How does Gen III deals with strong winds?

[xptxc]

Hi !

My first post here

I`m very interested in Gen III Ibike pro or aero, and read almost all the forum`s topics, but there`s a question where I have still some doubts:

How does IBike deals with strong winds?

I ride in a flat area near a river or the ocean, usualy winds don´t go bellow 10 miles/h, its very easy to get 15 miles/h during a all week and some days in a month (like today) you get 24 miles or a bit less.

A typical praticing ride will be going East for 2 hours against strong front winds and the returning West with strong tail winds, or go 50 milles south with strong tail winds and returning with strong front winds - we also do circular rides where wind vary a lot but not that often.

Thanks in advance for your replys !

[racerfern]

Welcome aboard!

I live on the coast and experience fairly strong winds. The iBike handles them very very well. It easily picks up tailwind and headwind. See the attached picture with the following notes. Mileage notation is approximate.
Mile 0-6 - ride up the coast in a light headwind occasionally catching a draft from other riders. This was to meet the group.
Mile 6-13 - ride back down the coast but now in the pack for a nice leisurely warm up and conversation. This was a tailwind AND in the group.
Mile 13-31 - regular riding, some climbing, not so much in the group but still getting a helping hand from the wind most of the time.
Mile 31-38 - ride back up the coast in a strong headwind. You can clearly see where I take the pull about seven times.
Mile 38-44 - ride back home with a buddy. No drafting, just side by side enjoying the tailwind.

I hope this gives you an idea of how well the iBike handles wind.

[xptxc]

Fernando,

Thanks a lot!

Just one more question:
In that situation was power measurement reading consistent?

[racerfern]

I guess I should have grabbed the power info also. But to answer your question the power readings were consistent with the wind levels and my efforts in those winds. So riding hard into a headwind yielded considerably more power than riding along in a tailwind.

Also riding hard in the draft while going headwind required more power output because it still took quite a bit more effort to hold a given speed because the wind although diminished some was still tough. If you look closely at the graph in the 31-38 mile area of the graph you see "tailwind" when drafting but without the consistency of a true tailwind ride. That's me moving around behind the rider in front of you looking for that sweet spot.

[iodaniell]

Fernando,

How come it looks like your wheel speed drops to zero in places? I don't think I've seen that before.

[rruff]

How does IBike deals with strong winds?

Pretty darn well if you get it calibrated properly. In Gen3 models you won't have to worry about temperture changes screwing up your offset, which is helpful. I've heard some (old) claims that sidewinds can be underreported, but I haven't noticed much of a problem there myself.

[racerfern]

Fernando,

How come it looks like your wheel speed drops to zero in places? I don't think I've seen that before.

Traffic lights and stop signs buddy! The Sunday group is good about stopping at lights. Groups have even gotten tickets.

[R Mc]

The weak point of the G2, wrt wind in my experience, involves strong cross-winds.

Mine has performed really well in groups, great in head and tail winds, and pretty good in low angle cross-winds--but, predictably, it under-reports in cross-winds approaching 90 degrees (e.g riding east with a 15+ south wind). My non-engineer explanation involves the brake-hoods and my hands blocking some of the wind exposure.

Anyone else experience this . . . and will it be better in G3?

[rruff]

...will it be better in G3?

AFAIK G3 will have no effect on your hand position...

[coachboyd]

It's not actually due to your hand position. Your actual cda changes in a heavy crosswind. Because you are cutting through the wind to your side, it's not frontal area being measured.

I am fortunate to live in the Carolinas, where we have great crosswind races in the early spring (and excellent opportunities to spend an hour or so single file in the gutter). I have found that it takes a good 20+ mph of crosswinds to have effect on the wattage readings. Of course, if you are changing direction at all, this will change. But yes, wind coming from 90 degrees sideways will have an impact on accuracy. Fortunately, this realistically happens not very often.

[R Mc]

That sounds about right--I notice it much more on the high-wind days . . .

Of course, out here in West Texas (I ride past the world's largest wind farm regularly), 20mph days are fairly common. But even then, stretches of complete side-wind are relatively infrequent.

As for hand position . . . well, honestly, I ride in the drops mostly, so really it's the brake hoods blocking the sensor most of the time. I suppose I could ride fixie and take care of that problem

[racerfern]

The weak point of the G2, wrt wind in my experience, involves strong cross-winds.

