The when & how of using wind offset analyze feature

[leonsrocketcar]

When should one use the WO analyze feature in IB2? For instance, say I forgot to set my wind offset before the ride, but aftwards use the weather underground site for wind speeds during my ride time period. Do I use the wind offset or the avg ground speed box to insert the value from WU? The example in the software manual is a simple out and back so I am not sure how to use this feature as I don't do many OBs. Seems to me that you want the blue bar to read what the WU says wind speed is measured. Just not sure the purpose or how to get ground wind (green bar).
Kevin

[Site_Admin]

I may be wrong, but here's the way I do it...

1) Calibrate wind and tilt before heading out on your ride with the head unit.
2) Download and make sure you have the proper Profile connected to that file. This is pre-analysis.
3) Check the proper airport code and click "get weather".
4) Then go out and click "Analyze".

You can always click on the original data button and check for deltas that way.

You can also save the data pre-analysis and post-analysis. Just make sure they're named different things.

[5am]

My profile sets weather at my home area code. But most rides I do take me through many area codes and the wind and temps can and do vary greatly during my rides from that provided for my immediate home. More times than I can remember I've done rides with strong winds that are not reflected in the weather data it is checked against. In other words, I often return home glad to no longer be riding into a stiff wind only to see that the analysis shows a negative ground speed for the trip. Frustrating. If I monkey with the ground speed average (because I can naturally - the button is right there) I can get very large changes in my power figures. But I really don't understand this function well (I've read the manual), so I've just learned to leave the numbers alone and go with what the analysis shows despite my instincts to the contrary. I'd like to hear a lot more from people on how they check their own wind analysis. But I fear this is one of those areas where an aerodynamic engineers' hat may be necessary and I definitely lost that hat somewhere in a gusty breeze.

[leonsrocketcar]

I monkey with the ground speed average (because I can naturally - the button is right there) I can get very large changes in my power figures. But I really don't understand this function well (I've read the manual)

I hear ya, but with all the new bells and whistles with IB2, the manual is lacking in what the functionality of such neat (possible destructive) buttons. I was simply asking what all these things do in the analysis section. How they work, what is the purpose and why I would need to use it.

Most of the time weather underground has our local wind correct, but not Sunday or yesterday. Way off.


When the powers that be get time from future B&W development maybe they could answer the questions here and/or update the manual when they add the garmin Q&A. Garmin thread is hitting 600+ views. Bells and whistles from IB2 get super low numbers (does anybody use the functionality or are we paying for something we don't need or don't use cuz we don't understand?).

When is the first iBike Users conference/camp? Then we all can meet, ride, geek out on this stuff and learn alot of cool stuff to be more dangerous to ourselves!

[Velocomp]

We're thinking about July, in Montana. We'd have day rides, training with power lectures, iBike 2 lectures, maybe even a factory tour!

Any interest out there?

[aytchkay]

Hmmmm...riding in Montana AND learning about riding with power & iBike??? Sounds interesting.....I would be interested if it's not too expensive...
Let us know what you're thinking, John. I think there WOULD be interest in a 'camp' like that.

aytchkay
in chicago

[Site_Admin]

How about this - Anyone interested in may Jackson Hole, WY this summer? We'd go do the Beartooth Highway?

[leonsrocketcar]

I am split down the middle:
1. Riding outside of Houston is ok with me, anywhere not flat is great
2. I want to spend a day or 2 learning all the geekness of the iBike and troubleshooting issues .

So MN or WY works. So does Dallas and we can ride your hood and you can make us pancakes every morning

[Site_Admin]

Maybe pancakes at Denny's. I can't even boil water.

John is on the road this week - we'll have a chat upon his return and will figure out what to do for locations and logistics next week.

[5am]

How about folks keep this on the original topic and post interest on an ibike gathering on the other thread...Thanks.

[leonsrocketcar]

..... the original topic....

Which was requesting Travis, John, or Richard...or anybody to give a few paragraphs on the functionality of the wind offset under detail analysis advanced settings of IB2.

Let the mods move the threads on camps and pancakes to the other thread I created on such fun things

[Site_Admin]

use it every time. But the best way to figure out if it's necessary is to go ahead and analyze it, and then see just how 'off' everything is. Today, I had a 'tailwind' of just 0.3mph. So I corrected it, made sure the most local weather station was in the analysis, ran the advanced analysis, and the difference was around 3 watts. It was colder today, so I should have left the iBike out a little longer to adjust, and I probably hurried the wind offset.

