Shimano R9100-P Powermeter

Discuss light weight issues concerning road bikes & parts.
mds
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by mds

PinaF8 wrote:Oddly, I don’t have those spikes when paired to SRM 9000 powermeter.

Up thread there is a report of PC8 spiking on a Tacx Neo trainer. Maybe it is a third-party ANT+ PM issue? Or maybe just broken units?
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PinaF8
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by PinaF8

mds wrote:
PinaF8 wrote:Oddly, I don’t have those spikes when paired to SRM 9000 powermeter.

Up thread there is a report of PC8 spiking on a Tacx Neo trainer. Maybe it is a third-party ANT+ PM issue? Or maybe just broken units?


My pioneer and Neo does show spikes. However I can recreate it when my legs are not smooth.
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ms6073
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by ms6073

PinaF8 wrote:My pioneer and Neo does show spikes. However I can recreate it when my legs are not smooth.

While not directly related to the thread title, with the design of the Neo and how it applies resistance, it will amplify the slightest deviations in cadence, resulting in very stochastic resistance curves until the cadence issues are resolved. That is why some Neo users report uneven/non-smooth resistance values, regardless of cadence, if you are pedaling 'squares', the Neo is going to produce resistance directly proportionate to the cadence that is being input.
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mds
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Joined: Sat Dec 13, 2008 6:28 pm
Location: California

by mds

charmette1261 wrote:There is advantage or inconvenient to use PC8 with 9100P compared to an Garmin unit ?
I have a PC8.

I forgot to mention: PC8 neither displays nor logs R9100-P "Pedal smoothness", "Torque efficiency", and "Battery level information". I believe newer Garmins support the first two, I am not sure about the latter.
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mds
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Location: California

by mds

I wanted to see how the PC8 power spikes on the R9100-P affect my ride statistics.

So I wrote a javascript to detect and remove the spikes from activity .fit files, while leaving the rest of the data unmodified. Each spike is replaced by the 5s median power.

NP and TSS on my segments and rides go down by 1 or 2 watts/TSS.

The chart shows example of an 8 minute climb segment, with the original and despiked data.
Attachments
Despike.png
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pantelones
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Joined: Mon Jan 31, 2011 2:24 am

by pantelones

mds wrote:I wanted to see how the PC8 power spikes on the R9100-P affect my ride statistics.

So I wrote a javascript to detect and remove the spikes from activity .fit files, while leaving the rest of the data unmodified. Each spike is replaced by the 5s median power.

NP and TSS on my segments and rides go down by 1 or 2 watts/TSS.

The chart shows example of an 8 minute climb segment, with the original and despiked data.


Have you filed a report to SRM?

The following forum is related to SRM PC8 and associated firmware development.
http://www.srmservice.com/forum/viewforum.php?f=2

mds
Posts: 199
Joined: Sat Dec 13, 2008 6:28 pm
Location: California

by mds

pantelones wrote:Have you filed a report to SRM?

The following forum is related to SRM PC8 and associated firmware development.
http://www.srmservice.com/forum/viewforum.php?f=2

Yes. SRM says

"If the PC8 would cause this issue, we would have Power Spikes with all systems transmitting read calculated Power. ... Its more likely that something is rolling over in the DA PowerMeter at a continuous interval, but I could only tell for sure if I could examine the ANT+ Data that is transmitted by the PowerMeter. The PC8 does not do any filtering of the received data, because its ready calculated and should be correct."

Shimano asked me to update R9100-P firmware, which I did, to no improvement.

I am still investigating and soon will be trying different equipment parings (eg PC8/power2Max, Wahoo Bolt/R9100-P, E-TUBE app/R9100-P).
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petal666
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by petal666

mds wrote:
It could be the problems are specific to my units. I am still investigating.
The GPS inaccuracy is across all PC8s. It's GPS implementation is rubbish.

BdaGhisallo
Posts: 1927
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

petal666 wrote:
mds wrote:
It could be the problems are specific to my units. I am still investigating.
The GPS inaccuracy is across all PC8s. It's GPS implementation is rubbish.


