General Discussion Triathlon Talk » 2015 P2 w/ FSA Gossamer Crankset - PM Options? Rss Feed  
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2016-06-02 2:44 PM

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Subject: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Just wondering if there's anything available that doesn't break the bank. I have no idea what's out there, and what I've read.....I don't know if they'll fit my bike.

Hub-type is not an option (for me).

Names are fine. I'll do my own research. Hoping someone was in my shoes a while ago and can point me in the right direction.

Thanks.


2016-06-02 4:58 PM
in reply to: nc452010

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Elite
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?

Power2max likely has one for you.  Send them a note from their website with what you have and they will tell you your options.  They've been very responsive anytime I've dealt with them.

2016-06-02 4:58 PM
in reply to: #5185043

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
I bought a close out Stages SRAM PM last year and when I picked up my P2 earlier this year they simply swapped cranksets, though it does require an adapter. If you're interested I think Stages has some close out deals going on.
2016-06-02 5:12 PM
in reply to: axteraa

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Master
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Yep--I have pretty much the same setup, but a slightly older P2 (2010 or 2011--forget) and have a P2Max. You specify the crank length when you order. The PM is on the crank and it pretty much just replaces your existing crank. As I recall the installation was very simple and nothing had to be changed on the bike, just replacing the crank.
2016-06-02 6:27 PM
in reply to: nc452010

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Pro
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
My wife has a P3 and uses a SRAM Red Quarq. Works perfect!
2016-06-02 8:51 PM
in reply to: #5185062


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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
https://store.stagescycling.com/mobile/stages-power-meter--energy-38... $349 close out.

I have same bike. Just ordered this PM. left side only which is fine with me. Price is hard to beat. Some people report issues with dropouts for ant+ when bike computer is on BTA. I'm planning on using it with polar m450 over Bluetooth smart so not really concerned.


2016-06-03 6:42 AM
in reply to: TriTampa2

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
I see a lot of people knock the Stages power meter for dropouts so I thought I'd post my experience and setup in case it helps anyone else. I have an Xlab Torpedo Versa installed BTA with a Garmin 500 just above and slightly in front of the water bottle and have yet to have a dropout. I haven't been so lucky with the 920 on my wrist.
2016-06-03 7:39 AM
in reply to: Toefuzz

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Originally posted by Toefuzz

I see a lot of people knock the Stages power meter for dropouts so I thought I'd post my experience and setup in case it helps anyone else. I have an Xlab Torpedo Versa installed BTA with a Garmin 500 just above and slightly in front of the water bottle and have yet to have a dropout. I haven't been so lucky with the 920 on my wrist.


I have almost the exact same equipment (I use the same BTA XLab and a Garmin 510). I only use the 920 in tris......for elapsed time and to check run pacing.

I appreciate ALL of your replies. Great information.
2016-06-03 9:06 AM
in reply to: Toefuzz


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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Originally posted by Toefuzz

I see a lot of people knock the Stages power meter for dropouts so I thought I'd post my experience and setup in case it helps anyone else. I have an Xlab Torpedo Versa installed BTA with a Garmin 500 just above and slightly in front of the water bottle and have yet to have a dropout. I haven't been so lucky with the 920 on my wrist.


good to hear. I have the profile design fc BTA. I do need a new bike computer though since I just want to keep 920 on my wrist the entire time. the polar m450 is a good price point since it's $140 and has bluetooth capability
2016-06-03 5:34 PM
in reply to: TriTampa2

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Master
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
At the time I bought the P2Max (I think it was a Black Friday sale) they had a bundle deal with the Garmin 520 (bike computer). I've been very happy with it. No issues with syncing with the PM. Pretty much my only issue is that sometimes it will drop the HR signal if I lean back to get a water bottle out of the rear mount, or stretch too far away from the computer. But this may be a transmitter battery issue--not sure.
2016-06-03 6:20 PM
in reply to: 0

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
A P2max is a very accurate and precise PM. Accurate and precise have different meaning

A stages is less accurate and less precise for some riders. This may be acceptable for some There are applications where it's "good enough" other applications where's it's unnacceptable, for example aero testing.

