The Why's and How's of Wind Offset

[dusand]

Aaah OK now I see what you mean. I did buy the remote wind sensor but didn't bother to install it yet, and given the recent appearance of spring weather here in London, I'll probably wait until next autumn. By the way, are they any help in wet weather?

Dusan

[lorduintah]

I don't have one, but they probably help a little. Would depend on where you mount it relative to the standard port. It would certainly put the water away from the iBike - until the tube filled up, anyway.

Tom

[dusand]

I'll mount it in autumn and see what it does...

[Velocomp]

Actually, the RWS can be a big help if you ride a lot in the rain.

What happens is this: if it's raining and water gets in to the RWS tube, then the water is trapped in the tube and does not enter the wind port. Even with water in the tube you'll still get excellent wind speed readings.

[thomas_cho]

Please pardon my newbie question ... but this wind offset thing ... do I cup my hand over the air port, make sure I am in still wind, and then press the button to do the wind offset? Is there a need for the reading to be 0 before clicking?

Also I should do this BEFORE doing a calibration ride?

I have also recently changed the position of my ipro unit (from the right side of my bars to the left side) do I need to do a calibration ride to rework the wind scaling factor?

[Velocomp]

Low wind speeds are like mere puffs of breeze--think of a candle flame flickering as you walk by it.

The iBike wind sensor is very sensitive and, like any sensor, has a level of electronic "noise". The wind calibration removes the electronic noise from the signal, so that smaller wind speeds can be measured.

When entering the Cal Wind screen in setup, if the number is not zero (or within a few tenths of it) then you need to do a Cal Wind. Your procedure for the Cal Wind is correct. After the button is clicked the reading will drift towards zero and the iBike will exit setup automatically after a few seconds.

It is very important to do a Cal Wind prior to a Cal Ride--so much so that the iBike checks to be sure the Cal Wind was done no more than 30 minutes prior to the start of a Cal Ride.

Finally, I would most definitely do a new calibration ride after moving the iBike around on the handlebars. The air that flows by the iBike is very dependent on the position of the iBike on the handlebars, and it may be different on the left side as opposed to the right side.

[gerrard]

I've read this thread a few times over but still don't quite understand it. Is doing wind offsets (Cal Wind option in setup?) the same as Auto Wind that happens when I first turn on the ibike?

I live in a windy city (Wellington NZ). It's nearly always windy, and very rarely calm. I try to find a calm-ish location for my calibration ride but this is difficult to do. What is the impact of doing a calibration ride in windy or gusty conditions?

Also, when I do "Analyse Wind" in the ibike software I get a difference between the wind speed and wheel speed. It shows me Wind Offset number between -0.5 and 3.1 and Avg Groundwind numbers between -1.2 and 3.1. What does this mean and should I do anything about it?

Cheers
Gerrard

[racerfern]

I've read this thread a few times over but still don't quite understand it. Is doing wind offsets (Cal Wind option in setup?) the same as Auto Wind that happens when I first turn on the ibike?

Yes.

I live in a windy city (Wellington NZ). It's nearly always windy, and very rarely calm. I try to find a calm-ish location for my calibration ride but this is difficult to do. What is the impact of doing a calibration ride in windy or gusty conditions?

With minimal wind it's easier to pickup the slight variances in wind than it is with the wind blowing at 10mph for example. In addition when you have more wind you tend to have higher wind gusts that can skew things even more. Ideally you're looking for a 1-2mph wind which is really more like the slightest of breezes. Look at historical data for the time of day that has the least wind (5am?) and shoot for that. Also think about making a day out of riding somewhere else that might have less windy conditions. Do your cal ride then go for a ride in that area (just a suggestion).

Also, when I do "Analyse Wind" in the ibike software I get a difference between the wind speed and wheel speed. It shows me Wind Offset number between -0.5 and 3.1 and Avg Groundwind numbers between -1.2 and 3.1. What does this mean and should I do anything about it?

It depends how much of a headwind/tailwind difference there was, so there's not much to be done. Note that wind offset is one thing and wind speed is another. If you have your wind scaling set up via a good cal ride and you do a proper wind offset at the start of the ride and maybe again during the ride if conditions change, you shouldn't have to click on Analyze Wind. Simply click Analyze Route and it all gets taken care of. IF you have a specific problem with wind then you can make adjustments in Analyze Wind.