[travispape]

..... the original topic....

Which was requesting Travis, John, or Richard...or anybody to give a few paragraphs on the functionality of the wind offset under detail analysis advanced settings of IB2.

Let the mods move the threads on camps and pancakes to the other thread I created on such fun things

If you can do a good wind offset calibration before you ride, then there is no reason to adjust the wind offset later. A good wind offset is to actually ride with your iBike for 3 - 4 miles or so (longer if the unit started at room temperature and you are riding in freezing temperatures). Stop and get the iBike unit out of the wind and do a wind offset. (Shielding the wind port with your hand or glove probably isn't going to work that well. Get off the bike and out of the wind.)

I know that it can be a lot of trouble to do that for every ride; however, let me point out that it is worth taking that trouble before your calibration ride (coastdowns and 4 mi out-and-back).

Now I don't usually end up doing the above wind offset cal, so I often end up using the wind offset analyze feature in my own rides. (I usually leave the iBike mounted on the bike in the garage or set it outside in the shade while I'm getting ready to leave. The problem with these methods is that a connected garage is not the same temperature as outside and when you sit the iBike outside, it is sitting on something with thermal mass that will influence its temperature. Riding temperature will usually be different.) However, keep in mind that if you do take the trouble to get a good wind offset, you don't have to worry about changing it later during the post-ride analysis.

That said, if the wind offset is off and I need to fix it, here's how I break down the repair process:

If the ride is a solo (ie, non-drafting) out-and-back ride, I set the average wind speed to zero. (By the way, the average ground wind speed in the wind analysis window is a distance-based average. This kind of average takes care of the fact that you spend more time on average riding slower against the wind than the faster wind-aided portion of the ride.)

If the wind conditions changed significantly during the duration of a solo out-and-back ride, I make the appropriate adjustment. For example, if the wind picked up for the return portion of the ride and it was a tail wind, I might enter a -0.2 or so for the average ground wind.

If the ride was a solo loop, I usually set the average wind speed to zero; however, you might need to adjust if part of the loop had high wind exposure while the other part of the loop was shielded.

If wind conditions are calm for a solo ride, I set the average wind speed to zero even if it was a one-way ride.

If the ride was one-way and wind was blowing, I use the airport data and the direction of the route to and the amount of wind exposure on the road to reduce the result. The roads here where I ride are carved through a sea of trees, so I greatly reduce the airport wind measurement for my estimate of the road speed. For example, if I do a one-way ride towards the East on a cold morning with a non-idea windoffset cal and the airport reports the wind was out of the NW at 10 mph, later when I post-process the ride I would assign a wind of -1.0 mph. (Negative because it is a tail wind; much smaller than the airport data because it was not in the same direction as my ride and because most of the ride was very shielded by the trees.)

Even if you ride in an area with lots of wind exposure, remember that airport wind readings are 10 m off the ground and are much higher than you would get on the road.

Drafting is another complication. If you did some of the ride in a paceline or peloton, then the best thing you can do is highlight a portion of the ride where you were in the clear wind and do your windoffset analysis for the whole ride just based on the highlighted portion of the ride. If you are riding a crit, but ride solo to warm up, base your wind speed correction based only on the solo part of the ride. You can typically expect a large virtual tailwind for rides where you benefit from a good draft. Drafting is more difficult to repair later, so if you know you are going to draft, you have extra incentive to go out and do a good windoffset before the ride. If you do go to the trouble, you will get a really good measurement of effectiveness of the draft based on the measured wind speed data.

Travis

[leonsrocketcar]

Travis,

Many thanks for the in-depth response. I understand what the functionality and how it can be used or misused to align oneself with the outdoor conditions.

I definitely put my iBIke outside (the garage) so it gets to outdoor temp while I get my bottles ready, dress, etc. Then I go into the garage to do my altitude/offset/tilt. There is just no way I can get a shielded calibration once I leave the house. It has been so windy here and shouldn't die down for awhile. I have tried the hand over port and it doesn't work to well as you point out.

Kevin

[pjboyle]

I have followed the above thread with interest, but still have the following questions...

1. On rides originating from my house, I do a pre-ride tilt check in the garage, then acclimatize the bike/iBike outside the garage while making final ride preps (water bottles, getting dressed, etc.). Then I bring it back inside the garage and do a wind offset. This seems to match the recommended procedure, but if the temperature of the unit is so critical, what about the fact that my ride is starting quite early in the day and by the time I return 3 hours later the temperature may be 20-25 degrees higher?

