I’m a new IBike user and new to this forum. Although the installation and calibration procedures were surprisingly simple, complications began when I started using the Process Calibration Ride utility. There are quite a few manuals and hundreds of posts in this forum, so it is very possible I missed it, but I wish there were a single location (or manual) that explains in detail how the calibration ride and coast-downs interact with profile parameters.
Wheel circumference and total weight are easy parameters to determine, so no problems there. There’s some potential for error with Tilt and Wind cal, but they’re pretty easy to do so this shouldn’t be an issue (as long as you’re careful).
From there, you have to read between the lines.
1)If I understand things correctly, my first IBike calibration ride (new out of the box) is done using Crr and CdA from what was determined by “EST AERO” in the “FAST START”. Does this really matter anyway? The calibration ride is to determine wind scaling and tilt which doesn’t need CdA and Crr… correct?
2)There’re a lot of conflicting posts on what a good coast location is… bowl shaped, uphill, one way only, both directions, same section of road, varying sections of road, 15-30 seconds, what Crr to use, etc. Here’s where a single point of reference authorized by Velocomp would be nice so new users know exactly what “correct” is. (Again, forgive me if this already exists and I missed it)
The Process Calibration Ride utility is a powerful tool, but using it requires knowledge beyond what is obvious.
3)The Coast-Down section allows certain coast-downs to be removed. What determines a “bad” coast-down? If it’s as simple as the one that doesn’t look like the others, to what magnitude? I suspect
4)There are 3 choices in the Crr pull-down. The resulting CdA from using “setting in bike” or “adjusted” is pretty significant. Which gives me the most accurate profile and why?
5)I’ve read posts that say after a good calibration ride, coast-downs, and profile from the Process Calibration Ride utility… the Crr should be changed yet again because the coast down Crr may not reflect what you will encounter on normal rides. Another change? And to what value?
I’ve found the IBike to be a great device, but like any computer, garbage in = garbage out. I’m trying to educate myself on what experienced users like Boyd look for when trying to determine what is wrong (or right) with a profile. Any feedback would be appreciated…
Thanks,
JRB
Calibration Profiles
Re: Calibration Profiles
This is a really good set of questions. I have a request of sorts to the velocomp folks to add on to it, and then a response to one part of your post:
Request: I think it's time for a thorough scrubbing of the manuals to reflect what's going on with fw4. There's much confusion about the best way to do coast-downs, for example--and there is no definitive explanation in the manual. There might be on the video, but it would just take one sentence in the manual to clarify best c-d practice. It might also be time for a scrubbing/archiving of the forum.
Response: As for changing crr after coast-downs and calibration rides. Here's my scenario: I do coast-downs on a really smooth section of asphalt--I know the crr is somewhere between .04 and .045 (depending on wheels). Most of the roads I actually ride on are varying degrees of nasty chip-seal with crrs ranging from .06 to .08. So after the coast-down process is done, I change the crr to .072 to reflect what I'll be riding. If you do coast-downs with the wrong crr you get cruddy aero numbers; if you ride rougher roads than what you did your coast-downs on, you get skewed results. At least, that's my theory.
Request: I think it's time for a thorough scrubbing of the manuals to reflect what's going on with fw4. There's much confusion about the best way to do coast-downs, for example--and there is no definitive explanation in the manual. There might be on the video, but it would just take one sentence in the manual to clarify best c-d practice. It might also be time for a scrubbing/archiving of the forum.
Response: As for changing crr after coast-downs and calibration rides. Here's my scenario: I do coast-downs on a really smooth section of asphalt--I know the crr is somewhere between .04 and .045 (depending on wheels). Most of the roads I actually ride on are varying degrees of nasty chip-seal with crrs ranging from .06 to .08. So after the coast-down process is done, I change the crr to .072 to reflect what I'll be riding. If you do coast-downs with the wrong crr you get cruddy aero numbers; if you ride rougher roads than what you did your coast-downs on, you get skewed results. At least, that's my theory.
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lorduintah
- Posts: 642
- Joined: Fri Jan 11, 2008 9:37 am
- Location: Plymouth, MN
Re: Calibration Profiles
There is nothing major in using a Crr value that is fixed - R Mc ( are you missing a "0"? like 0.0045 not 0.045). The Crr is not considered a dynamic value in the models for power - it is a constant add on of power due to road type, wheels, hubs - anything that directly connects your bike to the road and affects the rotational movement of those parts. So if you just happen to have a brake pad rubbing or a dry wheel bearing the Crr will be higher. You might even see changes to Crr as you change the tire pressure and can see a difference by changing the tires you use while at the same pressure. The type of road/path surface will affect this, too. But just keep in mind that Crr typically will have a small impact on power - the faster you go the less it contributes, because it is a constant factor in the dynamics of motion.