Hope this helps.

[gerrard]

That's really useful. Thanks

[NorBike]

When I do wind cals, first I find a flat place that looks pretty wind free. Then I gently place a small plastic transparent plastic bag over the unit and bracket, making sure it’s closed but not tight around the unit or totally closed, so I don’t make a “new atmosphere” around the unit. This way gives me good wind cals.

What I have found is that the wind sensor has to be tilt depended (Newton), so I think that it’s not a good idea to unmount the unit and place it inside your jersey, or go and find a wind free place (indoor). It has to be on the bike, preferably at 0.0% tilt. You can try to hold the unit at +/- 40%, blow gently into the wind port and getting no response, but holding it at 0.0% and it responds immediately.

It would be nice to get some feedback from Velocomp about plastic bag around the unit when doing wind cals, the link between wind sensor and tilt, and consequences if doing a wind cal uphill at +10%?

[Velocomp]

When I do wind cals, first I find a flat place that looks pretty wind free. Then I gently place a small plastic transparent plastic bag over the unit and bracket, making sure it’s closed but not tight around the unit or totally closed, so I don’t make a “new atmosphere” around the unit. This way gives me good wind cals.

What I have found is that the wind sensor has to be tilt depended (Newton), so I think that it’s not a good idea to unmount the unit and place it inside your jersey, or go and find a wind free place (indoor). It has to be on the bike, preferably at 0.0% tilt. You can try to hold the unit at +/- 40%, blow gently into the wind port and getting no response, but holding it at 0.0% and it responds immediately.

It would be nice to get some feedback from Velocomp about plastic bag around the unit when doing wind cals, the link between wind sensor and tilt, and consequences if doing a wind cal uphill at +10%?

The wind sensor works at all angles, but we intentionally stop displaying the wind speed when the tilt is above 25%. There is no issue at +/-10%. The plastic bag works very well to establish calm wind conditions.

[Russ]

Norbike said:
"What I have found is that the wind sensor has to be tilt depended (Newton), so I think that it’s not a good idea to unmount the unit "

I have also observed, not exactly a dependency but rather an oddly intermittent sensitivity, may be the way to best describe it. I have noticed two things about this.

First I have seen it have a different zero point between truly level and mounted at, I forget but perhaps 20 degrees - nose up, this is intermittent. Also I have seen a slow time to settle to where zero can be achieved when tilted.

I do find that if I zero the wind in the mounted on bike and tilted case it usually does not work well on my ride. Once I made this distinction and started doing my wind cal with it level I no longer need to redo the cal, when I check it at level it goes to zero - seemingly always if protected from the wind.

I have also found that, in my car port, placing the iBike nose pointed inward in a plastic hand shovel with a blade shaped as a cylinder that is cut away from back down to the front end then it is quite easy to turn and protect it from the wind for a wind cal.

So now, as John says, I can usually just mount the unit acquire the sensors and ride.

Regards,
Russ

[GeorgeHotopan]

I was browsing the other night through the forum topics and I came accross this very interesting topic.

I have read and digested so far the first page of the topic.
I saw that the topic was initiated late in 2008, when other units were available as well as FW versions. In my case with the Newton+ model and the FW 5 is there a need to do a Wind Offset (wind cal)? What about the position of the Ibike on the front mount, and by this I especially mean the tilting angle respect to the horizontal: should I aim for a particular angle range (eg: 0-10 degress) to get best readings possible? Or this does not matter and once the Cal Ride is done, Newton will automatically compensate for this internally. Haven't done the Cal Ride yet (hopefully if the weather does not change much I will be able to do the call ride this afternoon, and post the file for confirmation).

Any opinions or advices are mostly welcomed!

I am keen on learning all the features of this amazing device, so every once in a while, when I get some spare time I browse through the forum looking for valuable data.

Best regards,

George.

[Velocomp]

This is a old topic, and covers older-generation units.

The Newton 5 is MUCH more stable than previous generation units. You can check the Cal Wind if you wish, but it's no longer obligatory. Angle is not critical, and once the Cal Ride is completed the Newton will figure out automatically any corrections needed due to angle.