Hmmm. Given what you've said above, PowerCal might've been even better.

So, how would you know how to use power as a pacing metric if you don't use it to train?

I do use it to train. It's just not primary. Based on training, I know that I can ride/ race at 210 watts with heart rate between 127-137 for 112 miles

powertap cons:
state of drivetrain affects power reading

?

It accurately tells you how much power you are applying to the rear wheel. Definitely better for field testing and I can't think of a reason why it would be undesirable for any circumstance.

I use a a Powertap on one bike, a SRM on a second bike and Look Keo Power on a third bike (+ a Powertap disc on my MTB) so definitely not saying the Powertap G3 is not a good option, I really like it.

But to answer your question, yes there are scenarios where this particular aspect of the Powertap is undesirable :
- let's say you do FTP test with your Powertap on a clean and in good shape drivetrain (without a bad crossed chainling like doing the test on 52x25 in a climb...), you get a number that is close to what you are really pushing on the pedals.
- you ride 2000 miles during the next two months in all weather and don't really clean your bike and your chain did wear out in the mean time... you go out to do a second FTP test with that drivetrain in that state... it shows 5 watts less on your FTP compare to what you did 2 months ago. Does it mean the two months of training did not provide improvement ? Maybe... maybe not. It is quite likely you pushed 5 more watts on the pedals VS last time but what the rear wheel received as torque to transfer was 5 watts less ! Meaning your bad drivetrain made you loose 10 watts on the road even though you did improve physiologically.

10 watts at 300w is like 3% which can be the difference between a perfect drivetrain and a bad drivetrain... so yes state of drivetrain can lead to unexact information with a Powertap. With some care and good will this is kind of a non issue though ;-) .

A lot of us use 3M electrical tape to install the AeroJacket wheel covers. Not sure if wheelbuilders does that method, but you may want to look into whether they do that or not. Otherwise, consider ordering the disc cover separately (specifying without the bolt holes) and installing it yourself. I forgot to specify without the bolt holes and simply ended up covering the holes with electrical tape on the inside of the cover.

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Madison photographer Timothy Hughes | Instagram

Do you want HR to rise throughout the competition or power to fall? One of them will happen.

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Endurance coach | Physiotherapist (primary care) | Bikefitter | Swede

Thanks for the insight. In my case I think I will be OK. I will be using it mostly on my tri bike which will not see nasty conditions as much as a MTB.

Additionally I am super anal about cleaning, lubrication, tuning and replacing worn chains. I use the park chain gauge and change them out once they stretch .75 inch

I disagree. The Powertap at least does a better job of relating power and speed since the drivetrain variable is removed. Honestly there shouldn't be a lot of variation there due to wear and crosschaining. If there is, then you can do something about it.

Powertap scenario: You feel like you are getting in better shape but your power numbers aren't going up.... because your drivetrain is effed up.

Crank PM scenario: You feel like you are getting in better shape and your power numbers are increasing, but you aren't going any faster... because your drivetrain is effed up.

If you are focused on your power #s, then a crank PM can make it seem like everything is fine when it isn't. Which is more important...speed or power? Speed, right? Isn't that why you got the PM in the first place?

^^^Ummm...yeah...don't do that.

If you're detailed enough that you're using a power meter in your training because it's a better way of quantifying load, why would you let your bike maintenance go all to heck? I don't get that...

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http://bikeblather.blogspot.com/

And with these magical inventions called master-links, owning a "race" chain that you keep very clean seems a wildly sensible solution for anyone who does dedicated testing days (i.e. use said chain for testing days and racing only and make it a "training" chain after 2000 miles of use or so).

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The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important.

-Albert J. Nock

rruff,

I understand what you say. And again I like my Powertap as much as I like my SRM so I'm not complaining about the way the Powertap measures the power, but we are talking pros & cons here ;-) .

You ask why I bought a powermeter in the first place, the answer is I bought a powermeter in the first place to measure the level of my effort. Sorry to disagree but speed is secondary for me (unless you are trying to do aero testing at a given speed with your powermeter but that's a different story...). Having an optimized drivetrain is obvious for me for racing but I can give you another example since my last one was probably a bit extreme :
- my race bike has Berner rear derailleur, Atomic coated chainrings pulleys and cassette, quality ceramic bearings in pulleys and BB and very well prepared chain (not the point going into details here) : for a given effort I will read X power with my SRM and Y power with my powertap.
- my training bike even with a clean and in good shape drivetrain "only" has a standard drivetrain, 11t pulleys, standard BB, standard oiled chain : for the SAME GIVEN EFFORT I will see X watts if I install my SRM on that bike but I will see Y minus a few watts if I install the powertap on that bike. I don't care what the speed is, I'm not training to get speed numbers, I'm training to learn to sustain some effort (effort being 30mn sprint effort of 4h40mn Ironman effort...).

I'm not saying this is a big deal, I'm just saying the difference does exist, if you improve your drivetrain with a Powertap, your power numbers will increase even though your body did not. We are talking road environment here, but some people like me also use powermeters for MTB or cyclocross and in those disciplines you can see bigger difference between crankset based powermeters and rear hub based powermeters. If it's proof enough that I feel it's not that bad, I chose Powertap for MTB, not SRM or Stages.
So there is nothing wrong with Powertap, the point I'm trying to make is that this "con" of Powertap does exist, not a deal breaker at all for me and mostly a non issue for road use as long as we don't get stupid by doing one effort with a clean drivetrain and trying to replicate and compare the effort later with a shitty drivetrain, but I still see this as a "con", if you see this as a "pro" then this is one more reason for you to choose a Powertap and I have nothing against that. It won't be the first time a feature can be a good thing for one person and a bad thing for another person, I'm all for diversity of oppinions and needs :-) !

;-))) Of course I don't do that.
It was just an example to explain you have to pay slightly more attention with a Powertap, like I answered to rruff mostly a non issue for road, possibly a bigger issue for cyclocross and MTB but nothing I'm really concerned about though.