iAero calibration ride / coast downs / profile

[rstrom]

For the past few months I've been working off a profile that Coach Boyd (pretty sure) modified for me. I've since switched bikes and I'm wanting to create a new profile for this bike. Besides I really, really want to learn how to properly create and identify a good profile.

So .... on Friday I had the day off and I dedicated a good bit of time doing two calibration rides (one in each profile) and doing numerous coast downs (19 of them). I then chose what I thought was the best of the two profiles and applied the coast downs to the calibration ride (Crr adjusted). With this I thought that I had finally created a good profile on my own. But now I'm not sure as the past two rides (Saturday maybe, but Sunday and Monday definitely) seem to me like the numbers that I'm seeing are low.

An example would be that on a ride today I was going down a hill (average 1.3% downhill grade with a 1 mph tailwind) but pushing it moderately (average speed 20.7; max speed 29.7) and my average watts were 84 (1hr 57min - 2hr 7min - lap 8). It sure felt like I was working harder than that ...

So I was hoping that someone out there would be gracious enough to take a look at my calibration ride file; the attached ride file from today that I reference above; and the attached profile and let me know if the calibration ride and the resulting profile are good and if not why.

[Velocomp]

I looked at your files.

You did your first Cal Ride on May 28, followed immediately thereafter by 19 coast downs (!), followed immediately thereafter by yet another Cal Ride.

Since the second Cal Ride was performed after the coast downs, I did not use that Cal Ride. Remember: the instructions say that coast downs should be done AFTER the Cal Ride.

The coast down information you have is remarkably consistent. Your measured CdA is 0.331 and your Crr is 0.0033. I'm estimating your body weight at about 160 pounds and height at about 5' 9", so the CdA number is in line with our Est CdA algorithm. Crr seems a bit low but I don't have details about your bike and wheels. WSF is .741 and Riding Tilt is -0.4%, both reasonable

What's curious is that your May 31 ride uses a profile different from the one you created on May 28. Why?

The May 31 ride has Boyd's profile with substantially higher CdA (0.37) and Crr (0.0058). WSF was comparable (.702) and Riding Tilt was the same (-0.4%).

Since you say you switched bikes, Boyd's old profile doesn't really apply to your new bike.

Your May 28 profile is backed by a ton of coast downs showing consistent results. Furthermore, your measured CdA is very consistent with the Est CdA algorithm. So, I would adopt your May 28 profile as the go-forward profile for your training. I've attached your profile.

Here's the bad news: your May 31 file was done with Boyd's profile. That same ride, with your May 28 profile, will cause your watts to drop, because your CdA and Crr are both lower.

Looking at your watts and HR information for the downhill you mention, I don't see anything terribly distressing. It looks like soft pedaling, and your HR drops, indicating that your work effort was decreasing.

What's important now is to get the new profile loaded in to your bike and to use it consistently for your training.

[rstrom]

OK - looks like I am able to finally get some good calibrations going and coast downs going here!!! This definitely makes me happier and more confident in using the iBike.

With regards to the second CalRide, this was done under a second profile within a relatively short time period of both the first CalRide and the Coast Downs, is this still not valid even given the fact that it was done under the second profile?

Your measured CdA is 0.331 and your Crr is 0.0033. I'm estimating your body weight at about 160 pounds and height at about 5' 9", so the CdA number is in line with our Est CdA algorithm. Crr seems a bit low but I don't have details about your bike and wheels. WSF is .741 and Riding Tilt is -0.4%, both reasonable

Yes, I'm about 160lbs and 5'9" (you're scaring me)

Current Bike is a Cannondale CAAD 9 with Dura-Ace and Ksyrium Elite wheels.

What's curious is that your May 31 ride uses a profile different from the one you created on May 28. Why?

I honestly don't remember for sure but I think that I applied a different profile to see what it looked like (since I was doubting the numbers).

Here's the bad news: your May 31 file was done with Boyd's profile. That same ride, with your May 28 profile, will cause your watts to drop, because your CdA and Crr are both lower.

I know, believe me I know

So now it's time for another question or two ...

The CalRide and Coast Downs that were previously sent were done in my neighborhood on some pretty smooth pavement.

Much of my riding is done on some significantly rougher chip sealed roads. So, on Tuesday (6/1/2010) I went over to the area where I do a lot of riding (it also represents the same type of road surfaces lots of my other riding is done on) and performed another CalRide - this time at least 4 miles - and then did more Coast Downs. The CalRide was performed on variable terrain and the Coast Downs were performed on an uphill.

The numbers from the CalRide pre-application of the Coast Downs are:

Aero - 0.210
Wind Scaling - 0.786
CdA - 0.267
Fric - 12.326
Riding Tilt - negative 1.0
Crr - 0.0051
Cal Weight - 183

The numbers from the CalRide post-application of the Coast Downs are:

Aero - 0.259
Wind Scaling - 0.786
CdA - 0.330
Fric - 10.504
Riding Tilt - negative 1.1
Crr - 0.0019
Cal Weight - 183

(Files attached)

So, what are your thoughts on the smooth road vs. the rough roads?

How do the CalRide and Coast Downs look for this effort?

Thanks very much !!!

Robert

RStrom_CalRide_2010-06-01.zip

CalRide and Coast Downs performed on rough chip sealed roads on 6/1/2010

(46.79 KiB) Downloaded 365 times

[rstrom]

I forgot to include the calibration ride / coast down file

[coachboyd]

The only difference between smooth and rough roads should be in your crr (rolling resistance). Your cda and aero and wind scaling should all stay the same.
Rather than going through the whole cal ride and coastdown process again, this is where you can manually edit a profile.
All you have to do is in your profile information hold the riding tilt steady and change the crr. The difference between smooth and rough roads should take you from the .0033 that you saw to about .0055. When you change your crr in your profile the friction will also change to a new amount.

Overall, it looks like if you used the estimated crr and cda function in the iBike you could have avoided all coastdowns and just have done an out and back ride.

[rstrom]

Thank you!!