Quote on power meters

tunney

ST: There is this thought that how one meter compares to the next is not important, as long as it is constant with output.

Ray: I would say that is an easy trap to fall into. Because once that power meter reaches the end of its useful life, whether that is 1, 2, 4 or 10 years from now, then how do you compare your historical gains to the next power meter that you buy? So you want it to be accurate, because if you are going to be in the sport long term, you want to be able to compare your growth and history over time. And you can’t do that, if you don’t have things that are not going to match.

Coming off the back of the thread over on "Fat Lads on Bikes", this is important. I've ten years of data to compare against. Cannot do that with some of the new entrants.

pgibbo

That's a very good point. Obviously SRM is the gold standard. What would be your recommendations thereafter? Cheers.

tunney

pgibbo wrote: »

That's a very good point. Obviously SRM is the gold standard. What would be your recommendations thereafter? Cheers.

Quarq seem decent, P2M newer models.

Powertap have alot of build problems and you lose 3-5% to drivetrain so direct comparisons to other PMs over time not as nice.

Polar Pedals and Garmin Vectors are having some data quality issues.

Stages.......... left side only.

Cannot see Brimm working.

No other players actually on the market as far as I can remember.

However the BIG thing is being able to verify and update the calibration of your unit.

A 4 year old P2M, does 200 watts still mean 200 watts? How can you tell and if an issue what can you do?

BennyMul

without wanting to reopen that thread and the fun reading some of the responses.

are you comparing like for like, you cannot | should not compare SRM & Stages.
they are aimed at a different demographic.

My question is do the people who purchase a stages pm, want to compare data over 10 years, I would say no and be surprised if many of them were still cycling in 10years.
So is the use of these PM valid for the purpose, to provide some sort of guidance to their training (even if the value is not always linear).

ray o

tunney wrote: »

A 4 year old P2M, does 200 watts still mean 200 watts? How can you tell and if an issue what can you do?

Can you calibrate P2M or Quarq yourself as you would with an SRM?

sconhome

tunney wrote: »

Polar Pedals and Garmin Vectors are having some data quality issues.

Link to these spurious claims?

My data has been fine, its the quality of headunit which has been the issue. Once the data exported to GC or TP it's easy to analyse.

tunney

ray o wrote: »

Can you calibrate P2M or Quarq yourself as you would with an SRM?

No idea.

AKW wrote: »

Link to these spurious claims?

My data has been fine, its the quality of headunit which has been the issue. Once the data exported to GC or TP it's easy to analyse.

Copy and paste from an email.........

Abstract

Powermeters have traditionally been integrated into the crankset but several manufacturers have designed new systems located elsewhere on the bike such as inside the pedals.
PURPOSE: This study aimed to determine the validity and reliability of the Keo power pedals during several laboratory cycling tasks.
METHODS: Ten active male participants (mean ± SD age 34.0 ± 10.6 y, height 1.77 ± 0.04 m, body mass 76.5 ± 10.7 kg), familiar with laboratory cycling protocols completed this study. Each participant was required to complete two laboratory cycling trials on an SRM ergometer (SRM, Germany) which was also fitted with the Keo power pedals (Look, France). The trials consisted of an incremental test to exhaustion followed by 10 min rest and then three 10 s sprint tests separated by 3 min of cycling at 100 W.
RESULTS: Over power ranges of 75-1147 W the Keo power pedal system produced typical error (TE) values of 0.40, 0.21 and 0.21 for the incremental, sprint and combined trials respectively, compared to the SRM. Mean differences of 21.0 W and 18.6 W were observed between trials 1 and 2 with the Keo system in the incremental and combined protocols respectively. In contrast the SRM produced differences of 1.3 W and 0.6 W for the same protocols respectively.
CONCLUSIONS: The power data from the Keo power pedals should be treated with some caution given the presence of mean differences between them and the SRM. Furthermore, this is exacerbated by poorer reliability than that of the SRM powermeter.

http://www.ncbi.nlm.nih.gov/m/pubmed/24896154/

sconhome

Oh I'd say the SRM was not reading properly

mloc123

I liked the SRM calibration feature. When I was training last year I was convinced mine was out of calibration (reading a little high), 20 minutes and some weights and I knew it was with 0.5% of where it should be.

mossym

AKW wrote: »

Link to these spurious claims?

My data has been fine, its the quality of headunit which has been the issue. Once the data exported to GC or TP it's easy to analyse.

i can vouch for this. akw's pm has been perfect. absolutely zero cycling has resulted in absolutely perfect readings of zero watts. 0.0% error. not sure even SRM could claim that level of accuracy.

based on current form(messing around with paddles and muddy fields) as well i envisage he could claim polar data will be accurate over the next 10 years as well....