ibike and Cross Winds

[ejl773]

In South Florida, we may not have hills or very cold weather, but if you have been on A1A before, you know that we have tons of cross winds. I find when the cross winds are out the power data is all over the place. My power readings seem to be much lower today than usual. During my three hour ride this morning, I did a 30 min TT during the beginning part of the ride. My average mph was 25.7 with an average power of 256. Typically my FTP is around 307 and mph around 25.5. Also, on the second half of the ride, the cross winds really picked up. It was a heavy cross wind as well as a headwind. My power readings dropped down in the mid 100s and an even got as low as 110. I was struggling to maintain 18 to 20 mph because the winds were very tough. This does not make any sense to me. I continue to have issues with my ibike and this is just another one of them.

Lastly, my ibike froze up about 3 minutes into my TT and I had to start all over again. This is the first time my unit has froze with the new firmware. It was freezing on me every other ride with the last version. My firmware is all up to date and I have the newest one, 4.04.

Is anyone else having these issues?

Eric

[arkiejon]

I have not had a single problem with my unit other then short battery life on cold rides.

I have had my wireless IPro for a little over two months and live and ride in the hills of Northwest Arkansas (Most people don't know it, but we do have paved roads here ). We may not get cross winds like you do but we do get them.

I like the IBike so much and have had little to no trouble with it that I ordered a second unit yesterday for my other bike.

[rruff]

If it is a TT bike then where is it mounted? A better way to diagnose these things is to do specific testing for the wind scaling in a variety of conditions. Did you check your wind offset as well?

[racerfern]

In South Florida,...Also, on the second half of the ride, the cross winds really picked up. It was a heavy cross wind as well as a headwind. My power readings dropped down in the mid 100s and an even got as low as 110. I was struggling to maintain 18 to 20 mph because the winds were very tough. This does not make any sense to me. ...
Is anyone else having these issues?

Eric

Please post the ride file(s), we'll have a look.

[ejl773]

It is mounted under the base bar on the right side. iBike themselves mounted it there. I live about 30 minutes from ibike and John helped me with the set up. I ride with a podium quest aero bottle between my aero bars. Can the aero bottle block some of the wind out of the left and affect how the wind is hits the RWS?

Ride file attached.

[ejl773]

Sorry, here is the file.

[Velocomp]

n South Florida, we may not have hills or very cold weather, but if you have been on A1A before, you know that we have tons of cross winds. I find when the cross winds are out the power data is all over the place. My power readings seem to be much lower today than usual. During my three hour ride this morning, I did a 30 min TT during the beginning part of the ride. My average mph was 25.7 with an average power of 256. Typically my FTP is around 307 and mph around 25.5. Also, on the second half of the ride, the cross winds really picked up. It was a heavy cross wind as well as a headwind. My power readings dropped down in the mid 100s and an even got as low as 110. I was struggling to maintain 18 to 20 mph because the winds were very tough. This does not make any sense to me.

This is a good ride file to discuss.

You did a 60 mile ride, turning around at mile 30.

I think your Cal Wind was correct, because your tail wind turns into a head wind at the turnaround point and your average wind for the entire ride is 0.4 mph (you say that winds picked up in the 2nd half of the ride). On an out-and-back ride the average wind should be around zero; in your case it is a bit higher than zero because of the increase in wind during your return leg.

The first 30 miles of your ride shows a measured tail wind of 2.0 mph. This is where you did your 30 minute TT. Your average bike speed was 25.1 mph and your average wind speed was 23.2. You say that your normal FTP is 307W (based on ride data you submitted to me previously in October, I estimated your FTP to be 297W) with a bike speed of 25.5. Note, however, that when riding outdoors bike speed is dependent in part on wind speed! You had a tail wind of 2 mph, giving you an extra push during your TT. The tail wind made it easier for you to achieve your speed of 25.1 mph so your NP was only 261W.

Interestingly, if your wind speed is adjusted in the Analyze Wind feature to hold an average ground wind speed of zero, then your NP for the TT rises to 297W.

