iSport - Calibration Numbers

[voodoorada]

I've got my iSport set with profiles for two bikes. I'm getting some numbers that look a bit flaky on profile 2, and could use some feedback. I got good tilt and wind offsets, started with est CDA and default crr numbers, did good cal rides on each bike, then did good coastdowns. Cal rides and coastdowns were done on the same stretch of road, back to back. Here's what I got:

Profile 1
CST Aero: 0.332
CST Fric: 8.109
CRR: 86

Profile 2:
CST Aero: 0.493
CST Fric: 11.889
CRR: 130

The friction and crr numbers on profile 2 look way off. Just to isolate variables, I re-ran the CD's switching front wheels and had nearly identical results. Should I look at overhauling bike 2's rear wheel?

Thanks for any advice..!

[mds]

I have an isport and have been also working to get good results. Your higher Fric on profile 2 is consistent with its higher Crr. Fric is a function of weight, Crr and the component of tilt due to stem/fork flex. Can you switch rear wheels, do a couple more coast downs, and see if you see consistent differences? This might help indicate whether or not there is a rear wheel problem.

[voodoorada]

I spent some time yesterday chasing rolling resistance on bike 2. I disassembled the rear hub, and found that one of its four cartridge bearings is a bit gritty, and the adjusting nut was a bit too tight. A new set of Boca hybrid ceramics is on the way, and I got the right amount of play in the rear hub. New coast down results:

Profile 2
CST Aero: .549
CST Fric: 4.867
CRR: 49

I rode after the new adjustments, and the bike feels a lot snappier than before...

Now, looking at profile 1, I'm going to check my other bike's hubs a bit more closely.