New powermeter rumours

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handler
Posts: 99
Joined: Mon Aug 18, 2008 9:28 pm

by handler

Any news from SRM? The PC9 is really old by now

jever98
Posts: 1175
Joined: Wed Feb 18, 2009 12:02 pm
Location: Seattle

by jever98

I continue to be puzzled that so many people go for crank arm PMs. The design limitations vis-a-vis a spider PM are just so big: no auto zero, risk of damage, partial measurement or 2 units that can fail.
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by Weenie


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EvilEuro
Posts: 333
Joined: Fri Nov 13, 2009 10:03 am

by EvilEuro

jever98 wrote:
Sat Dec 03, 2022 12:57 am
I continue to be puzzled that so many people go for crank arm PMs. The design limitations vis-a-vis a spider PM are just so big: no auto zero, risk of damage, partial measurement or 2 units that can fail.
With the advent of quality pedal powermeters on Shimano SPD and SPD-SL, Look Keo, and Speedplay platforms, I'm unsure why someone would have a need or want to use a crank arm powermeter either. Is there a crank arm powermeter out right now working on carbon arms?

Irrespective of their prices, all of the pedal powermeters give the dual-sided power measurements that one would seemingly want from a crank arm PM. Favero, Garmin, SRM, and Speedplay, and with far fewer issues. They're also much easier to move than a crankset.

Favero has been crazy reliable from most accounts.

Garmin finally got their issues figured out with the Vector 3 / Rally pedals once they fixed the battery caps and folks moved from using 2x LR-44 batteries to a single CR1/3N battery. The fact that you can swap them between SPD, SPD-SL, and Look Keo pedals / cleats is an added bonus.

Speedplay finally has their PM pedals out for those who want that platform.

SRM has their X-Power PM pedals.

The only thing one could ask for is swapable pedal bodies from all of the manufacturers for more versatility. Oh, and for someone to get a powermeter into a Time pedal. That'd be nice too.

They all work well, they all track well, and none of them have the problems endemic to the Shimano crankarm problem. What's the reason for getting a crank arm powermeter again?

TobinHatesYou
Posts: 12458
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

All pedal power meters are designed to be power meters. Nearly all crankarm power meters are retrofits. The only exception is the Verve Infocrank.

And you can bet SRAM is developing a Time pedal power meter, but we may get an ATAC version before a XPro one.

Maddie
Posts: 1533
Joined: Tue Oct 17, 2017 5:44 am

by Maddie

jever98 wrote:
Sat Dec 03, 2022 12:57 am
I continue to be puzzled that so many people go for crank arm PMs. The design limitations vis-a-vis a spider PM are just so big: no auto zero, risk of damage, partial measurement or 2 units that can fail.
If you want to stay with SPD-SL, the only valid option right now is Garmin RS200. These cost nearly 3x as much as a Quarq Dfour DUB and the Quarq is known to be bulletproof as well.

TobinHatesYou
Posts: 12458
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Maddie wrote:
Sat Dec 03, 2022 9:40 am
jever98 wrote:
Sat Dec 03, 2022 12:57 am
I continue to be puzzled that so many people go for crank arm PMs. The design limitations vis-a-vis a spider PM are just so big: no auto zero, risk of damage, partial measurement or 2 units that can fail.
If you want to stay with SPD-SL, the only valid option right now is Garmin RS200. These cost nearly 3x as much as a Quarq Dfour DUB and the Quarq is known to be bulletproof as well.
My Quarqs are decent, but with caveats. I was seeing stretches of inaccuracy until MagicZero was turned off. It does not like being zeroed in cold conditions immediately after being taken outside. My Garmin pedals have no issues being zeroed after big temperature swings.

kervelo
Posts: 866
Joined: Wed Jan 21, 2009 6:58 am
Location: Finland

by kervelo

I have not noticed any issues with my Quarq in cold conditions. I have used the one on my mtb in -15 deg C temperatures and use it frequently in -5 deg C temperatures. However, the temperature in my bike shed is just 5-10 degs above zero, so the temperature change is not very big.

jever98
Posts: 1175
Joined: Wed Feb 18, 2009 12:02 pm
Location: Seattle

by jever98

Power2max have been bullet proof and affordable for years. Work with all pedals, too. :)
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EvilEuro
Posts: 333
Joined: Fri Nov 13, 2009 10:03 am

by EvilEuro

jever98 wrote:
Sat Dec 03, 2022 3:08 pm
Power2max have been bullet proof and affordable for years. Work with all pedals, too. :)
True, and I have used a P2M Campagnolo PM for years now with zero issues. I also have a set of Garmin Rally pedals and they track exactly in-line with my P2M. I don't use the Garmin anymore as I prefer Time pedals.

However, if you're married to a particular crankset and/or want dual-sided power measurements, pedals are the only way to go right now. That is unless you want only a Shimano crankset, in which case Stages now has a viable offering.

BigBoyND
Posts: 1350
Joined: Mon May 31, 2021 1:51 am
Location: Berlin, DE

by BigBoyND

If Assioma was using Look bodies, I'd probably get that. Assuming no q-factor changes.

I have two spider PMs (quarq and p2m) on my two bikes that cost roughly the same as one dual-sided pedal PM.

