Question for Power Geeks from Wannabe Power Geek
Here is my dilemma. I just bought a Quarq Cinqo (thanks, Rich) and am in rapture with it. The unit works great, it loads of fun and I can use any wheel I want. The Cinqo is on my road bike.
On the Time Trial bikes I am running my Powertap G3 laced into a Zipp 404s. Two power meters was not the original plan, but thing just evolved that way and since I am constantly changes bikes depending on the ride it really works out great. But, I has created an interesting situation. The numbers don't seem to jive with each other. Which is no big deal, but as start planning my race pacing for Wildflower it has got me thinking....
I am really new to racing with power and sort of racing in general. Wildflower is my first 70.3. To date I have been doing sprints and basically just racing at my threshold, but I degress. The thing is I can make more power on the road bike, as reported by the Cinqo then I seem to be able to on the TT bike as reported by the Powertap. The RPE seems the same but the watts just seem lower by 10-15%. I can spike the watts on the TT to hit the road bike numbers with no trouble, but over a given period of time the watts are lower.
This is not a big deal because I am not hyper focused on the number for sake of the number. I just use it as a measuring stick for training and pacing. So the question is - is this normal road versus TT or is this Cinqo versus Powertap? Because, now I think I need to test on each system and have two FTPs depending on the platform for training and racing.. Or I could just swag it..
Curious to hear your thoughts... As I said, this is sort of geeky.....
Comments
Dino - as a general rule, we're able to generate more power on a road bike than a TT bike. I think it's due to being able to generate more power in the upright position than laid out in the aerobars. BUT...thanks to the aero advantage, less power will usually generate more speed, and besides leave your legs fresher for the run. So don't try to compare the two. IOW, for example, it might take 3.0 w/kg to go 20 miles in an hour on the road bike, and only 2.8 to go the same speed on the TT set-up (assuming your are positioned correctly)
There will also be differences between the Quarq and the PT - heck, there probably are differences in individual units within the same brand. Meaning the exact same effort level might generate different power numbers between the Q and the PT. You can of course demonstrate this by putting those Q cranks on the TT bike, or the PT wheel on the road bike (assuming you have two different head units to record each separately.) So what you need to do is make sure you (a) are training on your TT bike enough and (b) know and use your TT bike power numbers for plotting race day strategy. And for sure don't get into a competition with yourself and get all worked up over the different numbers you generate in the two different scenarios. It's like worrying about indoor vs outdoor watts, or comparing run to bike heart rates, or swim speed with or without a wet suit.
Dino,
What Al said. For you specifically, you definitely want to nail down your FTP on the tri bike. The best local TT route is to do 2 x 20 on the Santa Fe Dam, in the aerobars.
Absolutely agree w/ Al. It is now spring so time to focus on tri bike and get a FTP test on tri bike then use those numbers for your training. Of course you also want to make sure both units are calibrated too..
In the end, it is the power measurement you use while racing that matters, so Al's advice is the way to go, get your FTP on the tri-bike.
As far as I know, no head unit (Garmin, Joule, etc) will accept signals / record data from two powermeters at the same time. You would need to have two head units on the bike at the same time for this to work.
Short answer is just ride the bike/PM that you're going to be racing exclusively, wrapping your head around those numbers.
I just read a forum thread somewhere...either on Slowtwith or Competitive Cyclist(?) where someone did this...Quarq was consistently4-6 watts higher...which...there deduction was...made sense because there is no loss of power through the drive train when measured at the crank...in the end ...it was a wash...as long as consistency remains it didn't matter.
Dude, that would be awesome. I'd be really curious to see a power vs. speed profile on a trainer for both meters used at the same time. I suspect that one curve would be roughly a constant multiple of the other (say, around ~0.95), within suitable error bars. It would be a really great check for the consistancy and reliability of the power meters.
The scientist in me will start using words like "calibration" and "small error in large number", but the bottom line is to get yourself calibrated into the FTP that comes up in your race-day bike setup and used it. All the bits about 5 watts here and there for different meters don't matter AS LONG AS your percentages are based off the same system you measured on and the meter isn't ridiculously wrong.