Shimano R9100-P Powermeter

Discuss light weight issues concerning road bikes & parts.
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jay cee
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by jay cee

The new Shimano Powermeter gets looked at
https://youtu.be/okNpp5_E2-4
J EURO

djgarrett21
Posts: 40
Joined: Sun Mar 12, 2017 2:22 pm

by djgarrett21

Three things that disappoint:
- Cadence measured by magnet, not accelerometer.
- Claimed accuracy of +/-2%. Most other manufacturers are claiming +/-1.5% or even +/-1%. I know these numbers should be taken with a grain of salt but it is below what I would consider the industry standard. It will be interesting to see how the DA stacks up against others.
-Price for the power meter is an additional $1000. I was hoping they could come in quite a bit less given this is an OEM solution integrated into the crankset.

Generally Shimano puts out good product but for now I'm pretty underwhelmed by the power meter specs.

jeffy
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Joined: Sun Oct 05, 2014 11:51 pm

by jeffy

add to that list the "calibrate before every ride"

Mep
Posts: 275
Joined: Fri May 28, 2004 4:11 pm

by Mep

Count me in the camp of not impressed. I do think it's a step in the right direction of further commoditizing power meters, but as is typical a pretty mediocre first attempt.

BdaGhisallo
Posts: 1890
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

jeffy wrote:add to that list the "calibrate before every ride"


This is a feature to be appreciated and not a bug to be disappointed by.

jeffy
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by jeffy

BdaGhisallo wrote:
jeffy wrote:add to that list the "calibrate before every ride"


This is a feature to be appreciated and not a bug to be disappointed by.


meh i prefer the auto-calibration of P2M or back pedal by Quarq.

shonanmike
Posts: 38
Joined: Mon Nov 17, 2014 11:27 pm

by shonanmike

I doubt cadence is measured by magnet. GCN may be pulling this out of their ass.

Note that Pioneer uses a magnet to establish a datum for power vectors. Not necessary for power measurement only.


djgarrett21 wrote:Three things that disappoint:
- Cadence measured by magnet, not accelerometer.
- Claimed accuracy of +/-2%. Most other manufacturers are claiming +/-1.5% or even +/-1%. I know these numbers should be taken with a grain of salt but it is below what I would consider the industry standard. It will be interesting to see how the DA stacks up against others.
-Price for the power meter is an additional $1000. I was hoping they could come in quite a bit less given this is an OEM solution integrated into the crankset.

Generally Shimano puts out good product but for now I'm pretty underwhelmed by the power meter specs.

BdaGhisallo
Posts: 1890
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

shonanmike wrote:I doubt cadence is measured by magnet. GCN may be pulling this out of their ass.

Note that Pioneer uses a magnet to establish a datum for power vectors. Not necessary for power measurement only.


djgarrett21 wrote:Three things that disappoint:
- Cadence measured by magnet, not accelerometer.
- Claimed accuracy of +/-2%. Most other manufacturers are claiming +/-1.5% or even +/-1%. I know these numbers should be taken with a grain of salt but it is below what I would consider the industry standard. It will be interesting to see how the DA stacks up against others.
-Price for the power meter is an additional $1000. I was hoping they could come in quite a bit less given this is an OEM solution integrated into the crankset.

Generally Shimano puts out good product but for now I'm pretty underwhelmed by the power meter specs.


Well it wouldn't be the only PM to require a magnet to measure cadence. The SRM powermeters work like this.

rasmusic
Posts: 138
Joined: Fri Jul 10, 2009 1:48 am
Location: Norway

by rasmusic

Yeah, I bet the magnet is to measure cadence. I had the chance to inspect this power meter first hand on the bike of a Sunweb-rider last week, and he had the same magnet. But I can't see why a magnet is a downside.

Kurets
Posts: 141
Joined: Thu Feb 25, 2016 9:55 pm

by Kurets

Yeah, in which way does it matter that they use a magnet to measure cadence. The only downside is that it introduces an error with non round rings. Otherwise I'd actually prefer a magnet as it would be less sensitive to cobbles and rough roads where I sometimes have experienced wierd cadence readings from accelerometer based cadence sensors.
Pre ride calibration is also not a downside IMO, it gives the option for a very controlled calibration procedure.

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Calnago
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by Calnago

Accelerometers are subject to the issues @Kurets just mentioned.
But on the topic of pre ride calibration, I do it every ride, but I'm not sure exactly what it does. I run SRM power meters with a Garmin 1000 head unit. The calibration is done from the Garmin. Sorry this question isn't specific to the Shimano power meter but more of a general question relating to all power meters. Thanks in advance.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

BdaGhisallo
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by BdaGhisallo

The pre-ride calibration of a powermeter zeros the torque reading. The measured stress across the strain gauges will change minutely based upon the ambient temperature. Zeroing the PM accounts for this and ensures that all torque subsequently measured is due to the rider applying force to the pedal, and gives the rider a more accurate reading on the power they are producing.

pdlpsher1
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by pdlpsher1

jeffy wrote:
BdaGhisallo wrote:
jeffy wrote:add to that list the "calibrate before every ride"


This is a feature to be appreciated and not a bug to be disappointed by.


meh i prefer the auto-calibration of P2M or back pedal by Quarq.


On the Quarq do you backpedal before the ride? I always do the initial calibration from my Garmin 520. I wish there's a way to auto calibrate upon establishing the initial ANT+ connection. I'm always in a hurry to leave on a ride and I find it annoying to have to manually calibrate the ride by initiating a calibrate command from the Garmin. I would not think the backpedal calibration is accurate as the crank is not stationary.


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Calnago
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by Calnago

Thanks @BdaGhisallo, I knew it accounted for changes in ambient temperature from one ride to the next, but I wasn't quite sure what it was actually doing. Your explanation helps clarify that for me.
:beerchug:
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

BdaGhisallo
Posts: 1890
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

Calnago wrote:Thanks @BdaGhisallo, I knew it accounted for changes in ambient temperature from one ride to the next, but I wasn't quite sure what it was actually doing. Your explanation helps clarify that for me.
:beerchug:


My pleasure. This will add some more insight into the desirability of having to do the zero offset check before each session with a powermeter: https://powermetercity.com/2016/03/10/p ... ro-offset/

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