Power meters that support left/right power data

tricoachmike · October 9, 2011, 6:35pm

In the last few weeks we’ve seen Garmin formally announce their Vector, Brim Brothers showcase their pedal device, Rotor announce their power based cranks and probably a few others I’m missing. Unfortunately none of these are available today.

We also have Garmin who’s updated their firmware (or soon to upgrade?) to support left/right data on some existing watches. They also announced the 910XT which supports it out of the box.

Question is… what (ANT+ based) power meter device supports left right pedal data today? This is a harder question, but why doesn’t powertap offer any devices that send split left/right data like Computrainer? It won’t be a perfect solution since you’re not getting independent data, but the Computrainer is a real world example that the combined data can be filtered to get pretty good split data.

To pre-empt those questions “why do you need left right power, why not just get a powertap, etc, etc” I have chronic issues that are likely caused by overusing one leg vs the other… my right knee and hip routinely get injured, yet despite the injuries my right side is typically stronger when I do one-legged cycling drills… my best guess is that I have a very strong preference for my right side to the point I cause overuse injuries. The drills only go so far… I need the data for the 99% of the time I ride with both legs.

jackmott · October 9, 2011, 6:37pm

none of them

including the computrainer.

the computrainer is guessing, and it isn’t a good guess either.

the reason none of them do is it is expensive, and not very useful.

even the garmin setup isn’t going to let you see left/right power iirc. The average power is computed before being sent to the head unit right?

tevendale · October 9, 2011, 6:38pm

At the moment, only Polar’s power meters offer left and right measurements. And they’re not ANT+.

Regards

Stuart

tricoachmike · October 9, 2011, 6:52pm

none of them

including the computrainer.

the computrainer is guessing, and it isn’t a good guess either.

the reason none of them do is it is expensive, and not very useful.

even the garmin setup isn’t going to let you see left/right power iirc. The average power is computed before being sent to the head unit right?

Do you have data to show that the computrainer is inaccurate? guess is a very strong word.

As for your comment where you said it’s not very useful see my opening post.

Re: garmin setup… check the 910XT and the vector. Vector calculates it independently and the 910XT records it independently. Power is both calculated independently and recorded independently. Are you saying they add extra steps to average it together then unaverage it? That doesn’t make sense.

tricoachmike · October 9, 2011, 6:56pm

Yeah familiar with Polar. Besides the ANT+ problem, there is no published research testing the validity and reliability of the chain-based device (pubmed yields no results) … plus it’s on the deprecation path with their new LOOK pedal too.

tevendale · October 9, 2011, 7:06pm

Was a bit of a pain to set up as well. I’ve since moved to PowerTap, but I did find the Polar was reasonably accurate compared with the PowerTap.

Regards

Stuart

styrrell · October 9, 2011, 7:16pm

Today, I think only a few older stationary cycles. USCF had some or had access way back when. The very first on bike PM I every saw in person had that capability but it was a one off made by Frank Fedel in Detroit and I don’t think he ever made another.

dcrainmaker · October 9, 2011, 8:34pm

…
even the garmin setup isn’t going to let you see left/right power iirc. The average power is computed before being sent to the head unit right?

The ANT+ protocal for Left/Right power calls for the transmitter to send the percentage (%) value of total power of the right leg, to the head unit - in addition to total power (watts). This allows a head unit to then calculate:

Total Power (watts)
Left Power (Watts)
Right Power (Watts)
Left Power (percentage)
Right power (percentage)

There’s also talk by both Barry Redmond (Brim Brothers) and Clark Foy (Garmin Vector team) about extending the ANT+ power meter device profile to then do more around left/right power with respect to where the pressure is coming from, and thus aim towards the fit side of things. There’s zero doubt in my mind we’ll see this, likely by next summer. The good news is all the players are talking together on this, so we’ll see a cohesive solution here.

To see how this looks, see this post here, under head units:

http://www.dcrainmaker.com/2011/09/everything-you-ever-wanted-to-know.html

As noted earlier, the Edge 800 should get it any day now, and then after that the 500 and then 310XT. The 910XT will get it pre-release. I asked the Timex guys about this, and they said once products are out there, they’ll look at doing something to the TGT, but made no promises. The CycleOps guys also said that they expect to eventually support Left/Right power once it’s out there.

