Jagged tilt lines. Can the ride be salvaged?

[nreimche]

Jagged tilt lines. Can the ride be salvaged? Are my watts accurate if the tilt line is straight, but jagged? Or what if the tilt line swoops, but levels out? Will the watts be accurate where the line is straight? I can attach a ride if need be. Thanks.

[travispape]

Jagged tilt lines. Can the ride be salvaged? Are my watts accurate if the tilt line is straight, but jagged? Or what if the tilt line swoops, but levels out? Will the watts be accurate where the line is straight? I can attach a ride if need be. Thanks.

Yeah, post the file and we'll have a look.

[nreimche]

Cool! Here is the file(s). Thanks too!

[travispape]

Cool! Here is the file(s). Thanks too!

Yes, I think the ride can be salvaged. The tilt is a problem in this ride, but that is something that iBike2 can do a good job repairing, as you have already done in your 28 mi ride. If you are riding a road bike, it looks like both your CdA and your Crr are too high. For this ride, you can go into "Tweak CdA, Crr, & Cm..." window and change CdA to something more like 0.42 m^2 (a guess based on your riding on the hoods with winter clothes) and Crr to 0.006 (typical for road tires).

It looks like the first thing to work on might be your mount. Like you said, the tilt changed in both directions through the course of your ride. The iBike needs to stay at the same tilt throughout the ride, so make sure there is no chance bumps on the road can knock it around.

After that, be sure to get a good set of coastdowns with a 4 mi out & back cal ride to create a good profile.

Also, make sure you are using the latest versions of the FW and iBike2 (iBike3 is going to be posted soon) software.

Travis

[nreimche]

So if the cda and crr are corrected will the watts still be off somewhat? How much 'off'' would be a good estimate? Another question is: Even, if I use a good/accurate profile w/ that ride (I think I have one profile that gives me realistic wattages compared to Kinetic trainer and power meter, lol.) (it was a while back and I don't remember what I was wearing or riding at the time, either! Anyways...), should I get accurate data second for second or would the averages, only, be accurate? For instance where the jagged line slopes down for that, lets say minute of ride time would the watts be underreported, and where the line goes upward, again this is after an auto analisis, will the watts be overreported? I'll be honest, I do have an oversized mount on a standard size T bar w/ several shims and athletic tape coming from the stem, but I got third place in the Cat 5 Az state time trial championships. That explains the slight tilt movements.

Were the Gen 1s as accurate as the Gen 2s? I realized I have a Gen 1 Ibike pro, and it has been quite fussy. Does the Generation type have anything to do with it?

[nreimche]

Oh yeah, thanks Travis. That does answer some of my question. I see it can be salvaged and I need to tweak the cda and crr and secure the mount better. Regarding a tilt issue as before, now what if a have a power file w/ the corrected tilt line sloping downward then going level for most of the ride, will the watts where the tilt line is straight going to be corrected, after the analysis?

[travispape]

So if the cda and crr are corrected will the watts still be off somewhat? How much 'off'' would be a good estimate? Another question is: Even, if I use a good/accurate profile w/ that ride (I think I have one profile that gives me realistic wattages compared to Kinetic trainer and power meter, lol.) (it was a while back and I don't remember what I was wearing or riding at the time, either! Anyways...),

The Watts will be as accurate as the CdA and Crr, so the next thing to work on is getting a good calibration.

should I get accurate data second for second or would the averages, only, be accurate?

Are those my only two choices? The truth is more towards the middle. No two power meters on the market will completely agree with each other on time scales of the pedal cadence (roughly 1 s) due to differences in technology, sampling rate, recording rate, aliasing, filtering, etc. It takes a few seconds of integration to have a good bead on the power measurement.

For instance where the jagged line slopes down for that, lets say minute of ride time would the watts be underreported, and where the line goes upward, again this is after an auto analisis, will the watts be overreported? I'll be honest, I do have an oversized mount on a standard size T bar w/ several shims and athletic tape coming from the stem, but I got third place in the Cat 5 Az state time trial championships. That explains the slight tilt movements.

The shims and tape are definitely a problem. If you want good power data, you need a better mount job.

Were the Gen 1s as accurate as the Gen 2s? I realized I have a Gen 1 Ibike pro, and it has been quite fussy. Does the Generation type have anything to do with it?

GenII has new HW that improves performance on rough roads. GenIII has new HW, FW, and calibration that will make the iBike more forgiving if you mess up the tilt cal, wind offset cal, or if you have mild mount problems. I would say your mount problems are a tad worse than mild.

Regarding a tilt issue as before, now what if a have a power file w/ the corrected tilt line sloping downward then going level for most of the ride, will the watts where the tilt line is straight going to be corrected, after the analysis?

With regard to the tilt calibration (and assuming good drag coefficients in your profile), the power should be accurate everywhere post-analysis. Where the green line is horizontal in the graph, the power reported as seen while riding was accurate too.

Travis

[nreimche]

About the sec by sec analzsis I guess I was asking so I can understand the Ibike better(better understanding=less frustration or time, of course ). This is the last question, then I think that will be it: After I change the estimated cda(.42) and crr(.006) should I run another, auto, analysis?

[travispape]

About the sec by sec analzsis I guess I was asking so I can understand the Ibike better(better understanding=less frustration or time, of course ). This is the last question, then I think that will be it: After I change the estimated cda(.42) and crr(.006) should I run another, auto, analysis?

There's no need to do it again. Once you do the auto analysis, it remains in effect unless you pick the menu item to undo the analysis.

By the way, those drag number I gave you were just guesses. Hopefully you'll get some good weather for redoing your coastdowns & 4 mi O & B soon. Once you do get a good profile, note that you can apply it to your old rides by using the menu item "Tools -> Switch Profile After-the-Ride". And once you have a good profile, you can ride with it for weeks or months without worry about it as long as you don't change anything significant to your aero or rolling drag.