Switching from Polar to Powertap

I'm glad I made the switch to the powertap even if I'm not as powerful as I thought I was. At least I now know the truth.

I do have one problem though.I need to revise my ftp back down. This creates issues. All the data collected with the Polar is now irrelevant as it is an overestimate. All my charts are dominated by these inflated numbers and this makes it difficult to see gradual improvements in my numbers.

Is there a way to normalize the numbers that were obtained using the Polar to somehow match the numbers the powertap produces?

maybe I can modify the numbers using some formula in excel? Any ideas.

You could, but what a pain in the **** and for better or worse the numbers on file are what you actually recorded.

How about ending your "polar season" by setting a new season end date and then creating a new season start and end date that reflects the remainder of this year with your PT and keying your charts "this season". You don't have to do this with all charts if you want to keep a loose eye on training hours or duration or kj work from the beginning of your actual training year and you can even keep your PMC keyed to whatever date you want. But it allows you to only see recent peak values for charts where that's important to you and over time the Polar data will become less and less relevant.

-Dave

Thanks Dave that makes sense. Ill do that. Ill start a new season. Eventually the Polar data will be like you said "irrelevant". Ill still be able to use the PMC using the dates which included the Polar data.

cheers.

Hi, I just stumbled across this thread. I'm also a polar user considering to change to a powertap. Reading the above, my first question is, is the polar powerdisplay really so far off? My impression is that, in low cad. the intuitive pressure on the pedal feels more intensive and shows lesser watts than in higher cad where it feels easier. This is a bit disturbing to me. I' m absolutly convinced of training with a pm but not if the data is not reliable.
Peter

It really isn't that disturbing when you understand Power = Force x Velocity.
All things being equal and relative, if the percent change in force is less than the percent change in velocity in a low cadence vs. high cadence test, you will put out more power at the higher cadence and it will feel easier because you'll be recruiting less fast twitch(feels more intensive) muscle fiber and using mostly slow twitch(I could ride all day) muscle fiber.

My question is why was your Polar unit wrong? Was it set up incorrectly? Bad unit? Wrong chain weight?

My Polar CS600 reads virtually identically when doing 20-min tests as compared to my powertap-equipped PT300.

Just curious.

__________________

'07 S-Works Tarmac SL, Polar CS600+Power
2008 Cervelo P3C, Zipp 900c+808

'07 Specialized Epic Marathon w/Crossmax SLRs
CycleOps Pro 300PT Indoor Cycle Trainer (my winter ride)

i had 2 Polar units for several years prior to switching to Powertap & Ergomo, then 2 Powertaps. i have never done side-by-sides (a Polar & Powertap on the bike at the same time), but my recollection of the Polar power values I used to get on the rides I repeat frequently were not that different than either my Powertap or Ergomo units. Again, recollection is not the same as empirical evidence, but I recall telling myself on the first few Powertap rides, "that damn Polar unit was pretty accurate after all."

are you sure you had the chain weight, lenght, and S value set correctly? was the pickup device installed properly on your chainstay?

I am very sure that I set it up exactly as described. I weighed the chain, I placed the sensor close to the chain.

Whether or not it was set up correctly is irrelevant. I am confident that the powertap is set up correctly and giving me accurate results. The difference between the PT and the polar is around 10-15 %. So you can see why I was frustrated with the data I have collected and built all my graphs around for the past year.

I spent hours setting up the polar having read post after post of other peoples experiences so I knew every trick and technique for getting it right.
I persisted with the product, I had issues with the battery pack contacts. The darn thing wouldn't record sprint data accurately. I knew I could push our more than 800 watts in a sprint. I could not stand that stupid 1 hour 53 minute storage limit at 1 second sampling rate.

I am so happy I made the switch. The only thing I miss about the polar is the altimeter.