Wind offset question

[jim_s]

I did a 34mi non-drafting ride today and didn't have time to do a wind offset before heading out (was running late). Temp in my office is 68 degrees. Temp outside was about 52-54 degrees over the course of the ride. Watts seemed a little high at times based on perceived effort (though I was working hard to stay warm - I under-dressed in my rush to get outside, in addition to skipping the wind offset calibration... Did a out-and-back-ish loop (rode out one side of a ridge, then up over & back the other side). 1st side had a minor shifting wind (iBike reported 1.6mph headwind ave), 2nd side had a noticeable headwind (iBike reported 7.4mph headwind ave). 1st side was rolling hills, 2nd side was an 11mi, 1% ave downhill section, followed by a 2mi 6% climb. Wind analysis window shows a 0.0 offset w/ a 1.8mph ave ground wind. Ave speed for the ride was 17.9mph.

So, should I expect my watts numbers to be off by any significant amount due to the skipped offset? In the future, if I'm in a rush and can't do an offset once the iBike has adjusted to the outside temp, am I better off at least doing an offset in the office before heading out? (so that I at least have some known state?)

Appreciate any assistance, and apologize for asking what I know is about the umpteen-thousandth wind offset question, but the limited search capability of the forum made it difficult to find potential prior answers.

Incidentally, this was on a Gen III unit, which from what I can tell thus far, completely ROCKS!!

Jim

[Velocomp]

The temperature stability of the wind sensor is much better in the Gen III so it should not be a major crisis if you forget to do a wind offset. On my Gen III I often do not perform a wind offset; I put the iBike on my bike, push the center button to pair, and ride.

[jim_s]

So does 'no major crisis' translate to watts likely being off by 1-2w or 10-20w, or some generally-estimable perceived head/tail wind or such? (This isn't critical stuff, it'd just be good to have some correlation between temp diffs and offset effects so I can take that into account when riding and looking at numbers.)

Thanks Again!

[coachboyd]

If you are doing a loop and get an average wind speed of 1.8 mph, that seems very reasonable. Remember, there is only about 120 degrees of wind direction that actually helps us on the bike. If you have a crosswind, that is not aiding you to go faster.

Many of my rides I have forgotten to check the wind offset at the start of the ride. The comparison between my Quarq and the iBike has been great though, and if I notice it to be off, it's usually by less than 5 watts. If you can do a wind offset at the start, that usually helps bring up the last bit of accuracy. But most times, if it does happen to be off, it's by less than 3.0 in the wind offset screen. That 3.0 is a much more sensitive number than mph, so it's not like your wind speed would be off by 3.0, more like .6 to 1.0.

[jim_s]

Thanks for the info Boyd - looks like I'll have to do more of my training on cold days, under-dressed then, as I seem to work a little bit harder than normal...

[pjboyle]

Related question on "how-to" do wind offset....

I often drive to the start of ride point with the bike on a rack. At home prior to the ride I will typically put the iAero outside while I prepare bottles, inflate tires, etc., then just before getting in the car, I do a wind offset and put the iAero in a pocket for the drive over (10 or 15 minutes). Once at the start point I put the iAero back on the mount but I am usually on the bike and riding in just a couple of minutes, so I don't do another wind offset as the unit is not back to ambient temp yet. Since the unit will reaclimatize to virtually the same temp where I did the windoffset prior to the drive, I am assuming the original wind offset is still "good" despite the intervening heating/cooling cycle. Is this a safe assumption?

PJBoyle

[Velocomp]

The main thing to know is that the Gen III is MUCH less sensitive to temperature changes. Your procedure is fine...

[rruff]

Since the unit will reaclimatize to virtually the same temp where I did the windoffset prior to the drive, I am assuming the original wind offset is still "good" despite the intervening heating/cooling cycle. Is this a safe assumption?

Probably. I still haven't upgraded my Gen2 but I often do something similar... only over the course of a day. If I do an offset one day at 50 degrees, and the temperature the next day is about the same, then I just leave it with the old offset. Seems to work fine. I hear the Gen3s are calibrated at the factories now so they are much less influenced by temperature. It seems that there is a voltage influence though, so if it is really cold out the voltage might drop enough from one day to the next to effect the offset.