I have to agree with you there. As much as I love SRM for power measuring and recording, their GPS capabilities suck. When I first got my PC8 and gave the GPS a try, it would take up to 20 mins to lock onto a satellite and get a fix. This is in the same exact spot where my wife's cheapo Garmin running watch locks in a satellite in mere seconds.

I am not that bothered by it though, as GPS isn't something I ever wanted. I have never Strava'd and I have no desire to record my routes. I basically wanted the reliability and robustness of the PC7 with some added fields and the ability to customize them and a better display, and I got everything I wanted with the PC8.

mds
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Location: California

by mds

BdaGhisallo wrote:I basically wanted the reliability and robustness of the PC7 with some added fields and the ability to customize them and a better display, and I got everything I wanted with the PC8.

How is your PC8 screen contrast during sunny mornings and afternoons?

In these conditions with sunglasses I find that my is PC8 a bit hard to read (eg low contrast). I actually think my PC7 had higher contrast.
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BdaGhisallo
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by BdaGhisallo

mds wrote:
BdaGhisallo wrote:I basically wanted the reliability and robustness of the PC7 with some added fields and the ability to customize them and a better display, and I got everything I wanted with the PC8.

How is your PC8 screen contrast during sunny mornings and afternoons?

In these conditions with sunglasses I find that my is PC8 a bit hard to read (eg low contrast). I actually think my PC7 had higher contrast.


I don't have any problems reading the screen at any time, no matter the ambient brightness.

mds
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Location: California

by mds

BdaGhisallo wrote:
mds wrote:I don't have any problems reading the screen at any time, no matter the ambient brightness.

Here is a photo of my PC8 in morning light, along with a Garmin 500 and iPhone 7.

Do you think the PC8 screen is working correctly?

I need more contrast, especially with sunglasses.
Attachments
PC8contrast.jpg
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charmette1261
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by charmette1261

mds wrote:
BdaGhisallo wrote:
mds wrote:I don't have any problems reading the screen at any time, no matter the ambient brightness.

Here is a photo of my PC8 in morning light, along with a Garmin 500 and iPhone 7.

Do you think the PC8 screen is working correctly?

I need more contrast, especially with sunglasses.


take garmin 520 or 1000 you can't ride with it :mrgreen: :mrgreen:

BdaGhisallo
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by BdaGhisallo

mds wrote:
BdaGhisallo wrote:
mds wrote:I don't have any problems reading the screen at any time, no matter the ambient brightness.

Here is a photo of my PC8 in morning light, along with a Garmin 500 and iPhone 7.

Do you think the PC8 screen is working correctly?

I need more contrast, especially with sunglasses.


That looks a little blue-ish. I wonder if, somehow, the back-light is on.


mds
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Location: California

by mds

BdaGhisallo wrote:That looks a little blue-ish. I wonder if, somehow, the back-light is on.

Yes, thank you. I turned Auto Backlight off. Contrast is better in morning sunshine now, and also fine later in the morning as well as in the shade.

Regarding my PC8/R9100-P power spike issue: On my trainer I tested R9100-P with Shimano's E-Tube app (with BLE connection, not ANT+) on iPhone 7 Plus. No power spikes. I previously mentioned Garmin 500 ANT+ shows no spikes, but the Garmin appears to be filtering the data, so I don't think I can conclude anything.

I rode again today, PC8/R9100-P data continues to look great (except for the spikes which I remove now with my script before analysis). In fact, the data looks in general better than my old PC7/SRM7900 setup, which I bought new 6 years ago, R9100-P is significantly less noisy.

I switched from summer to winter tires on my previous ride. I am pleased to see that the winter tire's additional rolling resistance is obvious and consistent across 7 hours of R9100-P data. While holding nearly the same average power, my climbs are taking slightly longer, a result consistent with a few more watts of rolling resistance.
Last edited by mds on Mon Nov 20, 2017 3:16 am, edited 1 time in total.
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