2. On post-ride analysis, the options button gives a series of choices on temperature. But on page 34 of the manual it states: "Note: If you've made rides with FW 1.15 and above, the temperature is stored in your ride file." I have FW 1.17, therefore I never do anything with the temps. during the analysis. Is this correct?

3. I often carry the bike on a rack for 10-15 minutes and originate the ride remote from my house. On these occasions I have been following the same procedures as 1. above, and doing the wind offset prior to putting the bike in the carrier. I generally remove the iBike from the bike mount during the transport to the remote location, and reinstall it when ready to ride. Would I be better off leaving the iBike mounted while in transit and use this time to further acclimatize the unit to ambient temp (and then do the wind offset at the ride start point)? My issue there is the lack of a shelter to take the bike into. Is it acceptable to do the wind offset out of the mount while holding it in the hand inside the truck?

4. Can someone explain why you can't simply seal off the wind port with your hand to do a wind offset if there is no shelter? I recall seeing either in the manual or in Rich Wharton's video that you can cup your hand around the front of the unit, but NOT TOUCH the wind port. Is the problem the temperature of your hand? Could you seal the unit with something like saran wrap that is at ambient temp (think condom) and do a wind offset this way? I have done two sets of 15+ CDs with accompanying 4mi, but since I ride a considerable distance to the location that I do these, I am wondering if my original wind offset should be repeated immediately prio to the CD set. The problem is the lack of any shelter at this location. So are these CDs suspect due to no wind offset out there? The CDs where conditions were the best yielded a CdA of 0.430 and a Crr of 0.0035. I did not expect a low CdA since I am old, chubby, and ride on the hoods.

5. I am also not really getting the whole thing with the weather station connection during the post ride analysis. Weather Underground does not find my local airport (BTR) or town (Baton Rouge). The manual doesn't seem to address this, so I am generally just sticking to the quick analysis.

Sorry if these questions are somewhat dense, but this wind offset seems like a critical factor for unit accuracy and I would like to get it right.

PJ (not a physicist) Boyle

[Site_Admin]

I have followed the above thread with interest, but still have the following questions...

1. On rides originating from my house, I do a pre-ride tilt check in the garage, then acclimatize the bike/iBike outside the garage while making final ride preps (water bottles, getting dressed, etc.). Then I bring it back inside the garage and do a wind offset. This seems to match the recommended procedure, but if the temperature of the unit is so critical, what about the fact that my ride is starting quite early in the day and by the time I return 3 hours later the temperature may be 20-25 degrees higher?

The iBike firmware works with that change in temp and subsequent changes in the barometer. This'll continue to be improved in future firmware updates.

2. On post-ride analysis, the options button gives a series of choices on temperature. But on page 34 of the manual it states: "Note: If you've made rides with FW 1.15 and above, the temperature is stored in your ride file." I have FW 1.17, therefore I never do anything with the temps. during the analysis. Is this correct?

It's not necessary - though I personally use the 'set weather' from my local "K" or "W" based weather station. It's user choice.

3. I often carry the bike on a rack for 10-15 minutes and originate the ride remote from my house. On these occasions I have been following the same procedures as 1. above, and doing the wind offset prior to putting the bike in the carrier. I generally remove the iBike from the bike mount during the transport to the remote location, and reinstall it when ready to ride. Would I be better off leaving the iBike mounted while in transit and use this time to further acclimatize the unit to ambient temp (and then do the wind offset at the ride start point)? My issue there is the lack of a shelter to take the bike into. Is it acceptable to do the wind offset out of the mount while holding it in the hand inside the truck?

You probably don't want to have anything strike the air pressure sensor above 50mph, which can happen when the bike is on a roof rack. However, it's definitely a great way to get the ibike acclimated to the environment. I always throw the ibike in the car with me when I'm ready to do a wind offset on a remote location. Still air is always better than windy conditions, hand cup or not, and the interior of a car is your best bet. So do proceed this way.

