


All the Dual-Leg Powermeters when using ANT+ "Standard Protocol" will have just one unit streaming data using ANT+, when using Pioneer, you pair the left sensor to the right sensor and the right sensor is the one sending the data using ANT+, this is exactly what Shimano does, the difference in Pioneer is that when using their Protocol, they are able to send two different streams to their computer, these, you have two independent sensors.
To clarify it, when using the "Pedaling Monitor" mode in Pioneer, you will see two units (Left and Right) in their computer, when using "Dual ANT Power" mode you will see just one unit and when using "Single ANT Power" you will see two units but each of them is actually just doubling (unless you changed it when switching the mode) the data (i.e: one legged power meter).
I'm not sure how Garmin does it, but i can assume the same.


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PostPosted: Sat Nov 11, 2017 3:29 pm 
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Posts: 1166
Ant+ is ant+. However the PM calculates it under the hood doesn't matter, it's still transmitting the same coded data. Power, cadence, lr balance are all standard fields now. Pedal smoothness and torque efficiency are likely custom fields that are dependent on the computer and PM matching.... Buuuuuut garmin just opened up the cycling dynamics spec, so maybe someday in the near future that won't be the case.


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PostPosted: Sat Nov 11, 2017 5:32 pm 
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Joined: Mon Oct 15, 2007 9:28 pm
Posts: 1371
All this negative talk about the Origin SRM crankarms- Does anyone have personal knowledge from using an Origin SRM?


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PostPosted: Sat Nov 11, 2017 6:47 pm 
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Yep - the origin has been fantastic albeit I didn't expect to see a difference over my previous DA9000 other than weight. Honestly feels more like the s-works\cdale SRM options in terms of weight\stiffness (subjective-ish ...) with the addition of the tri-lobe though which is a nice benefit. AG2R has not had any long term issues with trilobe yet either so ill assume this is a good addition.

I haven't posted any photos or weights but took them as people seem to be curious online. I will post something over to one of the SRM threads so as not to hijack this one :)

Glad the R9100 is now available to folks looking to keep the look of Dura Ace as well as having another power option out there. Literally something out there for everyone at the moment.

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PostPosted: Sun Nov 12, 2017 2:16 am 
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Posts: 177
Location: California
Conza wrote:
Legend, thanks for letting strava know. I am big on that integration / support being accurate / correct.
Hopefully it gets sorted / let me know their response.

Strava got back. The spikes are in the data. I had not seen them in other apps due to smoothing, turn smoothing off and they appear. So the problem is not with Strava.

Today on a 3 hour ride I now see the spikes on the head unit that I had not previously noticed. I found I needed to watch the head closely to see them, as they appear and disappear quickly. They occur repeatedly, usually once every 60 to 65 seconds. Could be a head unit problem. I am investigating, I will try a different head.

The attached plot shows the spikes in SRMX with smoothing off. You can see the repeating period well. The highest spike is nearly 500w.


Attachments:
SRMX Power Spikes.jpg
SRMX Power Spikes.jpg [ 7.42 KiB | Viewed 546 times ]

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PostPosted: Sun Nov 12, 2017 5:55 pm 
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Location: California
power2max.com gives a power meter accuracy test procedure here. Open the Accuracy section and scroll to the bottom of the page.

The procedure compares the average power on a climb to a calculated estimate. The two should be within +/- 10 watts.

Yesterday I did three climbs with my R9100-P, here are the results:

Distance (km), Ascent (m), R9100-P average (w), Total power (due to 98% efficiency) (w)
6.93, 492, 226, 223
3.83, 288, 228, 225
4.05, 256, 213, 210

The differences are all within +/- 10 watts.

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PostPosted: Sun Nov 12, 2017 6:02 pm 
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Location: France
exist an app for Shimano 9100 P ?
the computer garmin allows it to use more data than the pc8(have it) ? smoothness torque efficiency ....

Thanks


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PostPosted: Sun Nov 12, 2017 10:26 pm 
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Posts: 177
Location: California
Has anyone been able to connect R9100-P via bluetooth to Stava iPhone app as a power sensor? So far I can't.

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PostPosted: Mon Nov 13, 2017 12:36 am 
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Location: Sutton, MA USA
It can't connect via bluetooth as a sensor. Only to the etube app for firmware updates.


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PostPosted: Mon Nov 13, 2017 5:37 pm 
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Joined: Fri Aug 12, 2016 9:20 am
Posts: 6
has anyone managed to secure a delivery the power meter with 170mm cranks. Ive been waiting since April and now was told today by there lbs that the delivery date is another month away. Hardly a major issue as its winter now for me but how can you tell someone on the day of delivery that its another month away.


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PostPosted: Mon Nov 13, 2017 9:58 pm 
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Posts: 177
Location: California
Re: my R9100-P power spike investigation

I did a short ride with both SRM PC8 and Garmin 500 heads, and compared the recorded data.

Here is a plot of a 3 minute segment. The power spikes appear only on the SRM. Spikes occur every ~64 seconds. The non-spike areas are close but not identical.

The second plot is cadence on the same segment. Again close but not identical.

My conclusion (now): It is possible that the R9100-P is spiking and the Garmin is successfully removing the spikes. But IMO the absence of spikes is so clean that I find this unlikely. IMO the problem is more likely SRM head.

I will try to borrow a Wahoo and try that next.

Also: so far, across my rides, the presence of the spikes increases average power on climbs by about 0.7% (eg by about 1.5w at 225w).


Attachments:
PowerChart.png
PowerChart.png [ 5.8 KiB | Viewed 271 times ]
CadenceChart.png
CadenceChart.png [ 5.75 KiB | Viewed 271 times ]

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PostPosted: Mon Nov 13, 2017 10:37 pm 
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I also have spikes when I pair my pc8 to my Tacx Neo trainer. Not too worried about it as it never affect my avg during interval trainings.

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Posted: Mon Nov 13, 2017 10:37 pm 


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PostPosted: Mon Nov 13, 2017 10:42 pm 
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Location: California
PinaF8 wrote:
I also have spikes when I pair my pc8 to my Tacx Neo trainer. Not too worried about it as it never affect my avg during interval trainings.

Thank you, it is helpful to have an independent observation.

Yes I agree negligible impact on avg.

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