So, my suspicion is that you're managing your TT pace according to your bike speed. If you managed your pace according to your FTP then your bike speed would have been higher for this ride, due to the tail wind.

In the second half of your ride, things look fine. Your ride follows my "20-20" rule of thumb: riding on the hoods, on the flats and without headwinds, 20mph bike speed requires 200W. For example, look between miles 36 and 41. (Your headwind is compensated for by your TT ride position).

Towards the end of your ride your watts do drop to around and NP of 126W, but your HR is dropping significantly too, indicating that you are, indeed, working less hard (average bike speed is 14.7 mph)! Also, you've got lots of places where your cadence is zero; this will drop average watts. See for example miles 50-52. A bit later you pick up the pace and watts rise accordingly (miles 52.5 to 54); bike speed is 17.8 and NP is 157. Having done hundreds of miles at this pace on A1A (my weight loss program) this speed/watts relationship is in line with my personal experience.

At the very end of your ride there are many places where cadence is zero. Average bike speed is 13.9 mph but you've got a strong headwind of 4 mph. However, with all the zero cadence and slow bike speed, NP is 107W. Note that HR drops way down at the end of the ride, corroborating the lower level of wattage effort.

In summary, it appears that your iBike faithfully recorded your exercise effort for this ride and that cross winds would seem to not be causing low readings.

[ejl773]

I did not manage my TT with mph. I was trying to hammer it. When I do a TT, I do not focus on the numbers while racing. I do TTs to establish HR and Power zones. I could not get the Power up where it normally is. The reason for the slowdown towards the end of the ride was becuase I blew up. The power data was much too low. Riding in zone 2 felt like riding in zone 4.

[ejl773]

One more thing to my last repsonse. The ride file can tell you a lot; however, it cannot tell you the acutal amount of effort a rider is using during the ride. Only the rider can tell you that. All I can say is that the power data did not match the amount of effort I used. This caused me to blow up on this ride and other rides in the past. When I ride with cadence and HR, I never low up. I have blown up on more then one occassion when riding with the power data generated by the ibike.

[racerfern]

Sometimes I change the smoothing to a radical number. It definitely shows trends. See the attached picture. Everything dropped proportionately once you hit the headwind. It makes sense that from 01:50:00 to the finish you were either pretty much baked or cooling down. Only you know which one, but the constant drop in HR suggests something strange is going on with you. I don't see the cross winds as an issue here BTW. Just my 2 cents.

[rruff]

Thanks for posting the graphs Fernando... makes it much easier to see.

*If* the wind is consistent during a out-back ride and there is a strong crosswind component, then the correct average wind speed is >zero. In other words a straight crosswind in both directions will slow you down compared to no wind... unless you have some fancy aero components that significantly reduce drag at high yaw. The iBike can have some difficulties with rendering this accurately, especially if the wind was coming across some obstructions (arms and bottle) before getting to the wind sensor.

You contradict yourself regarding your pacing method. Did you pace by feel, or did you pace by the iBike reading? I always pace TTs by feel, and only use the power data to inform me after the fact. Sometimes it is obviously off... usually when there is a lot of wind... but it tends to average out also on an out and back. It will fluctuate a lot too in these conditions (like +-100W), and NP is useless. It is the nature of the beast... or mine at least. There is no way I'd ever use it for pacing when it was windy. I suspect that you really didn't have an effective tailwind on the way out, the iBike reading was a little low... and you were using it for pacing... and went too hard.

[Velocomp]

Attached is an image of an October 3 TT ride for this cyclist.

There was a slight head wind for the October 3 TT; about 1.0 mph. My personal experience is that I work harder in a headwind than in a tailwind, (the Dec 5 ride had a 1.7 mph tailwind) and perhaps Boyd and others can comment why headwinds/tailwinds might affect relative efforts.

The average speed for the October 3 TT was 25.4 mph, into a headwind. Comparing the October 3 result to the December 5 result, the October 3 bike speed is higher than the December 5 result of 25.2 mph, despite the headwind of the October 3 ride. Also, average HR for the October 3 TT was 173; on the December 5 TT the average HR was 164.