But for power meters that do it today, all except the Polar/Look Keo Power System and CT are pre-release. Those coming with seperated left power are (all below ANT+):

A) Garmin Vector - March 2012
B) Brim Brothers Zone - TBD, but likely 2012
C) O-Synce - TBD
D) Rotor System - TBD, maybe 2012, maybe 2013

I’ve seen in person the Vector and Zone demonstrating it (and of course the Polar units).

Ok…more than you probably wanted to know…

styrrell · October 9, 2011, 8:48pm

Kinda off topic but has the Edge 200 bike computer been released yet and have you tried it?

dcrainmaker · October 9, 2011, 8:52pm

Kinda off topic but has the Edge 200 bike computer been released yet and have you tried it?

http://www.dcrainmaker.com/2011/08/garmin-edge-200-in-depth-review.html

Short version: If it’s for you as a ST’er, spend $50 extra and find the Edge 500 on sale. If it’s for your parents going out for a nice easy ride, go Edge 200 with an REI coupon.

tricoachmike · October 9, 2011, 10:23pm

Ray - this is the kind of in depth response I was looking for.

Jack & Ray - Regarding the way ANT+ sends the data, I bet this decision was made in order to maintain some sort of backwards compatibility and reduce the number of new fields needed and to reduce storage requirements. Clever. Mathematically it’s equivalent to sending L and R power separately… 6th grade linear algebra.

What about SRM or Quarq? I would expect them to be logical choices as their products are already out… but I don’t see anything on their website.

Thanks for the heads up on the cycleops… good to hear they’re at least thinking about it. I’ll hold off a little until maybe Garmin releases the new firmware and see if Cycleops responds.

dcrainmaker · October 10, 2011, 12:38am

RE: ANT+ Decision
Backwards compatibility is maintained by still sending total power. However, L/R power will/does require an update to all current head units - none support it today (except test firmware releases for the Edge 800 and a few custom Android apps).

RE: SRM, CycleOps, Quarq, etc
Every power company is looking at how Left/Right power can be incorporated in their future products. Whether or not it ends up being super-useful from a training standpoint is of less a concern to power companies, since they know folks will ultimately ask for it. However, I can say don’t wait around for a new left/right power meter for CycleOps, it won’t be happening anytime soon. If we’re talking head units - then sure, no harm there since they’ve essentially got until at least March to get the firmware updated.

jsoderman · October 10, 2011, 1:24pm

Hey DC,
bit of a hijack, but any word on when the new powertap hubs and computers are going to be released?

Former_User · October 10, 2011, 1:42pm

Was a bit of a pain to set up as well. I’ve since moved to PowerTap, but I did find the Polar was reasonably accurate compared with the PowerTap.

I found it was VERY accurate for durations longer than 1-2 minutes (shorter durations get “clipped” due to the recording scheme, especially the older models that only supporst 5s sampling rate).

http://forum.slowtwitch.com/gforum.cgi?post=1740742;search_string=polar%20pt;#1740742

Nicko · October 10, 2011, 7:16pm

Question is… what (ANT+ based) power meter device supports left right pedal data today?
If you want to do this today, there is only one option.
Ergomo+another PM.

“Calibrate” the Ergomo by doing left leg only pedaling, in a controlled environment. Half the Ergomo “watts” should equal the watts from the other PM.
Deduce a formula that transforms Ergomo “watts” to real, left leg watts.

When riding for real, somehow merge the data from both meters, export to e.g. Excel, and extract left&right “real” power, not some guesstimated pulse-height-comparison. Tada! (Aren’t you glad you asked?)

tricoachmike · October 10, 2011, 7:41pm

Question is… what (ANT+ based) power meter device supports left right pedal data today?
If you want to do this today, there is only one option.
Ergomo+another PM.

“Calibrate” the Ergomo by doing left leg only pedaling, in a controlled environment. Half the Ergomo “watts” should equal the watts from the other PM.
Deduce a formula that transforms Ergomo “watts” to real, left leg watts.

When riding for real, somehow merge the data from both meters, export to e.g. Excel, and extract left&right “real” power, not some guesstimated pulse-height-comparison. Tada! (Aren’t you glad you asked?)

