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Reconciling a new and an old Powertap

Dave TalloDave Tallo
in General Training Discussions

Here's my challenge:  I've trained and raced with one powertap wheel for the last 5 or 6 years.   But I'm using a different wheel with a different powertap in Kona. 

I've already put about three weeks of riding on the new PM, and I am seeing some higher-than-normal numbers.  However, i'm not aware of any way to accurately compare the two. 

The bigger challenge is there's a lot of noise during the changover.  Maybe I'm actually stronger at the end of the season and putting out  bigger numbers.  Or maybe the ten or fifteen degree temperature drop is giving me newer legs. 

Any advice?  Note that i don't think a 2x20 test is in the stars this week. 

 

 

 

 

Comments

  • rboglerbogle

    Just spitballing here. So, if you dont have time for a proper test on the new wheel (too close to K day, for that hard an effort) , maybe do a informal quickie comparison: say ride a 3-5 mile stretch of road, repeat with each wheel holding the same Percieved Effort and Avg MPH and compare watts. Start with your oldie and ride say @ IM watts, then put on the newie and hold the same MPH and PE. Should give you a ball park offset of watts, if any, between the two, so that you know what watts on the new wheel equal from the old wheel.

     If you are worried about a non-constant difference (non-linearity) at different outputs, you could repeat the test for each zone on a short effort, and then you should have generated a rough calibration curve, but that might just take more time than its worth. I'd say as long as you know what your IM watts should be on the new wheel with respect to the old one you are good to go.

    I'd say no two pm are ever going to be the same, too many tolerance variabilities. So everything you do is a relative to the the pm you have and not a precise absolute #. So this is just a quickie calibration, trying to hold as many variable as still as possible. 

  • Steve WestSteve West
    Dave - how about a pair of 10' FTP intervals on a trainer. Keep mph, cadence, psi, & gearing same for both setups. Should be able to see any glaring differences without too much problem.
  • Peter GreaggPeter Greagg
    Dave
    What about the stomp test?
    http://thecyclingaddiction.blogspot.com.au/2012/10/2012-10-6-powertap-sl-static-torque-test.html
  • tim cronktim cronk
    I would stick with the data you have accumulated with the new PM over the last 3 weeks. That should give you 3 good long rides + the 1 more you will probably do in KONA = 4 rides of good data..... IMO raceday is no longer relevant to FTP so I wouldnt compare any new FTP data with old , its all about sustainable power , or more correctly that which you can sustain for 5hrs or more ....

    What were your last 3 rides like?
    Similar RPP ?
    What was the NP on each ride? Similar or big discrepancies?
    What do you normally ride for an IM target? A percentage of your last know FTP test or the NP of a RR ?
  • Dave TalloDave Tallo
    Thanks, guys. I'll probably do a hybrid of trainer and stomp tests ... but unfortunately, one wheel is a clincher and the other tubular with a uber-fast tire, so I'm suspecting there will still be some noise in the differences that arise from rr.

    Also, to Tim's point, I have one more RR that I'll do on the Kona course on Sunday, so this should probably settle things once and for all.
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