Calibration Procedure Check

[nigeld]

Hi, I've just got my iBike and trying to set it up correctly. I have a few questions. In the manual I though it says do coast downs then the Cal ride, but I see elsewhere on the forum people mention doing the Cal ride and then the coast downs. Which is correct? Does the order matter? I did the wind offset, tilt cal, 3 coast downs, and then the Cal ride. I got a wide range of fric numbers () on the coast downs. After the Cal ride the iBike calibrates itself, right? But there's also the procedure of downloading and analyzing in iBike 3, what does that add?

When I download my Cal ride and coast downs I get a grayed out screen saying "using cal ride calibration from unit for setting in iBike. Select Crr fixed or adjusted to analyze here." Which should I use? (Is this explained anywhere... I couldn't find anything on it.) I chose Adjusted (I think) and that ungrayed it and let me upload the cal processed cal ride back to the unit. The use setting from iBike has the tilt way off.







Wind looks strange on my ride out to the Cal ride, all headwind, then I did the Cal ride and the ride home looks much better, so obviously the iBike processes the Cal ride immediately and updates the onboard profile. I'm confident about each step, e.g. how to do the wind cal, or the coast downs, etc., not too sure how it all fits together though.

Any guidance and tips appreciated. Thanks. (Ride home after the Cal ride is attached.)

[nigeld]

In case anyone else is wondering about this...

Today I found a post that says cal ride is done *before* the coast downs. Well, luckily that's what I did last night. I did a 4 mile cal ride, and then the coast downs. My coasting check after the coast downs looked good too, +/- 5-8w. My power numbers now look reasonable, but I'd like a sanity check on these numbers, I don't know what the acceptable range is. BTW, my unit is mounted on the stem, wind port is about 1/2 inch behind the bar clamp.

Aero: 0.053
Fric: 8.224
Cda: 0.105
Crr: 0.0085
Wind Scaling: 0.508
Riding Tilt: -0.2
Cm: 1.020 (what is this?)

Thanks.

[R Mc]

Unless you weigh 110 pounds or less, the aero and cda numbers are still way off. (For reference, my cda on my time trial bike, with zipp 808s and an aero helmet, is around .229 and I'm 5'9" and 154 pounds).

That wind scaling number is on the low side too. Part of the problem might be that you have the unit mounted too far back on the stem, but something is off.

rolling resistance (crr) looks high, unless you did your c-ds on really rough pavement.

cm is a constant to account for drive-train inefficiencies.

[nigeld]

Thanks for the info R Mc, very helpful. I'm a little over 110 lbs, 5'6" and 150 lbs, so Cda should be a lot higher. The road was a normal, wheels are semi-aero (Rolfs) and tires are new Michelin Pro 3s. So I guess I should move the unit further forward and repeat the cal ride and CDs and see what I get.

My current mount, looks fairly clean:





Thanks again for the feedback!

[nigeld]

I have not changed anything and did a 63 mile ride today and the watts are reading low (probably the low Cda), obvious from the avg power of only 119w even though we did a lot of tempo. Tweaking Cda in iBike 3 overriding the 0.1045 with 0.275) gives a much more likely avg of 165w.

I'm considering doing a two step calibration process. Since my Cda is low and the Crr seems high, I'm thinking of using method 2 to get an accurate Cda (with Crr fixed at 0.0055). That will give me a pretty good Cda which I'll note. Then I'll try method 3 and see if I can get a reasonable number for Crr (and a Cda around the one from method 2). I can always override the Cda from method 3 with that determined in method 2 if it comes out significantly different using method 3. (I'm assuming there's no way to fix Cda at that given by method 2 and just doing CDs to determine Crr.)

Sound like a plan? Or is it unlikely to make any difference?

[coachboyd]

Hey Nigel,

It probably would make a difference as it seems like the unit is having a hard time pulling the cda from the crr numbers in the total forces slowing you down.

I took a look at the file and it looks like the wind setting is good, so I played around with the settings in your profile. If you would like, you can load this profile into your unit and that should give you great results from here on if you don't want to go through the calibration procedure again.

[nigeld]

Thanks Boyd, much appreciated! I will give this a try. Down the road I think I will do a few method 2 + 3 calibrations and see how establishing CdA and Crr separately works out, for now though, I just want to ride, so this is very helpful. Thanks again.

[nigeld]

Boyd, if I load this new profile into the iBike will I get exactly the same results as if I keep using my old profile and then apply this new profile to the ride file after the fact? I'm doing a comparison test of some equipment and I'm nearly done with equipment A, going on to B, so I want the results to be as accurate as possible. If uploading the new profile to the unit in is going to have some affect then I need to stick to the old one I used for equipment A and apply the new one to all the rides (A and B) after the fact.

BTW, profile looks great, applied to some rides, including a crit from last week, looks much better!

Thanks.