Mine has performed really well in groups, great in head and tail winds, and pretty good in low angle cross-winds--but, predictably, it under-reports in cross-winds approaching 90 degrees (e.g riding east with a 15+ south wind). My non-engineer explanation involves the brake-hoods and my hands blocking some of the wind exposure.

Anyone else experience this . . . and will it be better in G3?

True crosswinds can be a challenge. If they are strong at 15+ then the iBike under reports. 15+mph winds are huge winds. It's not often you see that kind of wind speed at ground level. BTW my non-engineer explantion is more of a venturi effect at the mouth of the iBike but there are smarter people than me out there that might have a better explanation.

However, I don't consider this an issue since I've only seen this at exactly 90 degrees and because the amount of time spent in this situation is such a small percentage of a ride. Inevitably you turn in one direction or the other and of course the wind is ever changing. Even the slightest change from EXACT crosswind will make wind effect show up properly on the iBike.

Just like you feel tailwind if the wind basically crosswind but ever so slightly behind you and you feel headwind if the wind is crosswind but ever so slightly facing you the iBike reports correctly in these situations. I consider crosswinds inconsequential when it comes to the big picture.

[rruff]

It's not actually due to your hand position. Your actual cda changes in a heavy crosswind. Because you are cutting through the wind to your side, it's not frontal area being measured.

Just thinkin out loud... I'm not sure I get that. What we are talking about (I think), is say you have a 90 degree 15 mph wind and you are going 15 mph. The resultant wind angle is 45 degrees and the resultant wind speed is 15/sin 45= 21.2mph. Since aero force is proportional to V^2, take 21.2^2 * sin 45 and take the square root of the result, and then subtract your forward speed of 15... and you end up with an *effective* headwind of 2.8 mph. This is *without* your CdA changing at all, and it's why most of us experience that crosswinds slow us down.

I think the issue with the iBike is that the static pressure reading is effected by the interference of our body, bike, hands etc, in the airstream... and it will vary somewhat in different wind conditions. For instance if you calibrate your wind scaling for zero wind, then with strong crosswinds the pressure around the unit will be different. One way to visualize it is to imagine a "bow wave" created by you as you pass through the air. No way to fix it that I know of except moving the iBike farther away from your body (not practical). One way to check it is to ride back and forth on a road where you have strong crosswinds and see if the windspeed averages to zero. I do that sometimes to check the wind scaling anyway, and I haven't found moderate crosswinds to be a significant issue.

[iodaniell]

Fernando,

How come it looks like your wheel speed drops to zero in places? I don't think I've seen that before.

Traffic lights and stop signs buddy! The Sunday group is good about stopping at lights. Groups have even gotten tickets.

:thumb up:

[coachboyd]

Just thinkin out loud... I'm not sure I get that. What we are talking about (I think), is say you have a 90 degree 15 mph wind and you are going 15 mph. The resultant wind angle is 45 degrees and the resultant wind speed is 15/sin 45= 21.2mph. Since aero force is proportional to V^2, take 21.2^2 * sin 45 and take the square root of the result, and then subtract your forward speed of 15... and you end up with an *effective* headwind of 2.8 mph. This is *without* your CdA changing at all, and it's why most of us experience that crosswinds slow us down.

I think the issue with the iBike is that the static pressure reading is effected by the interference of our body, bike, hands etc, in the airstream... and it will vary somewhat in different wind conditions. For instance if you calibrate your wind scaling for zero wind, then with strong crosswinds the pressure around the unit will be different. One way to visualize it is to imagine a "bow wave" created by you as you pass through the air. No way to fix it that I know of except moving the iBike farther away from your body (not practical). One way to check it is to ride back and forth on a road where you have strong crosswinds and see if the windspeed averages to zero. I do that sometimes to check the wind scaling anyway, and I haven't found moderate crosswinds to be a significant issue.

I think we're on the same page. Because your hands and brake hoods are pretty much at a 90 degree angle from the wind port of the ibike, you would have to be going 0 mph for the brake hoods to be in the way. Say you have a 30 mph wind, as you speed up the angle of the wake of your hands changes, but it's going to be almost impossible to make the wake travel straight across 20-22 cm (half the bar width) while you are moving forward to interfere with the wind port of the iBike.

I can't remember the source, but I seem to remember reading that we only have 60 degrees of wind that will help us go faster. That means the other 300 degrees of wind angle will slow us down (given the exact same wattage and road conditions).