OK, I now have the gear (iAero + PT) and I'm ready to start fine tuning my TT position. Now I need a process.
What's the best procedure for finding an optimal TT position? Should I try to adjust it on the road or should I run a series of trials and then do the analysis at the house? Which variables should I try to optimize? (Yeah, we're obviously looking for the best time; but weather and road conditions make it hard to compare times from one day to the next.)
My first thought is to try to attack CdA by using on-bike data to minimize it. Then use a series of 10 or 20 minute trials to dial it in before experimenting on a 40K.
Assuming that there's a tradeoff between position and power, does Time Advantage take that into account? Now that I think about it, I'm not exactly sure how Time Advantage works other than it figures out how long it should have taken you to get to a point and compares that to how long it actually took you to get there. But is that based on the Pin data (which may be lower if you're in a tuck)?
Procedure for finding an optimal position
Re: Procedure for finding an optimal position
First, find a nice day with steady temperatures and low wind.
Now clear out your schedule that day.
What I do is take a 2 mile section of flat road that is very sheltered from the wind. I run the live cda and time advantage both on. Then I make multiple runs on the same two mile course. I try to keep my watts very steady and so I can also compare the time over the two mile section of road (as another measurement of cda).
My last day of doing cda measurements took me about 3 hours total to get completely dialed in. This would have cost me about 2400-3000 dollars at a wind tunnel, but I did manage to save 30 seconds for a ten mile time trial.
The UCI rules concerning time trial positions has just recently changed (again) and so I am going to have to perform another day of aero testing runs to make sure I have the fastest, and a legal, position.
Now clear out your schedule that day.
What I do is take a 2 mile section of flat road that is very sheltered from the wind. I run the live cda and time advantage both on. Then I make multiple runs on the same two mile course. I try to keep my watts very steady and so I can also compare the time over the two mile section of road (as another measurement of cda).
My last day of doing cda measurements took me about 3 hours total to get completely dialed in. This would have cost me about 2400-3000 dollars at a wind tunnel, but I did manage to save 30 seconds for a ten mile time trial.
The UCI rules concerning time trial positions has just recently changed (again) and so I am going to have to perform another day of aero testing runs to make sure I have the fastest, and a legal, position.
Boyd Johnson
http://www.boydcycling.com - high performance carbon wheels and accessories
http://www.boydcycling.com - high performance carbon wheels and accessories
After field testing - how do I analyse file to show CDA chan
This may be a silly qustion but:
Then what?
I have done what seems good calibration, Then done several runs with position changes as laps within a ride file.
But how do I find out what they are telling me??
Would I have been better to do all the runs as calibration rides? And calculate a CdA for the differnt positions as separate calibration rides.
As it is, all I can see to do is compare the DFPM average for the run with the Ibike power and see what Watt saving the alternate positions give me.
Is this what anyone else has done for testing positions? How can I turn the watt saving info into a CDA for each run?
The CDA graph seems to show the varying cda, but I cant see how to extract this for a given section of the ride.
The inability to zomm into laps on the CDA graph isnt helping me much either.
I am guessing there must surely be a way to do this, but so far I cant find it??
David.
Then what?
I have done what seems good calibration, Then done several runs with position changes as laps within a ride file.
But how do I find out what they are telling me??
Would I have been better to do all the runs as calibration rides? And calculate a CdA for the differnt positions as separate calibration rides.
As it is, all I can see to do is compare the DFPM average for the run with the Ibike power and see what Watt saving the alternate positions give me.
Is this what anyone else has done for testing positions? How can I turn the watt saving info into a CDA for each run?
The CDA graph seems to show the varying cda, but I cant see how to extract this for a given section of the ride.
The inability to zomm into laps on the CDA graph isnt helping me much either.
I am guessing there must surely be a way to do this, but so far I cant find it??
David.