Based on the data, the October 3 TT was a higher level of effort. Note that, using the October 3 data, and taking 95% of the average power of 314W yields an FTP of 299W, lower than the reported value of 307W.

If I understand the thread correctly, the rider reports that the iBike was not used to "manage" TT power pacing for the December 5 ride. Therefore, that there was a bonk near the end of this ride would seem to have no relationship to ANY number reported by the iBike for this ride, power or otherwise.

Prior to the December 5 ride I set up the RWS personally on this bike and it is a neat and "clean" setup. There are no obstructions from water bottles or arms.

Though this thread began with a question about the iBike, it also reveals a nice sidelight: iBike ride files include data about weather conditions of each ride. This is something no other bike computer does, and weather information can help cyclists understand why perceived efforts may, in reality, be different factually from day to day.

[ejl773]

The effort used in both TTs was about the same. The reason for the HR differences was weather and health. I do not recall the temperature and humidity back in October; however, it was much hotter and humid back in October than normally. It is very likely the temps were in the 80s during the October TT. It was in the 60s during my TT on 12/5. I always do my HR zones at least twice per year, once in the late fall/winter and then again spring/summer. This way I can train based on the correct HR zones. Heat and humidity have a major impact to HRs. On top of it, I was just getting over a cold and fever during the October TT. This would explain the higher HR.

Fernando - My pacing for TT varies, if I am doing a 30 minute TT (10 min hard warm-up followed by 20 min TT for data gathering), I basically do not pace at all. I hammer it for 20 minutes as hard as I can. The purpose of this is to calculate my HR and Power zones based on the data the ibike generates from the last 20 minutes of the TT. If I am racing in a TT, I pace by feel. However, when I am racing a half ironman, I should be pacing by power.

Ruff stated I always pace TTs by feel, and only use the power data to inform me after the fact. Sometimes it is obviously off... usually when there is a lot of wind... but it tends to average out also on an out and back. It will fluctuate a lot too in these conditions (like +-100W), and NP is useless. It is the nature of the beast... or mine at least.

I think something was confirmed to me in this thread. I have always felt the ibike was not for me and possibly not for triathletes. I am a triathlete who races all distances, sprints, olympics, half and soon to be full Ironman races. When racing the longer distances races, I should be pacing off power. My bike training schedule posted by my triathlon coach requires me to pace by power. I am no pro, but the pro triathletes who race with power meters pace by power. I have had a number of issues with the power data, especially when it is windy. The power data is not helpful to me after the fact, well, it can be, but it is more important to me when racing.

I am currently training for Ironman St. George. I have not cycled out there but my research tells me the bike course can be windy at certain points. If I am suppose to be pacing based on power and the power data can be off when windy, the ibike just will not work for me. I believe the ibike is a powerful piece of equipment, but I feel it should not be used as a stand alone device. It seems it would work better when combines with an SRM, Powertap or soon to be speedplay power meter pedal system.

Eric

[Velocomp]

The data keeps getting more and more curious...

I looked up the weather for each of these dates.

At 7PM on October 3 (the time of the TT), winds were out of the due East at about 5 mph. This is a true "cross wind", as A1A (the road we all ride) goes north and south. So, it is not surprising that there was a small oppositional wind component on the October 3 ride.

At 8AM on December 5, winds were out of the South at 10 mph. In the physics sense of wind as a vector force, a south wind would not be a cross wind nearly as much as a tail wind. Indeed, if the TT was ridden north there would have had a tail wind, as indicated by the iBike. Buildings along A1A will swirl the wind, possibly creating cross wind components...

Temperature on October 3 at 7PM was 82F; on December 5 at 9AM it was 75F. I do not know the dependence of HR on temperature; maybe someone else can help with this.

Even with all the discussion of this thread there is still the fact that average bike speed on October 3, with a headwind, was greater than average bike speed on December 5, with a tail wind. It is difficult to describe a scenario where the power effort for these two rides would be equal.

