AeroPod, PowerPod and Newton

Hi John

I have received the PowerPod and have taken it out for about 8 rides and really enjoying it.

Question on those who ***interchange wheelsets on the one bike***.

I have two sets of wheels as follows:
– A pair of climbing wheels (Mavic R-RYS with 25mm clinchers); and
– A pair of aero wheels (Bora 1 50mm tubular with 22mm front/25mm rear).
(Both wheels weigh almost the same)

Obviously the aero wheels are much more aero… so how do we “tune” the profiles in ISAAC to cater for this effect on the PowerPod readings?

I remember reading somewhere that you can update the CdA setttings (which I know nothing about btw).

Would you be able to give me some advice so I can get more “accurate” readings between the two sets of wheels.

This is something I'd also like to know about as I'm in the same position. My aero rims are 50mm Spin tech wheels

Hi John

When you get the chance can you reply to this. I posted it on DCR, and you asked me to post it here which I've now done.

Appreciated.

This topic wades into the really fine points of wheel design...

Certainly, many wheel manufacturers claim that aero rims have less drag, and certainly they LOOK like they should have less drag...

But what is the reality? To get some answers I called my good friend Boyd Johnson of Boyd Cycling, http://www.boydcycling.com

Boyd builds amazing wheels, and here is what I understood from my conversation with Boyd (if anything I say here is wrong it's my fault, not his...):

1) aero wheels show their primary benefit in cross winds; in "straight-on" winds they have some gain, but only at very high speeds (30 mph)

2) He estimates that aero wheels reduce drag by about 0.001 CdA in 15 degree cross winds

3) This translates into watts savings of 2-7W, depending on bike speed and wind angle

4) Though the watts savings are real, the magnitude of the wattage gain is within the measurement accuracy of power meters. For example, at 20 mph, on the flats a cyclist will require approximately 200W. Aero wheels might save about 2W...worth it if you're trying to win the race, but not measurable with any power meter.

5) at 30 mph, you'll get about 10W of advantage, but you'll also require to hold about 350W to ride that fast...again, the aero wheel benefit is real, but not measurable by a PM.

Here is a page that shows the relationship of yaw angle and grams of drag:

http://www.boydcycling.com/aerodynamics

So, honestly, if you're racing most definitely use your aero wheels...they will help. But I would not adjust your PowerPod profile, as the benefit won't be noticeable within the +/- 2% measurement window of any power meter.

Hello, I'm a new user of powerpod, and this is my first powermeter.
I use this topic because also me use two different type of wheelset (1 pair with carbon rim and the other in alloy rim),
but the difference is not of aerodynamics, but weight.

The bicycle with training wheelset and accessories it weighs 1 kg more than the carbon wheels.
I have calculated the difference in term of power with an excel file in 6% uphill, that I use for testing me, and the differences adding only 1Kg are only 3 Watts.
In this case is useful change the profile adding the extra weight?

Thank you
Fabio