Downside is I like Speedplay on the TT bike and Look on my road bike.

Upside is pedal PM would allow me to bring it on vacations where I rent a bike or even on a hotel gym bike when biz trips interfere with training. And there would be guaranteed consistency across bikes.

RadB
Posts: 229
Joined: Mon Mar 02, 2020 3:24 am

by RadB

A single sided crank-base pm remains a robust and cheap gateway to a pm of adequate accuracy with the benefit of using all existing equipment and no additional required changes i.e. no extra chainrings, no changes to stackheights, no cutting an ISP, no new shoes or cleats to run a different pedal system of a different stack height (and possibly qfactor) which is not an insignificant consideration if you have an existing fleet of bikes you run regularly on expensive shoes.

TobinHatesYou
Posts: 12458
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RadB wrote:
Tue Dec 06, 2022 11:45 am
A single sided crank-base pm remains a robust and cheap gateway to a pm of adequate accuracy with the benefit of using all existing equipment and no additional required changes i.e. no extra chainrings, no changes to stackheights, no cutting an ISP, no new shoes or cleats to run a different pedal system of a different stack height (and possibly qfactor) which is not an insignificant consideration if you have an existing fleet of bikes you run regularly on expensive shoes.

ISP seatmast toppers have adjustability and if you haven't left breathing room for stack height changes, then u dun goofed. Even wearing a different pair of bib shorts, winter socks or changing shoes changes stack height without swapping pedals.

Adequate accuracy is a funny term. Something is either accurate or it isn't. A left-only power meter can only be accurate for someone who is only pedaling with one leg. If you have 50/50 average L/R balance, your average power during a ride will be close by coincidence...that doesn't mean the power meter is accurate. It is literally guessing half the time.

Additionally bonding strain gauges onto hardware not explicitly designed for the purpose has proven to be problematic. Infocrank has acknowledged this and specifically talks about how their bespoke power meter cranks are able to disregard non-rotational forces while many other power meters cannot. This is less of an issue with spiders and pedals, but it's a huge issue for flexy cranks that have bend so far away from the center of rotation.

maquisard
Posts: 3772
Joined: Thu May 01, 2008 8:51 pm
Location: France

by maquisard

TobinHatesYou wrote:
Tue Dec 06, 2022 11:57 am
Adequate accuracy is a funny term. Something is either accurate or it isn't. A left-only power meter can only be accurate for someone who is only pedaling with one leg. If you have 50/50 average L/R balance, your average power during a ride will be close by coincidence...that doesn't mean the power meter is accurate. It is literally guessing half the time.
You seem to be using accuracy when you mean precision.

Precision is much more important than accuracy for consistent training. So I don't think adequate accuracy is a funny term. If my powermeter reports 320W when I am doing 340W but it consistently reports 320W then it is precise and a useful training tool. In contrast, something that is accurate but not precise has no value in measuring training effort and load.

EvilEuro
Posts: 333
Joined: Fri Nov 13, 2009 10:03 am

by EvilEuro

TobinHatesYou wrote:
Sat Dec 03, 2022 8:41 am
All pedal power meters are designed to be power meters. Nearly all crankarm power meters are retrofits. The only exception is the Verve Infocrank.
I hadn't thought about the Verve Infocrank in ages until you bought it up in this reply. I had always been fascinated by them because they were providing dual-sided power measurements (accurately) from the crankarms, but their cost was always a bit prohibitive.

I went to their website just to see if anything had changed and it appears it has. Infocrank is getting ready to launch a new powermeter (the IC2) and is presently taking "early bird" orders at discounts of 15% off of the fist 100 orders, 10% off of the next round, and 5% off of the final round.

Notably though, the price on Infocrank's products has come down significantly. I recall them being $1600 for the crankset. They were still $1300 the last time I checked. The new IC2 has a base price of $990 USD and is presently $841.50 USD on preorder. That's a significant different.

Their original offering is also significantly discounted as they try to shift them out to make way for the IC2. Original Infocranks are now on sale at 50% off for $639.50 (down from $1279). That's a pretty good deal if Infocrank suits your needs.

Thanks for making me think of Infocrank again. Been a long time and it is nice to see what they're up to right now.

https://infocrank.cc/ic2
https://infocrank.cc/infocrank-ic2
infocrank.jpg

TobinHatesYou
Posts: 12458
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

maquisard wrote:
Tue Dec 06, 2022 2:38 pm
TobinHatesYou wrote:
Tue Dec 06, 2022 11:57 am
Adequate accuracy is a funny term. Something is either accurate or it isn't. A left-only power meter can only be accurate for someone who is only pedaling with one leg. If you have 50/50 average L/R balance, your average power during a ride will be close by coincidence...that doesn't mean the power meter is accurate. It is literally guessing half the time.
You seem to be using accuracy when you mean precision.

Precision is much more important than accuracy for consistent training. So I don't think adequate accuracy is a funny term. If my powermeter reports 320W when I am doing 340W but it consistently reports 320W then it is precise and a useful training tool. In contrast, something that is accurate but not precise has no value in measuring training effort and load.

No, I mean accuracy. When our power is bipedal a single leg measurement absolutely cannot be accurate (or precise.)

by Weenie


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