Aero testing - using the time advantage feature

[Steve_Davidson]

A friend of mine has recently taken the plunge and upgraded his SRM to the new wireless model and purchased an iAero with RWS. We compete against each other at club and open TT events and I've been creeping closer to him since I started tweaking my position with the iAero in the last few months of the season.

So now we both have wireless SRM's and iAero's and we are planning some serious aero testing when we get good weather windows over the next few months and beyond.

My question is:- what is the best way to use the time advantage feature? I had figured that it might be best to do a baseline calibration and then do a series of 2-mile runs at similar speed and do a trip reset between them so that I can make sure the calibration settings are good for each run. This is so that the time advantage is reset to 0. Or is it possible to reset the time advantage using laps? I haven't used the feature yet.

My aero testing so far has been a series of calibration runs (4-mile rides) and then a review of the ride data later. I found this method OK for checking a few positions but using the lap feature could be quicker as I could do shorter runs and get more testing done within a tight window.

I'm interested in other peoples thoughts and experiments (successful or not).

cheers

Steve

[coachboyd]

It sounds like you are using the same method I use for my aero testing.

I do my out and back calibration ride on the road that I am going to be aero testing on. This way road conditions stay the same and any small changes you see will be from position, not from a change in crr.

I create the baseline profile and send it to the iBike (gotta love those new netbooks that are super portable as my aero testing road is about 20 miles from my house).
Once I have my baseline profile I will do my runs on that same road with the time advantage screen on. Using the time advantage will give you instant feedback as to if the new position is faster or slower.

Something I have been trying as of lately is to do my aero testing on a 1/4 mile running track. They are at most high schools around here and most of them are paved nowadays. You have to do this on a very calm day in terms of wind. I then ride exactly 10 laps around the track (starting at speed) at a set wattage. The user intervals are great for this as you can hit your target watts everytime. So, say I ride 10 laps at exactly 250 watts, then I stop the timer. Let's say my time was 6:30. I make my position changes and then ride another 10 laps at exactly 250 watts. If my time on this one was 6:25, the position is better. If you want a more advanced way to look at this, you can take your power file and use the Chung method to determine your actual cda (google Chung method, it's slightly complicated).

[Steve_Davidson]

Thanks Boyd.

Yeah, I've used virtually every method there is for aero testing and the VE method with wind data has given me my best results. What I'm trying to do is to make it as simple as possible for someone who doesn't want to spend time analysing the results on the PC.

We've got a concrete cycling track about 24 miles away but it has a horrendous bumpy surface and very inconsistent. The local council won't let us near the running tracks so we've got a few stretches of road to use but the problem is lining up our free time and the weather to get a good session. My best sessions have been on late summer evenings when the wind has dropped and there is no traffic around but winter is altogether more difficult to get good conditions. Suppose it's all part of the challenge and fun of trying to improve things.


cheers


Steve

[ludlaw]

I have done the reset and time advantage method but I am hoping I could get a cda number for each position change. Is there any reason that you can't do a series of calibration rides, one for each position change?

[coachboyd]

No reason at all. If you ride out and back on the same stretch of road, you can do a calibration for each and compare.

When doing this you may want to incorporate a small hill into your out and back. This way you can compare the numbers at slower and faster speeds, and this helps to pry apart the crr and cda numbers. Two miles out and two miles back should be plenty, but if you can do a little more it wouldn't hurt (if you can find the road).