New powermeter rumours

Discuss light weight issues concerning road bikes & parts.
jepd1973
Posts: 39
Joined: Wed Mar 24, 2010 2:09 pm

by jepd1973

I have the P2M BOR688 crank.

I find it way more stiff than my SRAM S900 P2M - overall a great power meter. Changed from quarq to the P2M BOR and i think the switch has been great. I am not going back to quarq

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micky
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by micky

What differences did you notice?

by Weenie


jepd1973
Posts: 39
Joined: Wed Mar 24, 2010 2:09 pm

by jepd1973

I found that the quarq was a bit more "difficult" to use. Calibration would take a number of backpedals etc. (might not be the case with newer models). I also had calibration drift and the unit failed on me in a time trial (understating power with around 50w). So i sort of lost confidence in it after that.
The P2M seems like it is more fire and forget...and i haven't noticed any failures or anything on my two units..

silvercivic27
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Joined: Mon Jun 13, 2011 12:54 am

by silvercivic27

How did you determine "calibration drift" and your power being off by 50 W?

jepd1973
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Joined: Wed Mar 24, 2010 2:09 pm

by jepd1973

I know my FTP pretty well. I did a warm up on rollers before the TT. I warmed up by doing increased intensity up until i reached FTP. I did that a couple of times.
I then got of the rollers and did some rolling around before start.

I started the TT and within the first 5 minutes i almost blew up because i tried to dial in on my normal FTP. I actually tried to do the back spinning of the pedals to get i straightened out but no luck. After that i just focused on finding a good rhythm and i did not look at the power numbers. When i analyzed the file back home it was clear that the power meter had understated by approx 50w - well i could have been 40 watts. I sent the file to Quarq including the warmup and they replaced the power meter. I did some test with the ANT+ stick and the quarq app but no errors were found.

Calibration drift was determined by calibrating before and after a ride. I had some pretty large differences (don't remember the exact numbers)

rijndael
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by rijndael

FWIW: You'd need a Zero Offset drift of 136 points to show a 40w difference at 90 RPM, 170 points for 50w.

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Tinea Pedis
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by Tinea Pedis

jepd1973 wrote:I find it way more stiff than my SRAM S900 P2M

I hate to sound like one of 'those people' in relation to crank stiffness, but I do agree. I've found the s900 is not as stiff as it could be*.


*All depends of course on how many watts you produce/what you weigh.

jpanspac
Posts: 160
Joined: Thu Apr 11, 2013 8:21 pm

by jpanspac

jever98,

When will power2max start stocking the new Rotor 3d+ crank?
My favorite components are the ones I never have to think about.

jooo
Posts: 1510
Joined: Wed Feb 02, 2011 3:48 am

by jooo

Not sure if this has been mentioned in the thread yet (TL:DR yada yada), but this was posted recently: http://www.bikeradar.com/road/news/article/verve-cycling-teases-2014-power-meter-first-look-39319/
As well as the rings, the crank itself appears to be Praxis/Turn OEM type model designed to fit the PM units.

Image

aerozy
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by aerozy

Looks classy! Love to hear more about it! :beerchug:
Sunny cycling holidays in Portugal @ Cherry Cottage Vintage B&B

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prendrefeu
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by prendrefeu

Looks clean, which I appreciate.
It also seems a bit heavy.

Tangent, but relevant:
Can we get a comprehensive list of powermeter weights for comparison purposes?
This would be 'meter' weight:
-if crank-based: weight of sensor unit + both crank arms + spider, no chainrings, all variations.
-if hub-based: weight of hub
-if pedal-based: weight of sensor + pedals
-if shoe-based: weight of sensor + cleats

Comprehensive, meaning all variations within a brand?
Exp001 || Other projects in the works.

jever98
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Joined: Wed Feb 18, 2009 12:02 pm

by jever98

@prendrefeu: for power2max you can find the weights on the product pages on our site.

One comment - I think the additional weight is often the most relevant. For example, a sensor might be 180g, but the original spider 70g, making the net additional weight 110g. Same logic for hubs, pedals, etc.

Best
Nicolas from power2max
----
No longer in the industry

eric
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by eric

It can be difficult to figure additional weight for some power meters. For example the Sram/Quark meters are based on a model of Sram cranks which are not sold on their own without the power meter.

Further, it would be unlikely that someone with enough money to buy a PM would have been running one of those. Instead they would be coming from a Red or Force crank, which are lighter due to having an integrated carbon spider instead of a separate aluminium spider.

I think it's more useful to list the total weight of the PM (along with what "total" includes) as Prendrefeu suggests, and let people do the comparison to their current or proposed equipment.

jooo
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by jooo

prendrefeu wrote:It also seems a bit heavy.

IMO, not at all, if the claimed 'Sub-800g total unit weight' is right, then it's lighter than quite a few of the options on the market already.

eric wrote:For example the Sram/Quark meters are based on a model of Sram cranks which are not sold on their own without the power meter.

That's not really right. Sure there are lots of slightly different versions, but their removable spider cranks have been around for years, even being OEM spec on some bikes. The Force22 cranks is probably the most up to date example.

Dammit
Posts: 443
Joined: Sun Mar 27, 2011 8:16 pm

by Dammit

eric wrote:It can be difficult to figure additional weight for some power meters. For example the Sram/Quark meters are based on a model of Sram cranks which are not sold on their own without the power meter.

Further, it would be unlikely that someone with enough money to buy a PM would have been running one of those. Instead they would be coming from a Red or Force crank, which are lighter due to having an integrated carbon spider instead of a separate aluminium spider.

I think it's more useful to list the total weight of the PM (along with what "total" includes) as Prendrefeu suggests, and let people do the comparison to their current or proposed equipment.


Head unit, clamp, all magnets and sensors for an SRM:

Image

Standard spider:

Image

Powermeter:

Image

I make that 81 grams of additional weight for the powermeter, and 115 grams for the control gubbins- but that part is dependent on your setup of course, you could have a 910XT on your wrist etc etc.

by Weenie


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