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From Virtual Power to Meter (venting)

I've been using virtual power on TrainerRoad for the last year and have seen some good gains in performance. My power to weight ratio went from truly pathetic to OK (2.8 W/Kg). I was hoping to break 3 W/kg by the end of the OS, but it looks like that goal will have to be delayed. My new power meter (PowerTap P1 pedals) reads between 10 and 15 Watts lower than the virtual power! 

I did the manual zero (calibration) twice, and there is no other calibration that can be done outside the factory, so I have to assume the power meter is correct. It's a little frustrating, but I suppose I should look on the bright side. The lower my power is today, the greater the upside potential in the future! Right?

Guess I should get back on the trainer!

Scott

Comments


  • Posted By Scott Imlay on 04 Dec 2015 03:59 PM

    I've been using virtual power on TrainerRoad for the last year and have seen some good gains in performance. My power to weight ratio went from truly pathetic to OK (2.8 W/Kg). I was hoping to break 3 W/kg by the end of the OS, but it looks like that goal will have to be delayed. My new power meter (PowerTap P1 pedals) reads between 10 and 15 Watts lower than the virtual power! 

    I did the manual zero (calibration) twice, and there is no other calibration that can be done outside the factory, so I have to assume the power meter is correct. It's a little frustrating, but I suppose I should look on the bright side. The lower my power is today, the greater the upside potential in the future! Right?

    Guess I should get back on the trainer!

    Scott

    Virtual power is just that...virtual. Your Powertap pedals will be much more accurate so it's largely a function of recalibrating your head and your goals around the now-real number. 

    I was fortunate enough to have an opposite experience in 2010: I had been riding with an Ergomo for years and was near the end of a 6mo cycling-only block of training, preparing for a ludicrous climbing race in California. I was going faster and faster up my usual climbs but my power was actually dropping. The Ergomo died on me, I replaced it with a Powertap and BAMM, my FTP instantly went up by ~20 watts due to having accurate readings again. So this was the once instance where I truly did buy power 

  • I bought a pair of the P1s a couple of months ago. I also have a PT wheel. I put both on my computrainer and the watts are pretty close so I feel pretty confident with my power meters accuracy.
  • Thanks Rich, Tom,

    Yes, I trust the P1's. Trainer Road warns you that virtual power may be off by a significant amount. No worries. It doesn't really change anything about my training - I just adjust my FTP and move on.

    Tom, I am correct about the calibration, aren't I?

    Thanks! 

  • As my ability to generate power on the pedals deteriorates little by little every year, I'm learning to value other tools available, to mazimize the one thing we actually want to be doing: going as fast as possible for as long as possible. Those include body position (sometimes called bike fit) and riding at a steady power output. Both can be improved no matter one's w/kg.
  • Al, I'm about a decade behind you in age but light years behind you in experience. I suspect I'll be able to improve my power to weight ratio for a few years yet, but it is pretty low at this point. Given my low W/kg, I suspect my VI is pretty bad on the typical Pacific NW bike course.

    I have an 11-speed Shimano 105 with a 50-34 crankset and an 11-28 cassette. Would you recommend I switch to an 11-32 cassette for Coeur d'Alene?

  • The current version of the CdA course is all on highway grades - nothing at all like we can see here in the back roads of the Puget Sound area. At most, 5-6% steep. A compact crank with 11-28 should do just fine. It's what I used in 2014 when I last did the race. Checking my race file, I see that I went up the main climb of about 450'/1.85 miles in 14:30 minutes @ avg cadence of 82, power of 2.25 w/kg, IF of 0.7, VI of 1.0, in the aerobars the whole way. Into a 15-18 mph head wind 

    I'd say if you find that trying to go 0.7 IF on a 5% grade means you have to grind in the 60s-70s, rather than spin in the 80s, then yes, you'd benefit on the CDA course from going up to 32 teeth in the rear. That would for sure help you in the shorter steep pitches (8-12+%) we can see over here.

  • I hear you.. my VP with TR was 339!!! and now with a real pm (power2max) its now at 238. Anyhow, VP was for training purposes and was using same wrong numbers hah..
  • I had a (very old) powertap hub that gave me impressive numbers. The combination of a forced lay-off from the bike & new P1 pedals was very nearly soul-destroying when I got back on it. That said, the numbers have crept up as I've got back into shape. I'm amazed by the quality of the algorithms that Trainer Road uses!
  • X2 on Tom Glynn's comment. I was freaked out by the difference in power read on TR reading off my powerbeam trainer and what my new P1 pedals were saying (I thought they were wrong) slapped on a powertap hub and got almost identical readings from the hub & the P1s.. Totally trust them (and not liking my powerbeam!)
  • Scott - do you TrainerRoad with the Powerbeam? If so, set it to use the P1s to control the ERG resistance on the trainer instead of using the internal power output from the trainer. It is the best of both worlds, and you will get a more realistic workout, as you would on the road.
  • I've never used the virtual power, but, I can say that I have a quarq, powerbeam pro trainer with built in pm, and a wahoo kickr with a built in pm, and the power readings are all different. They going from showing me with the most power on the kickr, followed by the quarq, and the least on my powerbeam. All that being said, whether you are using any of those or virtual power, it is just a number, and a tool to track your progress, especially on the trainer.
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