But it's probably not fair to say they are equivalent, hence the price difference. There is a class of PMs, one step above (Quarq, P2Max and others)

But at $3xx the stages may be good enough for some. But knowing it's limitations is important.
The left/right thing makes it potentially +/-8% for me. The weakness around it's connectivity is a concern.

But at sub $400 some may be willing to live with this and that makes sense for them,


Edited by marcag 2016-06-03 6:44 PM


2016-06-03 6:53 PM
in reply to: marcag

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?

Originally posted by marcag A P2max is a very accurate and precise PM. Accurate and precise have different meaning A stages is less accurate and less precise for some riders. This may be acceptable for some There are applications where it's "good enough" other applications where's it's unnacceptable, for example aero testing. But it's probably not fair to say they are equivalent, hence the price difference. But at $3xx the stages may be good enough for some. But knowing it's limitations is important. The left/right thing makes it potentially +/-8% for me. The weakness around it's connectivity is a concern. But at sub $400 some may be willing to live with this and that makes sense for them,

Agree.  The problem with one sided power and knowing if it's "good enough" is that you need to do a lot of sampling with a PM that can read L/R individually before you can determine it.  Marc mentioned that he can see a +/- 8% which would be worse than a HRM and most likely worse than most people's general sense of RPE in terms of pacing.  So it's possible a one sided PM can actually frustrate you with conflicting data and/or cause you to pace yourself worse than if you didn't have one at all.

So at a certain point you have to wonder if a more affordable power meter that only measures one side is even worth paying any money for.  I'd certainly consider a one sided power meter for maybe my CX or commuter bike...but I wouldn't pay $5 for a one sided power meter to use on my primary road bike for training and racing.  The differences, or possible differences would drive me crazy since I would never know if my L/R balance is consistent or not...hence is my data consistent or not?

 

2016-06-05 4:29 AM
in reply to: Jason N

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Great info guys.

Let me tell you why I want one......and you can tell me if the difference would matter to ME, or not. I honestly wouldn't be looking, except I'm now thinking of signing up for a full in 2017. I want it for pacing. Period. If I'm going to get one, I'd also like to use it in my HIM in Sept.....but, I could also be talked into just collecting data from here on out (this year) and using that data for next year (and to train by, this winter).

On the other hand, I also might do another 70.3 race in August. Now that race has a very challenging bike course. I'd love to think I could buy a PM next week and have information I could use by August to get me through that course (very hilly).

I'll defer to you guys AND thank you for your very good information.
2016-06-05 9:30 AM
in reply to: Jason N


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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Isn't the most important thing that the power meter readings are consistent? I understand with a left only reading the reading will not show the imbalances you may have in power but does that really matter that much? If I train and race with the same power meter and base my race plan power number on that training what difference does it matter if it's one side or dual sides power meter? If so, how? If I have a power imbalance between right and left I don't imagine that imbalance would vary wildly .
2016-06-05 9:33 AM
in reply to: 0

Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
I spent days and days reading DC Rainmaker reviews on PM's. I pulled the trigger last year on a P2M and have not had any second thoughts. As I am toying with a new road bike this year, a P2M meter will be installed on it upon purchase.
Joe

Edited by Puppetmaster 2016-06-05 9:33 AM
2016-06-05 9:35 AM
in reply to: Hot Runner

Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Originally posted by Hot Runner

At the time I bought the P2Max (I think it was a Black Friday sale) they had a bundle deal with the Garmin 520 (bike computer). I've been very happy with it. No issues with syncing with the PM. Pretty much my only issue is that sometimes it will drop the HR signal if I lean back to get a water bottle out of the rear mount, or stretch too far away from the computer. But this may be a transmitter battery issue--not sure.


