Dear all,
I have two bikes Kiron and Focus. Kiron winter bike with quite a few winter rides since getting iBike last year. Focus good weather carbon bike, just calibrated for iBike on Monday. It was a very windy day so after calibrating I went for a ride and recorded some of the best power results I had so far ( I know it's not much for some of you out there but I'm 48 and started serious cycling only a year ago ). Can I believe these watts? I'm attaching my ride and profiles of both bikes. On the Kiron on a calm day I achieve about 140w average on the same course and what feels like the same type of effort. Could it be the windy day that made me produce these figures on my other bike, or is something wrong with this profile? Sorry to be such an novice bore, but any comments would be much appreciated!
Can I believe these figures? Help please..
Can I believe these figures? Help please..
- Attachments
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- Kiron-060310-w-mdg.ibp
- (424 Bytes) Downloaded 216 times
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- iBike_Focus_ride_34_Miles.csv
- (1.61 MiB) Downloaded 220 times
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- Focus-220310-spring.ibp
- (331 Bytes) Downloaded 221 times
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lorduintah
- Posts: 648
- Joined: Fri Jan 11, 2008 9:37 am
- Location: Plymouth, MN
Re: Can I believe these figures? Help please..
There have been several discussions on how to "trust" your measured power - without having a DFPM on your bike.
Before running these you should make sure you do a tilt check and a wind calibration.
If you do a ride similar to the cal ride - out some distance, turn around and trace your path back to the beginning - the average speed and average wind should be close to one another - if your wind scaling is on target. Now you can check the CdA by coasting down a hill - at a starting speed of 20 mph. Put the iBike into the set up/Coast display. The value should be at or near zero while coasting and not pedaling. A large deviation from zero means your aerodynamic resistance is off - best to do another cal ride. Your estimate of CdA which you can get on the iBike and the actual CdA (from the cal ride - coast downs) should not be wildly different. On the same ride that you are checking wind scaling, you could also check your tilt - this should be around zero, also - because you have done the same route out as back, up and down even on a series of hills.
The Crr value - rolling resistance from your cal ride should probably be around 0.0055 to 0.008 - depends on you tires, wheels and road surface. This will typically not make a strong change in power.
Inspecting your cal ride plus coast-down analysis screen:
The speed plot portion of the screen - upper plot on the left - there should not be any significant section that shows a difference in corrected and uncorrected wind - any differences between the two lines should be consistent.
The bottom plot - elevation - will show an uncorrected line that may be consistently increasing or decreasing in value - riding up or down a hill for the major portion of the cal ride. If you rode something that was relatively flat then the corrected line should become roughly flat and overall the best line through all the regions of the corrected tilt will be horizontal. Your tilt calibration should usually be 0 to -.4, but this is only a guideline.
Go through all of this, more when John and Coach Boyd enhance the software in the future and you should have a pretty fair set of values for your profile that will give you realistic and believable watts.
Tom
Before running these you should make sure you do a tilt check and a wind calibration.
If you do a ride similar to the cal ride - out some distance, turn around and trace your path back to the beginning - the average speed and average wind should be close to one another - if your wind scaling is on target. Now you can check the CdA by coasting down a hill - at a starting speed of 20 mph. Put the iBike into the set up/Coast display. The value should be at or near zero while coasting and not pedaling. A large deviation from zero means your aerodynamic resistance is off - best to do another cal ride. Your estimate of CdA which you can get on the iBike and the actual CdA (from the cal ride - coast downs) should not be wildly different. On the same ride that you are checking wind scaling, you could also check your tilt - this should be around zero, also - because you have done the same route out as back, up and down even on a series of hills.
The Crr value - rolling resistance from your cal ride should probably be around 0.0055 to 0.008 - depends on you tires, wheels and road surface. This will typically not make a strong change in power.
Inspecting your cal ride plus coast-down analysis screen:
The speed plot portion of the screen - upper plot on the left - there should not be any significant section that shows a difference in corrected and uncorrected wind - any differences between the two lines should be consistent.
The bottom plot - elevation - will show an uncorrected line that may be consistently increasing or decreasing in value - riding up or down a hill for the major portion of the cal ride. If you rode something that was relatively flat then the corrected line should become roughly flat and overall the best line through all the regions of the corrected tilt will be horizontal. Your tilt calibration should usually be 0 to -.4, but this is only a guideline.
Go through all of this, more when John and Coach Boyd enhance the software in the future and you should have a pretty fair set of values for your profile that will give you realistic and believable watts.
Tom
Re: Can I believe these figures? Help please..
Thanks for taking the time to clarify this for me Tom. I've copied your notes and will put my bike through the procedures you describe to check things out. On that cal ride I did, iBike was in the car and I did not wait for it to "aclimatise" itself to external temperature. Also it was very windy on that day...Do you recommend performing cal rides, and coast down tests in calm conditions?
Thanks, Dusan
Thanks, Dusan
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lorduintah
- Posts: 648
- Joined: Fri Jan 11, 2008 9:37 am
- Location: Plymouth, MN
Re: Can I believe these figures? Help please..
Dusan -
That is the general consensus here. Anything up to 5 mph is ideal. But I have found that you can do a fairly good job if the gusts are under 10 mph. The CDs seem to work better for me if I also do them into the wind/breeze. Keep in mind that the suggested course of action on the CDs is to find the similar road surface you normally ride on, little to no traffic. Ideal is to find a stretch that may have a little bowl shape - you start by going downhill to make it easier to get to 20 mph and then uphill on a gentle incline to slow down the coasting. If you cannot do that then a flat to slightly uphill stretch will work fine.
I would ride with your current setup for a little while - get used to the values you are seeing as you traverse different conditions - maybe even find a better spot for the cal ride and CDs if you get lucky. I went through about five locations before I found one that was to my liking - very low traffic and consistent wind patterns with a length of road allowing me to crank it up and coast. No rush and I do not mean to imply that where you did your cal ride and so on had any issues.
The latest documentation from velocomp describes the phases of calibration from minimum to some of the fine tuning you can do. Soon, there will also be some new features in the software to help even more to discriminate the details of the calibration data.
Tom
That is the general consensus here. Anything up to 5 mph is ideal. But I have found that you can do a fairly good job if the gusts are under 10 mph. The CDs seem to work better for me if I also do them into the wind/breeze. Keep in mind that the suggested course of action on the CDs is to find the similar road surface you normally ride on, little to no traffic. Ideal is to find a stretch that may have a little bowl shape - you start by going downhill to make it easier to get to 20 mph and then uphill on a gentle incline to slow down the coasting. If you cannot do that then a flat to slightly uphill stretch will work fine.
I would ride with your current setup for a little while - get used to the values you are seeing as you traverse different conditions - maybe even find a better spot for the cal ride and CDs if you get lucky. I went through about five locations before I found one that was to my liking - very low traffic and consistent wind patterns with a length of road allowing me to crank it up and coast. No rush and I do not mean to imply that where you did your cal ride and so on had any issues.
The latest documentation from velocomp describes the phases of calibration from minimum to some of the fine tuning you can do. Soon, there will also be some new features in the software to help even more to discriminate the details of the calibration data.
Tom
Re: Can I believe these figures? Help please..
Tom, thanks, It's what I suspected, so I'll wait for some calmer conditions. My regular training ground is higher than surrounding terrain and fairly open so it does tend to get blasted by winds on occasions. As you say I'll keep the current profile until I find the right moment to redo cals.