Which calibration ride is better?

[gerrard]

I was getting some weird wattages when I was out riding today - things like:
- 200 watts when I was going downhill with a tail wind (normally see 0-40)
- 200-250 watts on the flat when my perceived effort was much less

These readings never seemed to hang around for long, but overall I felt like the numbers were higher then I would normally see. I spent ages trying to work out what it was. I did new tilts, cal winds, and even a new calibration ride but couldn't nail it. I'm now wondering if the last few weeks of work on the bike are starting to show and my threshold has moved. Off to test that next opportunity I can to find out for sure...

So amongst all that I got a new cal ride and the data was a bit different from the last one I did. Here are the numbers:

original new
aero 0.409 0.341
wind scaling 1.103 0.922
cda 0.370 0.370
fric 5.170 6.932
tilt -0.2 -0.4
crr 0.0039 0.0039

original cal ride done on a flat smooth(ish) road. New cal route had a few small undulations and a much rougher surface which is more reflective of what I usually ride on.

So any problems in these numbers, or would I expect to see much difference in readings due to the difference in the two calibrations?

Thanks
Gerrard

[rcmaps]

Appears that your crr is a bit low - smooth asphalt is normally 0.055 (ibike's default value), so unless you have a very good wheelset with smooth running and quality tyres (eg Continental black chilli compound etc like Grandprix Attack Force) at good pressures (probably 100psi+), I would question that 0.0039. I get around 0.0060 around my calibration course in NZ - which is around up to 5 km or so with a combination of some rough chip seal and a short stretch (100m) of relatively smooth asphalt. However, most country roads here are typically very rough chip seal - crr of 0.006-0.007 or so.
Change in tilt value can be due to different hand positions (and to a lesser extent change in tyre pressures) during both rides but as it didn't differ too much, it's probably ok.

I was getting some weird wattages when I was out riding today - things like:
- 200 watts when I was going downhill with a tail wind (normally see 0-40)
- 200-250 watts on the flat when my perceived effort was much less

Did you download and check your ride file in IBike software - Analyze Route - Show Tilt Plot ? Sometimes the tilt gets messed up during your ride and the software can correct it. If you think it's too high, it's likely that the original ride file's tilt plot (green line) has an upward sloping curve that should be corrected in the software to a flat line. Your power readings should then correspondingly decrease as well.
If this isn't the case, then congrats - you must have increased your wattage!

[lorduintah]

IN the analysis - did you allow the Crr to change or did you use the value in the iBike?

I would double check that and then there are those who will want you to upload your calibration ride files for further tweaking.

Tom

[gerrard]

rcmap - I'm in Wellington - where are you?

The crr is just what ibike gives me. It seemed low but I didn't know what was normal for our roads here. I'm running cheap wheels and tires so think it should be higher. I was wondering that's why my fric value went up between the two rides? I can't manually edit crr - that field is greyed out in my profile.

I just did the show tilt plot on and it doesn't look crazily off to me. Differences in the numbers are pretty minor (see attached). Also I don't see an option to accept the tilt plot changes. Is that just factored into the "accept" for the analyse route?

Also attached are the two cal rides (original and new) in case anyone wants to / can go looking in those for more info.

Cheers
Gerrard

[rcmaps]

Hi Gerrard, I'm in Hamilton.
You should be able to edit most values in your profile in the ibike software - eg to over ride crr or any other values.
Profiles - Edit Profile

You need to untick some values to edit other values. For example, if crr is greyed out, click on Friction button which will turn it to "Hold" and then "crr" will then turn to "Adjust", you can then adjust the crr value.

It's probably not advisable to adjust tilt as the calibration ride figures that out correctly for you most of the time. The only time that tilt can be off is if you change the position of the mount, change your physical setup like handlebar stem length or tilt your handlebars up or down obviously.

[gerrard]

Thanks. I'll give it a go