How do you like the screen on the 520? I am getting older and the 910xt on my wrist is getting hard to read. That 520 seems to be a really nice unit, but no place aroudn here has one to see.
Joe


2016-06-05 10:13 AM
in reply to: #5185043

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Elite
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
My left/right balance varies with cadence. At lower cadence my left leg dominates while it's my right at higher cadence. I have workout files where a stages would under or over report power by as much as 20w. That's a sure fire way to mess up an ironman. That may or may not be the case for you but with a stages you just don't know.
2016-06-05 10:38 AM
in reply to: 0

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Originally posted by TriTampa2

Isn't the most important thing that the power meter readings are consistent? I understand with a left only reading the reading will not show the imbalances you may have in power but does that really matter that much? If I train and race with the same power meter and base my race plan power number on that training what difference does it matter if it's one side or dual sides power meter? If so, how? If I have a power imbalance between right and left I don't imagine that imbalance would vary wildly .


Power imbalances are not necessarily consistent across cadence, power levels, fatigue

This is what makes a stages potentially imprecise and innacurate
The doubling of the left leg (if there is an imbalance) is what compromises accuracy
The fact our imbalance may vary over a ride is what compromises precision

Arend gave an example where for him it varies with Cadence. For me, it varies with power. If I ride at 70% of threshold I can be 53/47 which means a stages would show me 6% over reality. I am more 50/50 at 100%. I also notice I become more imbalanced over time. I can be 55/45 at the end of a long ride.





Edited by marcag 2016-06-05 10:40 AM




(precision_accuracy.png)



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2016-06-05 12:07 PM
in reply to: marcag

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Elite
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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?

Here's a specific example from one of my workouts.  In the graph, the blue line is cadence, yellow is power, the red is L/R balance (above the line is left, below is right).  In this interval, about 3/4 of the way through, I shifted gears, my cadence dropped and you can see the balance shifted to my right leg.  For the two parts of that interval average power was 331w for each of them - first part L/R balance was 51.4 / 48.6%, second part was 48.9 / 51.1%.  Doing the math to see how a left only PM would report that gives this

331 * 51.4% * 2 = 340
331 * 48.9% * 2 = 323

Conclusion from a left only PM would be that it's harder to produce power at a lower cadence....





(LR-cadence.jpg)



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LR-cadence.jpg (51KB - 8 downloads)
2016-06-05 1:35 PM
in reply to: axteraa

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Well, let me ask another question......

Would a computrainer session (or, series of them) show me whether or not I had a L/R imbalance? And, if I didn't, would I be OK to go with the cheaper version?

Thanks.
2016-06-05 4:04 PM
in reply to: marcag


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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?
Makes sense. For me, at least right now, at $349 it's in the good enough category. Is it perfect, no. But it will help me train and race better. If money were not object then that would be a different story. I'll certainly settle for a left only power meter over no power meter.


2016-06-06 12:17 PM
in reply to: nc452010

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?

Originally posted by nc452010 Well, let me ask another question...... Would a computrainer session (or, series of them) show me whether or not I had a L/R imbalance? And, if I didn't, would I be OK to go with the cheaper version? Thanks.

Probably not.  Imbalances can change not only within a ride, across different cadences, different effort levels, but also levels of fatigue.  Your imbalance may vary the day after a long run, or when you are fresh and tapered.  It may vary during the beginning of the season compared to the end.  It may vary when you do a bike focus compared to not.  The possible differences are endless and often times totally unpredictable and there is no way for you to know for sure.  If you do enough googling, there have been quite a number of studies on pedaling balance variability.  These studies were done before the advent of one sided power meters, so they are not biased or funded by a company trying to discredit their usefulness. 

2016-06-06 2:00 PM
in reply to: Jason N

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Subject: RE: 2015 P2 w/ FSA Gossamer Crankset - PM Options?

Below is a pretty good blog post that touches on variability of L/R power balance.  He also has links to some of the studies done on pedaling balance.

http://alex-cycle.blogspot.com/2013/11/left-right-out-of-balance.html

So let me start by stating something already very well established in scientific study of pedaling.

Asymmetry in power production is normal and everyone will have a different L-R power balance. It's also well established that asymmetry is also variable and will vary with:

  • power output, absolute and/or relative
  • cadence (or torque)
  • fatigue
  • and likely a few other factors such as bicycle position, seated v standing and so on

Here are just a handful of links (updated October 2014) to study abstracts to emphasise this point about asymmetry being both normal and variable:

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