[jim_s]

rruff, you haven't gone to the Gen III yet?? I'm shocked! You gotta do it - I can tell you first-hand, its definitely a worthwhile upgrade (minus the whole custom interval thing, but they're working on that...

[rruff]

rruff, you haven't gone to the Gen III yet?? I'm shocked!

Me too... sorta. I was going to jump on it right away, but then I wondered if I should get mount with external battery... then I thought about getting a wireless setup... then I thought about getting an old wireless on ebay, and upgrading that... and then my wife expressed interest in getting one, or maybe using my old one, etc.

Basically the Gen2 I have works fine. I don't have issues with tilt. The most annoying thing is the temperature effect on the wind offset. I haven't even had battery issues yet with the wired mount. It has been in the high 40s or warmer every day that I've bothered going out on the road bike, and the battery seems to last 20hrs or so.

[jim_s]

Yeah, I hear you - my Gen II was working pretty darned well, too, and it was a bit of a question as to whether or not I'd benefit from the new unit. My main thing was that I live in a fairly hilly area, and I regularly had my numbers being noticeably off on the latter part of mid-to-long rides due to increasing tilt/elevation differences (post-ride analysis could be off by as much as 10-20 watts for the latter parts of the ride.) I think my max post-ride difference on about a dozen rides now has been 2-3 watts, and the wind offset sensitivity seems to be much reduced. Those items have made it worthwhile to me.

Downsides are I could swear its a bit more vibration-sensitive than my Gen II, and the minor changes to the mounting details, or perhaps the plastic change, make it downright difficult to get off the mount. It seems to be made of a bit-more-brittle plastic now, too, which has me a little worried about durability long-term.

Overall though, its been a good upgrade!

You have a wife who covets your iBike? Now *that* is cool!!

[FelicianoVASA]

Hello, everybady

I have a GenI and after training in the rain the wind seems to be wild. I have reset and at flat and descending the watts go very high. How can I resolve the problem?

Anyone can help me?

Best Regards

Feliciano Vasa from Portugal

[pjboyle]

Feliciano,
I have had the iBike ingest rain water several times (each time leads to very high wattage numbers). After the ride, I have dried the unit by opening the battery compartment and removing the battery, and then leaving the unit open (battery side up) under a light bulb (I use a low wattage desk lamp). I generally leave it this way overnight. The bulb warms it to the point the case is warm to the touch but not overly hot. With this procedure my unit recovered each time and was normal for the next ride.

One area I overlooked previously after wet rides was the mount. I had a wireless mount fail due to corrosion from water intrusion, and I had not previously checked inside the mount after wet rides. Now I keep a light grease layer on the mount battery closure. After a ride in the rain I check it, and if wet inside I and remove the battery and leave it open until the next ride.
PJBoyle

[FelicianoVASA]

Hello,

Tank you. I have done as you told, but the high numbers at descending are there.

To the velocomp and people with the same problem:

-A new coast down can help?

[FelicianoVASA]

Nobody as reply, but I have search some opinions and found out that a new calibration can help fixing the problem.

Thats what I did just a few minutes ago. Four coast downs and a four mile ride (two miles turn back). It seems that work well. After ending the coast downs I notice a improvement in the readings. Not the amazing, thousand plus power readings anymore. Back home I analyze the ride and voilá, the numbers are normal again.

I post this so I can share ith others my experience. Thank you again pjboy by the tip.

[lorduintah]

One thing that happened to me a couple of times until I realized what was going on - the first part of my ride had ridiculous data - high speed, tilt changes, all sorts of things. This only happened after I put my Corima wheels on (Aero in front, tri-spoke in back). I take my bike to a park on a car carrier. The back wheel spins freely as the aerodynamics of the tri-spoke take effect. What was happening was the 1.5 mile ride was getting recorded and I was not doing a trip reset before starting out at the park. My other wheels don't act like that, so I was not correlating the effects together.

Now I wait until I get to the park to put the iBike on the wireless mount, run through the battery and wind checks - take a quick look at the tilt and off I go. No more early crazy data.

Tom