Tom
Tom
Re: Calibration Profiles
"1)If I understand things correctly, my first IBike calibration ride (new out of the box) is done using Crr and CdA from what was determined by “EST AERO” in the “FAST START”. Does this really matter anyway? The calibration ride is to determine wind scaling and tilt which doesn’t need CdA and Crr… correct?"
With FW 400+ I think of the calibration procedure as good/better/best:
Good: Perform the Fast Start procedure. This will provide a decent result, particularly at slower speeds.
Better: In addition to Fast Start, perform a Cal Ride. This likely will result in a solid accuracy improvement at higher speeds (18mph+) compared to the "Good" calibration, and will also allow accurate wind speed measurements.
Best: In addition to the Cal Ride, perform coast downs and process with iBike 3. Depending on your riding style, this will give a minor-to-medium improvement over the Better calibration.
When you use the Fast Start procedure your CdA and Crr are estimated by the Fast Start screens; the firmware "backs in" to the corresponding estimated aero and fric coefficients used by the iBike. Generally, these estimated aero and fric coefficients are reasonably accurate, particularly when the Cal Ride is done.
To get the most accurate aero and fric coefficients, the cal ride and coast downs need to be done. The coast down actually measures aero and fric drag. The FW then calculates the CdA and Crr associated with the measured drag coefficients.
"2)There’re a lot of conflicting posts on what a good coast location is… bowl shaped, uphill, one way only, both directions, same section of road, varying sections of road, 15-30 seconds, what Crr to use, etc. Here’s where a single point of reference authorized by Velocomp would be nice so new users know exactly what “correct” is. (Again, forgive me if this already exists and I missed it)"
Boyd may have more words to add but my experience is that the key to a good Cal Ride and good Coast Downs is to do just what the instructions say:
1) Make sure you've done a Cal Wind and Tilt cal prior to Cal Ride and Coast downs
2) Do the Cal Ride before doing the optional coast downs
3) Pick an uncrowded road without gusty winds. Remember: traffic causes wind gusts!
4) When doing coast downs sure the road is level to uphill and for coast downs make sure to ride into the wind
We've learned the hard way that it is IMPOSSIBLE to predict all the variations in road quality, traffic, weather conditions that occur. So, there is no "single point of reference authorized by Velocomp". Instead, we try to provide customers the information they need regarding the operational principles of the iBike so they can make informed judgments regarding their local conditions.
Above all, please remember that ANY iBike owner will get good results even with the most basic calibrations. All of the extra stuff is for people who want to "dial-in" their unit to the maximum extent possible.
"3)The Coast-Down section allows certain coast-downs to be removed. What determines a “bad” coast-down? If it’s as simple as the one that doesn’t look like the others, to what magnitude? I suspect"
The iBike 3 software automatically figures out the quality of each coast down and assigns an appropriate weighting. The primary factor affecting coast down quality is wind gusts, generally caused by passing traffic.
The reason for the "Remove" button is because, sometimes, there are old coast downs in the ride memory, as denoted by a different date. Those should be removed prior to analysis.
"4)There are 3 choices in the Crr pull-down. The resulting CdA from using “setting in bike” or “adjusted” is pretty significant. Which gives me the most accurate profile and why?"
Remember the the "setting in bike" is an ESTIMATE, whereas your "adjusted" is based on actual data. If you have the time and care to do coast downs, then use the actual data.
"5)I’ve read posts that say after a good calibration ride, coast-downs, and profile from the Process Calibration Ride utility… the Crr should be changed yet again because the coast down Crr may not reflect what you will encounter on normal rides. Another change? And to what value?"
If you have done careful tilt, wind cal, and coast downs, then I would not adjust your data; what you've MEASURED is the best data for you and your bike, on the road type where you have done your calibrations. If after your coast downs you ride on significantly different roads then your Crr will change up or down, but your CdA will be about the same. R Mc does a good job of describing how to make these changes.
We're trying to update the manuals now to reflect the improvements of FW 4.02. It is a daunting job but I agree that we have an obligation to keep things current.
Please keep in mind that some users have detailed questions such as are reflected in these posts, but most users do NOT want this level of detail. As is, our primary instruction manual is 74 pages long! Instead, we leave some of these advanced topics to the forum...
We will be releasing a new set of videos this Fall that reflect all the FW changes.