[bex]

I am still getting to know my (and my wifes) units and cannot offer too much insight into this thread.
I would like to make a comment that looks obvious to me though.
Everything mentioned above suggests to me that you have possibly overtrained and are currently experiencing this, the lower HR but higher perceived effort.
Has your coach (or are you self coached and I misunderstood) analysed the data (can he/she? and by that I mean are they capable)
What was your resting heart rate compared to the October ride?
What is your resting HR now?
Is your training plan being modified to account for the peaks and troughs of health and wellness?
I believe your comment regarding the usefulness of the Ibike Data for triathletes is wrong, my wife is a triathlete and finds the data useful, helped her do a positive run split in IM Canada
But, given that you would buy another, what would it be and upon who's recommendation, your coach?
Just my 2 c's FWIW, trying to be helpful rather than critical.

Cheers and best of luck

Bex

[coachboyd]

The effort used in both TTs was about the same. The reason for the HR differences was weather and health. I do not recall the temperature and humidity back in October; however, it was much hotter and humid back in October than normally. It is very likely the temps were in the 80s during the October TT. It was in the 60s during my TT on 12/5. I always do my HR zones at least twice per year, once in the late fall/winter and then again spring/summer. This way I can train based on the correct HR zones. Heat and humidity have a major impact to HRs. On top of it, I was just getting over a cold and fever during the October TT. This would explain the higher HR.

Fernando - My pacing for TT varies, if I am doing a 30 minute TT (10 min hard warm-up followed by 20 min TT for data gathering), I basically do not pace at all. I hammer it for 20 minutes as hard as I can. The purpose of this is to calculate my HR and Power zones based on the data the ibike generates from the last 20 minutes of the TT. If I am racing in a TT, I pace by feel. However, when I am racing a half ironman, I should be pacing by power.

Eric

This can explain a lot, especially the health part. To hammer a 20 minute time trial with optimal results, you need optimal preparation and to be feeling on your game. If your health wasn't good and you were getting over a cold, you're not going to be able to put out the power that you could in prime condition.

Around here we have monthly 10 mile time trials on Lowes Motor Speedway. It's a great way to test monthly as it's right around a 20 minute effort. Even though it's "only" 20 minutes, I can tell you that some of my most spectacular blow ups of the year have come about 13 minutes into the 20 minute event. These usually happen when my power for the first three to five minutes is higher than I can normally maintain. I will post one of these files, if you take a look into it you will see that I really didn't have it this night. I started off at what I normally could maintain for twenty minutes (pacing by power is important even for 4K pursuit riders on the track), but I soon started cracking. At the beginning I was maintaining 340 watts, by the end I was struggling to hold 270.

What was the reason for this?
I just wasn't feeling good. Earlier in the year I have ride files where I was maintaining more in my warmup. This was towards the end of a long year and motivation wasn't there for me anymore. I was looking forward to being off the bike, and going all out for twenty minutes when you're not 100% psyched up for it is a very hard thing to do.

So, trying to hold what I know it's possible for me to hold during a time trial, I blew up and pretty bad. If I was really listening to my body, I would have held back a little bit more at the start (maybe 315 watts versus 340), and I might have been able to maintain an overall higher average wattage.

This brings me to the next point. The iBike measures ALL the variables that oppose you, many times per second. It's impossible for your legs to be as well calibrated as the iBike. In your file I saw cadence slightly dropping at times, speed dropping (maybe traffic intersections), and other variable that can very briefly lower the watts without you even realizing it (especially if you were pacing off of feel). Your body has a natural tendency to want to back off the pedals, we overcome that and push through and that's what keeps us moving forward. At higher speeds, especially in swirling wind, you may have slightly backed off for a couple seconds without even realizing it. Even in my time trial file that I posted, there are a few times when my watts dip below 180, and this was an all out race.