4. Can someone explain why you can't simply seal off the wind port with your hand to do a wind offset if there is no shelter? I recall seeing either in the manual or in Rich Wharton's video that you can cup your hand around the front of the unit, but NOT TOUCH the wind port. Is the problem the temperature of your hand? Could you seal the unit with something like saran wrap that is at ambient temp (think condom) and do a wind offset this way? I have done two sets of 15+ CDs with accompanying 4mi, but since I ride a considerable distance to the location that I do these, I am wondering if my original wind offset should be repeated immediately prio to the CD set. The problem is the lack of any shelter at this location. So are these CDs suspect due to no wind offset out there? The CDs where conditions were the best yielded a CdA of 0.430 and a Crr of 0.0035. I did not expect a low CdA since I am old, chubby, and ride on the hoods.

I'm no longer recommending that method, and we are probably going to reshoot the video this spring. The problems include vortices, vacuums, swirls, etc., and if you close off the air pressure port completely, you create false pressure, or the lack thereof. Do it in a car or a garage and you'll get the best data. Just do the wind offset in your car and you'll be fine.

5. I am also not really getting the whole thing with the weather station connection during the post ride analysis. Weather Underground does not find my local airport (BTR) or town (Baton Rouge). The manual doesn't seem to address this, so I am generally just sticking to the quick analysis.

It's a known bug. Just to go weather underground's website, then type in your zip code, and look for the K value for your closest weather station. I think yours is "KBTR"

Sorry if these questions are somewhat dense, but this wind offset seems like a critical factor for unit accuracy and I would like to get it right.

PJ (not a physicist) Boyle

No questions are dumb. We just need to keep educating.

[5am]

In detailed post-ride analysis, should I do the wind analysis before I do the tilt/power analysis? Or does it not matter?

Also, While I suppose it would be difficult to estimate how 'off' power figures might be per an individual ride if the wind offset feature is not as precisely calibrated as you note in your post above (i.e., doing a few miles out on the bike to acclimatize the iBike meter), care to make a guess? 2%? Less than 3%?

I'll just mention that two days ago I did a 40 miler in a heavy crosswind (17-25 mph with gusts to 33 mph/I was traveling primarily east to west then back and wind was mostly from the south). Wind analysis put my average ground speed at +0.4. If I reduce the figure to 0.0 like you mention above, I drop about 5 watts average from the entire ride. That also turns the ride from a 'tempo' ride at my current 60 minute FTP to an endurance ride, albeit at the high end of my endurance. Given that I didn't acclimatize the iBike meter very well before setting out on the ride (I did my usual 5 minute lap around the parking lot to make sure all human, mechanical, and electronic systems were a-ok before lift-off and then set the wind offset to zero as best I could while facing north against the wind) I'd have to assume that perhaps setting average ground speed to 0.0 after the ride is probably more prudent. (And there goes the 'tempo' ride. Sigh.)

[travispape]

In detailed post-ride analysis, should I do the wind analysis before I do the tilt/power analysis? Or does it not matter?

The order doesn't matter for the buttons. If necessary, the program will temporarily undo other tweaks that you have made to keep all the calculations "elastic".

Also, While I suppose it would be difficult to estimate how 'off' power figures might be per an individual ride if the wind offset feature is not as precisely calibrated as you note in your post above (i.e., doing a few miles out on the bike to acclimatize the iBike meter), care to make a guess? 2%? Less than 3%?

On occasion, I have seen the wind speed under-reported by 4 mph or more when riding with a compromised wind offset cal.

I'll just mention that two days ago I did a 40 miler in a heavy crosswind (17-25 mph with gusts to 33 mph/I was traveling primarily east to west then back and wind was mostly from the south). Wind analysis put my average ground speed at +0.4. If I reduce the figure to 0.0 like you mention above, I drop about 5 watts average from the entire ride. That also turns the ride from a 'tempo' ride at my current 60 minute FTP to an endurance ride, albeit at the high end of my endurance. Given that I didn't acclimatize the iBike meter very well before setting out on the ride (I did my usual 5 minute lap around the parking lot to make sure all human, mechanical, and electronic systems were a-ok before lift-off and then set the wind offset to zero as best I could while facing north against the wind) I'd have to assume that perhaps setting average ground speed to 0.0 after the ride is probably more prudent. (And there goes the 'tempo' ride. Sigh.)

Depends on whether the wind direction chanced during the course of the ride, how much the iBike changed temperature, and how much wind got around your body during the wind offset cal. Further, keep in mind that even if the averge wind should have been 0 mph, if you rode with a significant crosswind, your effective CdA would have been higher than your nominal CdA. Raising CdA would increase the power. And before you ask, no, I don't know exactly how much to raise the CdA to compensate for the crosswind. The effect of cross wind is a function of the rider and position.