With FW 400+ I think of the calibration procedure as good/better/best:
Good: Perform the Fast Start procedure. This will provide a decent result, particularly at slower speeds.
Better: In addition to Fast Start, perform a Cal Ride. This likely will result in a solid accuracy improvement at higher speeds (18mph+) compared to the "Good" calibration, and will also allow accurate wind speed measurements.
Best: In addition to the Cal Ride, perform coast downs and process with iBike 3. Depending on your riding style, this will give a minor-to-medium improvement over the Better calibration.
When you use the Fast Start procedure your CdA and Crr are estimated by the Fast Start screens; the firmware "backs in" to the corresponding estimated aero and fric coefficients used by the iBike. Generally, these estimated aero and fric coefficients are reasonably accurate, particularly when the Cal Ride is done.
To get the most accurate aero and fric coefficients, the cal ride and coast downs need to be done. The coast down actually measures aero and fric drag. The FW then calculates the CdA and Crr associated with the measured drag coefficients.
"2)There’re a lot of conflicting posts on what a good coast location is… bowl shaped, uphill, one way only, both directions, same section of road, varying sections of road, 15-30 seconds, what Crr to use, etc. Here’s where a single point of reference authorized by Velocomp would be nice so new users know exactly what “correct” is. (Again, forgive me if this already exists and I missed it)"
Boyd may have more words to add but my experience is that the key to a good Cal Ride and good Coast Downs is to do just what the instructions say:
1) Make sure you've done a Cal Wind and Tilt cal prior to Cal Ride and Coast downs
2) Do the Cal Ride before doing the optional coast downs
3) Pick an uncrowded road without gusty winds. Remember: traffic causes wind gusts!
4) When doing coast downs sure the road is level to uphill and for coast downs make sure to ride into the wind
We've learned the hard way that it is IMPOSSIBLE to predict all the variations in road quality, traffic, weather conditions that occur. So, there is no "single point of reference authorized by Velocomp". Instead, we try to provide customers the information they need regarding the operational principles of the iBike so they can make informed judgments regarding their local conditions.
Above all, please remember that ANY iBike owner will get good results even with the most basic calibrations. All of the extra stuff is for people who want to "dial-in" their unit to the maximum extent possible.
"3)The Coast-Down section allows certain coast-downs to be removed. What determines a “bad” coast-down? If it’s as simple as the one that doesn’t look like the others, to what magnitude? I suspect"
The iBike 3 software automatically figures out the quality of each coast down and assigns an appropriate weighting. The primary factor affecting coast down quality is wind gusts, generally caused by passing traffic.
The reason for the "Remove" button is because, sometimes, there are old coast downs in the ride memory, as denoted by a different date. Those should be removed prior to analysis.
"4)There are 3 choices in the Crr pull-down. The resulting CdA from using “setting in bike” or “adjusted” is pretty significant. Which gives me the most accurate profile and why?"
Remember the the "setting in bike" is an ESTIMATE, whereas your "adjusted" is based on actual data. If you have the time and care to do coast downs, then use the actual data.
"5)I’ve read posts that say after a good calibration ride, coast-downs, and profile from the Process Calibration Ride utility… the Crr should be changed yet again because the coast down Crr may not reflect what you will encounter on normal rides. Another change? And to what value?"
If you have done careful tilt, wind cal, and coast downs, then I would not adjust your data; what you've MEASURED is the best data for you and your bike, on the road type where you have done your calibrations. If after your coast downs you ride on significantly different roads then your Crr will change up or down, but your CdA will be about the same. R Mc does a good job of describing how to make these changes.
We're trying to update the manuals now to reflect the improvements of FW 4.02. It is a daunting job but I agree that we have an obligation to keep things current.
Please keep in mind that some users have detailed questions such as are reflected in these posts, but most users do NOT want this level of detail. As is, our primary instruction manual is 74 pages long! Instead, we leave some of these advanced topics to the forum...
We will be releasing a new set of videos this Fall that reflect all the FW changes.
John Hamann
Re: Calibration Profiles
We've just released FW 402 and have scrubbed all of our instructions to reflect the changes. New instructions are available from the Installation Tutorials section of the forum
John Hamann
Re: Calibration Profiles
As suggested in preceding posts, where and when is a Crr change made for future rides?
To create an "out of the box" situation, I flipped the battery over to reset my iBike. I set “EST AERO” to "YES – HOODS" and rode 40 minutes to the calibration site. The displayed data on the way out looked pretty good.