In the iBike data part of the file, you'll see a couple times where for a second the power does a small dip. This is where I move back in the saddle from sitting on the tip and the bike will shift under me. The iBike sees this as a slight slowing down and lowers the power for a second. It's THAT accurate to where it can tell when the bike is being moved backward underneath you for a moment.

Basically, there are a lot of factors into measuring power and the iBike can measure them all, many many times per second. It is VERY possible to blow up in a 20 minute time trial, especially if you weren't feeling good or if you started off too hard. By doing more intervals based on pacing by power you can really learn to listen to your body and it will also help to increase your strength and improve your fitness.

[racerfern]

Fernando - My pacing for TT varies, if I am doing a 30 minute TT (10 min hard warm-up followed by 20 min TT for data gathering), I basically do not pace at all. I hammer it for 20 minutes as hard as I can. The purpose of this is to calculate my HR and Power zones based on the data the ibike generates from the last 20 minutes of the TT. If I am racing in a TT, I pace by feel. However, when I am racing a half ironman, I should be pacing by power.

Eric, I have to respectfully disagree with either you or your coach, and please understand I am not a professional at either cycling or coaching. I've been training by power for almost three years and understand enough to be dangerous.

My concerns in your statement are:
1) In the process of doing a hard warmup then a 20TT you're warming up too hard and using up energy that should be saved for the 20m TT.
2) If you go all out for the 20m TT from the start you will be cooked rather quickly. Your cadence begins to drop putting more and more pressure on your muscular system. This is clearly visible in the chart I posted. Your FTP may not be what your think your FTP is. The 20m TT test is a good barometer of FTP but if you have other issues, there is nothing like doing a 60m all out test. There's your real FTP.
3) Why bother setting HR zones. You're either training by the power numbers or you're not. Have you had blood work done to determine your lactate threshold? IIRC your power zones should be set around your FTP and lactate threshold but after that you're using power numbers, that's it. Regular testing will reveal if your LT shifts.

Anyways, like others here I writing to make positive suggestions not to criticize you.

[ejl773]

I would like to clarify that I was feeling FINE and 100% during the December 5th TT. I was not feeling good during the October TT. My power and HR was much higher during the TT when I was NOT feeling 100%, this does not make any sense. Also, I am a stronger rider now than I was in October. I am a competitive age group triathlete taking making many 1st to 5th place podium finishes this past year. I never had an issue with racing or blowing up until I switched to the ibike.

Also, I want to clarify one thing about the 12/5 TT. I do not use the first 10 minutes for data. I slightly hold back during the first 10 minutes. The data I use is from the last 20 minutes. I am not at home right now, but I think the avg mph during the last 20 minutes was 25.7 mph which is faster than the October TT but watts were much lower. I was hammering it and could not get the watts up if my life depending on it.

I have had good days and bad days with the ibike. It is just too inconsistent for me. It may work for you guys but for some reason it does not work all the time for me. I have heard many similar issues from other local triathletes that use the ibike.

The recommendation to get another power meter came from Craig Alexander, World Ironman Champion, and Richard Nixon, age group winner at Clearwater 70.3 World Championships. Rich is not my coach but I did consider him. I had the opportunity to meet and speak with Craig Alexander at a race I did a few months back. I think these two athletes are qualified to offer advice.

Lastly, I am well rested and this is not the issue.

[Velocomp]

I appreciate everyone's comments on this thread.

The bottom line is that we have data which is in conflict with perceptions. We can't change the data and we can't change perceptions, so it's probably best to move on to another topic.

[rruff]

Everything mentioned above suggests to me that you have possibly overtrained and are currently experiencing this, the lower HR but higher perceived effort.

My heart rate at say ~120 min max power will vary +-15bpm at least depending on what I've done in previous days. It is useless for pacing at this level, though it gets a bit tighter at shorter and more intense levels.

ejl773... I would encourage you to *learn* to pace by feel. IME watching numbers does not put me in the correct "zone" for racing. It's much better if I concentrate on body sensations. I don't do triathlons though... so for me the bike ride is the whole race, and it is in the 25-55 min range.

