Using CdA / Testing Protocol Advice?

[b9rel8tor]

I will be using the CdA function in my ibike in the coming weeks to see if I can eek out any speed gains in time for Nationals, June, 14.

Some questions that I hope the group can help me with:

- - Is the CdA function precise enough that I will be able to tell the difference between, let's say, helmet positions?

- - My iBike is mounted between my aero bars (see photos below and attached). I seems as though nothing will interfere with it (one photo shows my hand on the bar, just in case). Is that right?

- - I have an Xlab "torpedo" water bottle that mounts above and behind the iBike - again, it seems like it shouldn't interfere, but I wanted to check (it mounts on the carbon platform that is velcro'd to the TT bars in the overhead shot. I can see the iBike when the bottle is in place, so the whole body of the iBike is in front of the bottle).

- - The ONLY place where a mount fits is on my aero bars. This isn't a problem except if I want to try a different angle for the bars. The iBike tilt will be incorrect, and probably the wind sensor will be affected also? What protocol should I use if I want to try a different TT bar angle? Do I need to do a cal ride in-between CdA tests? What's the best way?

Thanks all for your help!

Peter in StL

[Velocomp]

Attaching Newton to your TT bars won't work. The bars are too flexible for the required accuracy of CdA measurement.

Find a way to attach Newton to your top tube, then run a hose from Newton to the front of your bike. This will work great.

[b9rel8tor]

Hmmm . . . has anyone done this (attach an iBike to the top tube)?

I have a Cervelo P3, which has two water bottle-style screws in the top tube for mounting a bento box (which I have done - a fabric pouch for spare tube etc . . . I take it off when I race). Maybe I can use one of the screws?

This means that I won't be able to view the iBike while riding in aero position . . . but I guess I can check the results afterwards?