Conditions were virtually perfect - little or no wind. I did a careful wind and tilt cal, then the calibration ride. Exactly one car passed me… that's it. Conditions were so good for coast-downs that I packed in over 10. I figured I better take advantage of the situation. Here's what I found after I downloaded my data:
1) Looking at my ride to the site, I see that CdA = 0.368 and Crr = 0.0073. The manual says that by default, a fixed Crr value of 0.0055 is used unless you set "EST FRIC" to "NO". I only entered “FAST START” data, so why was Crr = .0073? The date/time was reset to 12:00AM 6/10/2009 so I assume I did the reset correctly.
2) Looking at my ride home AFTER the cal ride and coast-downs, I see CdA = 0.200 and Crr = 0.0073. This created some pretty unrealistic power values on the way home. Is this normal?
3) I now use the Process Calibration utility. The window opens up with Crr set to "setting in bike" with CdA = 0.245 and Crr = 0.0073. Why is the CdA not 0.368 (the setting in the pre-calibration ride data) or 0.200 (the setting in the post-calibration ride data)? Where did 0.245 come from?
4) Now I’m unsure what to do. Should I be concerned that the original Crr wasn’t 0.0055?
5) Should I set “EST FRIC” to “YES” and do the whole thing over? (Doubtful I’ll see conditions like that again though...)
6) Should I go with what I got and just save the profile with “Crr adjusted”?
7) Now… how do I change the Crr for future rides as suggested in earlier posts?
- Do I NOT save the profile as “Crr adjusted” but rather as “Crr fixed” with Crr = 0.007? This of course maintains tilt, but alters Fric.
- OR, save the profile as “Crr adjusted” then change Crr to 0.007 in “Advanced Profile Settings…” of Edit Profile. This alters riding tilt AND Fric where as the other option only altered Fric.
- OR, save the profile as “Crr adjusted” then change Crr to 0.007 MANUALLY in the "EST FRIC" of the "RACR" settings.
Which is the correct way to do this?
Thanks for any input…
To create an "out of the box" situation, I flipped the battery over to reset my iBike. I set “EST AERO” to "YES – HOODS" and rode 40 minutes to the calibration site. The displayed data on the way out looked pretty good.
Conditions were virtually perfect - little or no wind. I did a careful wind and tilt cal, then the calibration ride. Exactly one car passed me… that's it. Conditions were so good for coast-downs that I packed in over 10. I figured I better take advantage of the situation. Here's what I found after I downloaded my data:
1) Looking at my ride to the site, I see that CdA = 0.368 and Crr = 0.0073. The manual says that by default, a fixed Crr value of 0.0055 is used unless you set "EST FRIC" to "NO". I only entered “FAST START” data, so why was Crr = .0073? The date/time was reset to 12:00AM 6/10/2009 so I assume I did the reset correctly.
2) Looking at my ride home AFTER the cal ride and coast-downs, I see CdA = 0.200 and Crr = 0.0073. This created some pretty unrealistic power values on the way home. Is this normal?
3) I now use the Process Calibration utility. The window opens up with Crr set to "setting in bike" with CdA = 0.245 and Crr = 0.0073. Why is the CdA not 0.368 (the setting in the pre-calibration ride data) or 0.200 (the setting in the post-calibration ride data)? Where did 0.245 come from?
4) Now I’m unsure what to do. Should I be concerned that the original Crr wasn’t 0.0055?
5) Should I set “EST FRIC” to “YES” and do the whole thing over? (Doubtful I’ll see conditions like that again though...)
6) Should I go with what I got and just save the profile with “Crr adjusted”?
7) Now… how do I change the Crr for future rides as suggested in earlier posts?
- Do I NOT save the profile as “Crr adjusted” but rather as “Crr fixed” with Crr = 0.007? This of course maintains tilt, but alters Fric.
- OR, save the profile as “Crr adjusted” then change Crr to 0.007 in “Advanced Profile Settings…” of Edit Profile. This alters riding tilt AND Fric where as the other option only altered Fric.
- OR, save the profile as “Crr adjusted” then change Crr to 0.007 MANUALLY in the "EST FRIC" of the "RACR" settings.
Which is the correct way to do this?
Thanks for any input…
Re: Calibration Profiles
I am trying to find this "Process Calibration Utility" - can someone point me in the right direction? Also, great questions...look forward to the answers...
Cheers!
JR
Cheers!
JR
Re: Calibration Profiles
It's the window (in iBike 3) that pops-up when you select Profiles>Download Coast-downs & Calibration Ride...
Re: Calibration Profiles
Gotcha...no worries...just didn't know what it was called - but thanks - I use it all the time...
Cheers!
JR
Cheers!
JR