[ejl773]

Ruff - When doing a half and full ironmans one should be pacing in power zones 2, 3 and sometimes 4. It is very important to have the data work during the race. It does me no good to have the data and analyze it after the race. The data after the fact is helpful when analyzing my race, but like I said, I need the data to be accurate when racing. One of the reasons power zones were created is for pacing.

[pjboyle]

Personally I have used the iAero to successfully pace my effort in several century rides. The unit performed well in all conditions of crosswinds, paceline, etc. I had no reason to doubt it. In Wichita Falls, TX this year I was able to use power output as well as IF during the ride to pace to my first sub-6 hr. ride for the 102 miles over the circuit course. It was windy there and the circuit produced wind from every direction.

Here's a marketing idea for Velocomp...
Produce a model in a special red case. Call it a "Professional Racing Model" or "Lab Model" (sorry Racermate!), and charge $2000 for it. Nothing else needs to be different. The data will be universally believed.

PJBoyle

[arkiejon]

Produce a model in a special red case. Call it a "Professional Racing Model" or "Lab Model" (sorry Racermate!), and charge $2000 for it. Nothing else needs to be different. The data will be universally believed.

I market and do retail sales, you may or may not know how close to true your statement is.

[coachboyd]

Of course that model will be engineered in Germany as well.

[bex]

Nah, just have the box made in Germany and stamp "made in Germany" on the box

Bex

[R Mc]

I have some apparently conflicting observations to report about iAero performance in cross-winds on a tt-bike set-up.

1. I have seen my iAero under-report in a complete side-wind. It was much worse if the cross-wind is perpendicular (90 or 240 degrees) or slightly behind. This under-reporting was more pronounced on my time trial bike than on my road bike. (And this under-reporting was even more pronounced in previous FW versions: there's a section of a race from early March where the iAero recorded 85w when my heart rate recorded 183 (and my AT is 174)--that section occurred as we raced eastward along a stretch of road exposed to a 30+ mph North wind. Those discrepancies no longer occur).

2. I calibrated the time trial bike using a power tap. Whilst riding to the road on which I do the calibration rides, I encountered several cross-wind sections (I suppose I could dig through my files and attach these, but won't unless asked). During those cross-wind sections, the iAero reported really high cdas (as high as .430) relative to the .24xs I normally see). I assumed that that almost doubling of the cda accounted for the discrepancy between the watts reported by the iAero and my rpe.

3. Except . . . that I subsequently removed the topeak-like extender (with the iAero mounted underneath the aero-extensions) because I was unhappy with the wind-scaling numbers. I mounted an RWS with the iAero mounted atop the stem (on top of a head-set spacer, as demonstrated by Boyd a while back). I recalibrated with the power tap and obtained a WS value right around 1.

4. After that, the performance of the iAero in all wind conditions has improved. Although I'm pleased about that, I'm a little perplexed as to how it could be if the cda actually varies with respect to total side-exposure.

[Velocomp]

There's no doubt but that the RWS will do a much better job with TT bikes, and will also improve wind scaling factors.

Also, we made a change earlier in 2009 in the FW to improve cross wind performance. I believe your ride file from March was prior to that change.

I don't understand issue 2 at all; please send a ride file.

[R Mc]

Here's the two ride files.

Sept 21 is time trial bike with topeak underneath bars;
The sections in question occur between miles 5 and 6 and 11.5 to 13 in this file.

October 16 is with RWS.
The sections--around mile 8 and mile 22 (note: much less apparent under-reporting at mile 8 as compared to Sept. 21, and at mile 22 apparent OVER-reporting)

[turbomentor]

Coming in to this thread late but...

I may not be as competitive a triathlete as the OP, but I've successfully used my iBike in races from sprint to Ironman since I first started using it a year ago. In regards to his TT effort, I have little to offer except to echo what another person posted and that is a 20 min TT is one of the least reliable methods for obtaining an FTP number. But I'm not going to criticize another person's training techniques because they are as varied as there are coaches.