Either I don’t understand how the Ergomo works or I don’t follow. It sounds like this would be prone to the same kind of data filtering errors and would require some extra manual steps for excel manipulations – the kind of manual steps I would likely not perform long term This would only work if the Ergomo could be calibrated to completely ignore any data from the right leg. Since the strain gauges are in the BB and not the crank arm I don’t think it’s possible to separate the data like that without doing some data filtering on the single power curve (with cadence data) similar to what Computrainer does.

tricoachmike · October 10, 2011, 7:57pm

RE: SRM, CycleOps, Quarq, etc
Every power company is looking at how Left/Right power can be incorporated in their future products. Whether or not it ends up being super-useful from a training standpoint is of less a concern to power companies, since they know folks will ultimately ask for it. However, I can say don’t wait around for a new left/right power meter for CycleOps, it won’t be happening anytime soon. If we’re talking head units - then sure, no harm there since they’ve essentially got until at least March to get the firmware updated.

Re: usefulness. I think it will depend on the user and what they’re trying to do with it. For some it will surely be the coolness factor and if that’s what it takes for me to get the feature I can actually use, then so be it As I was telling a friend… power without left/right leg data is not as useful to me.

Re: dates. I don’t follow. Above you said “As noted earlier, the Edge 800 should get it any day now, and then after that the 500 and then 310XT. The 910XT will get it pre-release.” So the firmware should come out at latest before Nov 15th (910XT release date). I’ll use look around a few days +/- release date to see if anyone’s else has announced a new power meter or power meter firmware. I’d wait around for the Vector (march isn’t bad) except I’m a speedplay user and don’t feel like downgrading to a lesser pedal. (now watch this thread turn into a pedal war)

dcrainmaker · October 10, 2011, 8:02pm

RE: SRM, CycleOps, Quarq, etc
Every power company is looking at how Left/Right power can be incorporated in their future products. Whether or not it ends up being super-useful from a training standpoint is of less a concern to power companies, since they know folks will ultimately ask for it. However, I can say don’t wait around for a new left/right power meter for CycleOps, it won’t be happening anytime soon. If we’re talking head units - then sure, no harm there since they’ve essentially got until at least March to get the firmware updated.

Re: usefulness. I think it will depend on the user and what they’re trying to do with it. For some it will surely be the coolness factor and if that’s what it takes for me to get the feature I can actually use, then so be it As I was telling a friend… power without left/right leg data is not as useful to me.

Re: dates. I don’t follow. Above you said “As noted earlier, the Edge 800 should get it any day now, and then after that the 500 and then 310XT. The 910XT will get it pre-release.” So the firmware should come out at latest before Nov 15th (910XT release date). I’ll use look around a few days +/- release date to see if anyone’s else has announced a new power meter or power meter firmware. I’d wait around for the Vector (march isn’t bad) except I’m a speedplay user and don’t feel like downgrading to a lesser pedal. (now watch this thread turn into a pedal war)

Just to ensure we’re fully on the same page here - the 500/800/310XT/910XT getting Left/Right power data won’t actually display Left/Right power unless you have a compatible ANT+ Left/Right power capable power meter. Of which, none exist today. The soonest will be Vector in March 2012.

tricoachmike · October 10, 2011, 8:04pm

RE: SRM, CycleOps, Quarq, etc
Every power company is looking at how Left/Right power can be incorporated in their future products. Whether or not it ends up being super-useful from a training standpoint is of less a concern to power companies, since they know folks will ultimately ask for it. However, I can say don’t wait around for a new left/right power meter for CycleOps, it won’t be happening anytime soon. If we’re talking head units - then sure, no harm there since they’ve essentially got until at least March to get the firmware updated.

Re: usefulness. I think it will depend on the user and what they’re trying to do with it. For some it will surely be the coolness factor and if that’s what it takes for me to get the feature I can actually use, then so be it As I was telling a friend… power without left/right leg data is not as useful to me.

Re: dates. I don’t follow. Above you said “As noted earlier, the Edge 800 should get it any day now, and then after that the 500 and then 310XT. The 910XT will get it pre-release.” So the firmware should come out at latest before Nov 15th (910XT release date). I’ll use look around a few days +/- release date to see if anyone’s else has announced a new power meter or power meter firmware. I’d wait around for the Vector (march isn’t bad) except I’m a speedplay user and don’t feel like downgrading to a lesser pedal. (now watch this thread turn into a pedal war)

Just to ensure we’re fully on the same page here - the 500/800/310XT/910XT getting Left/Right power data won’t actually display Left/Right power unless you have a compatible ANT+ Left/Right power capable power meter. Of which, none exist today. The soonest will be Vector in March 2012.

We’re definitely on the same page. I’m just wondering if any of the other manufacturers are timing their new products around the new firmware release date.

Nicko · October 10, 2011, 8:06pm

The Ergomo only measures torque from the left crank arm. The measured data is doubled before it is displayed/saved.