P2M L/R Power meter

Discuss light weight issues concerning road bikes & parts.
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MechMitch
Posts: 16
Joined: Fri Sep 07, 2018 2:10 am

by MechMitch

Can anone commet on the P2M L/R accuracy compoared to a real L/R power meter like vectors or infocranks

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Lewn777
Posts: 890
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Yes, a power 2 max and others like Quark 'chain ring spider' based PMs are usually more accurate than crank based power meters or pedal based power meters, in fact they are considered the gold standard. Fit, occasionally calibrate, and forget. They are positioned in the most logical place on a bike there is. I'm not sure what you are talking about with 'real' vs crank and pedal?

Crank based PMs and pedal based PMs can also get bashed around much more an can have a higher failure rate and often a lower inital cost also they can read a long way off accurate, but have the advantage they can be removed easily and swapped between bikes. The prices of spider based power meters has come down so much there is little point in buying anything else, and with some products you get free cranks with the PM so great if you are in the market for new cranks anyway. Of course that doesn't mean every spider based PM is automatically going to be better than anything else in every case.

A word of caution, there are lots of fanboys that will aggressively argue for the product that they've bought, usually owners of Stages crank based PMs and Garmin Vector or Assioma Favero pedals. There is nothing really wrong with these products other than I'd generally rather have a spider based PM like a P2M.

by Weenie


Papey
Posts: 22
Joined: Fri Mar 01, 2019 1:09 am

by Papey

Lewn777 wrote:
Mon Mar 25, 2019 12:13 am
Yes, a power 2 max and others like Quark 'chain ring spider' based PMs are usually more accurate than crank based power meters or pedal based power meters, in fact they are considered the gold standard. Fit, occasionally calibrate, and forget. They are positioned in the most logical place on a bike there is. I'm not sure what you are talking about with 'real' vs crank and pedal?

Crank based PMs and pedal based PMs can also get bashed around much more an can have a higher failure rate and often a lower inital cost also they can read a long way off accurate, but have the advantage they can be removed easily and swapped between bikes. The prices of spider based power meters has come down so much there is little point in buying anything else, and with some products you get free cranks with the PM so great if you are in the market for new cranks anyway. Of course that doesn't mean every spider based PM is automatically going to be better than anything else in every case.

A word of caution, there are lots of fanboys that will aggressively argue for the product that they've bought, usually owners of Stages crank based PMs and Garmin Vector or Assioma Favero pedals. There is nothing really wrong with these products other than I'd generally rather have a spider based PM like a P2M.
Dude you completely missed the question. p2m and all spider based PM estimate L/R balance based on where the spider is relative to the left/right crank. Dual leg powermeters individually measure the left and right separately.

I've got the p2m type S and it usually reads within 5% either way, ie 45/55 etc. When I do single leg pedaling it will read around 30/70 - whereas I'd image dual leg meters would read 0/100 in that instance. Interestingly, I can manipulate the balance when I use more hamstring to pull up, the other leg % will increase even though the power is being generated from the upstroke..You've probably already read up on the utility debate of L/R balance power, so if you want true L/R you'll need dual leg but if you want something to let you know an approximate balance then spider is fine.

AZR3
Posts: 825
Joined: Wed Sep 12, 2012 9:00 pm
Location: Az USA

by AZR3

I’ve owned 5 or 6 P2M and they are rock solid. I currently use Assioma DUOs for my road bike and a Quarq on gravel bike, both work faultlessly. As for which is better at L/R, only the Assioma, of the power meters I have used, gives a true L/R reading, the others use an algorithm to estimate L/R. So if true L/R is your goal you need pedal based or a spider/crank combo that measures both sides (pioneer/rotor2inpower etc)

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