Until I do an accurate calibration...

[nreimche]

On average, what should my average watts for a 3 mile, 8 minute, time trial be if, I am sitting upright/hands on hoods, w/ deep rim American Classic wheels, wind breaker type jacket, w/ sleeves rolled up, on an Kestral Rt700 frame, w/ aquarack, tights, 2 water bottles, etc. The rest of the options are minor, but I figured the sleeves rolled up (because it was comfortable), sitting upright, w/ a jacket instead of a, tight, jersey, and the aquarack (mounted on the seatpost behind the seat) are major drag contributers. If need be, forget the rims and water bottles, unless there is a comprehensive website for such SPECIFICS.

I've read about analyticcycling.com are there any others? I appreciate any feedback, thanks!

[Velocomp]

If you have an iSport or iPro, use the Est CdA function to give you a good approximation of your aero drag, and use 0.006 for a good estimate of Crr (rolling resistance). Then, do the Cal Ride only, then get out and ride!

After you do your coast downs you can use the newer profile with your older ride.

[MultiRider]

I put my new Gen III on my bike, entered the basics such as wheel size, height, weight, took all the defaults, and it seemed very accurate to me -- I was blown away by how reasonable the results seemed based on approx 1 year with the original iBike (which compared very favorably to a PT). In addition, I did a couple simple tests -- pedaling without putting any pressure on the pedals with the expectation that the watts would be 0, then pedaling lightly to see if the watts started showing up at light pressure. Both tests worked very well, though at higher speeds (>25mph) it started taking substantial pressure to register watts. Hopefully a calibration ride will correct that.

I did about a 55 mile ride and my iBike performed flawlessly the whole time.

I should mention that I really like the "Good Tilt" message -- I used to double and triple check my tilt and then worry about it some more later. Getting "Good Tilt" and knowing that the iBike is constantly re-evaluating Tilt gave me great confidence throughout the ride.

I'm VERY happy with my Gen III !!

[nreimche]

Where do I find the estimated aero drag function? Also is .006 a guess for standard wheels only? Remember I have American classic 420's which are around 2 inches deep. Thanks so far for the feedback.

[nreimche]

Where do I find the estimated aero drag function? Also is .006 a guess for standard wheels only? Remember I have American classic 420's which are around 2 inches deep. Thanks so far for the feedback.

[Velocomp]

You'll find the "Est CdA" and "Est Crr" screens in the setup menus of an iSport or iPro. They are not available in the iAero (ya gotta do the work in the iAero!)

[coachboyd]

Yes, I would recommend using .006 for an estimated crr.
As for estimated cda, if you are wearing a jacket your cda will be higher than if you were riding in summer clothes, so add about 5 pounds to your current weight and it should adjust for the jacket.

Of course, if you do the calibration ride, your riding tilt and wind scaling are stored. If you do a coastdown at the beginning of your ride (making sure that your tilt and wind offset are good) that will give you new aero and friction numbers. Couple that with the stored riding tilt and wind scaling and you now have cda and crr numbers and accurate results.

I have been testing that method here all week as the weather was colder and I was dressing for it. So far, the results have been really good when I look compared to my DFPM.

[ChrisS]

As for estimated cda, if you are wearing a jacket your cda will be higher than if you were riding in summer clothes, so add about 5 pounds to your current weight and it should adjust for the jacket.

As the jacket will give a higher cda, why not increase the cda. Increasing weight does not have any effect on cda and has minimal effect on measured power on the flat. Weight has most effect when going up hill when cda has least effect.

Adding 5 pounds to the weight as a workaround to compensate for a low cda will just lead to poor results. Why not do te job properly and change the cda.

[coachboyd]

Because there is not place to put your own cda (although that could be a feature). As it stands right now it's an estimated cda. A user will enter their weight, height, and position on the bars. It's not meant to offer the highest level of accuracy. So, when you add 5 pounds to the weight, the formula will change the cda to a higher number and you'll have more accurate results with the jacket. (Note: changing the weight in the estimated cda screen does NOT change the weight used for computing power for going up hill. It's only used to estimate the cda, that is why I offered that solution).

Of course, just doing some coastdowns will give you the most accurate results, but we wanted to give people an easy to use set up if they didn't want to use the coast down method.

[Silkhope]

I have the GenIII iAero so I can not enter height,weight, and position. Will be doing coast downs as soon as time and conditions allow but in the meantime I'm curious. Can someone with an GenIII iPro calculate est. Cda for me?

Height 72 Inches
Weight 165; with bike and winter clothes 190lbs
Position on the hoods

Thanks!
Tom

[Velocomp]

Tom:

Your estimated CdA on the hoods is 0.36 with summer clothing.

Your iBike has a default CdA of 0.4 loaded into it so it is probably quite close to your winter gear number.

I would just ride with the default values in the iBike. Once you do your coast downs and Cal Ride you can re-interpret your ride files with the corrected profile.

[ChrisS]

Because there is not place to put your own cda (although that could be a feature). As it stands right now it's an estimated cda. A user will enter their weight, height, and position on the bars. It's not meant to offer the highest level of accuracy. So, when you add 5 pounds to the weight, the formula will change the cda to a higher number and you'll have more accurate results with the jacket. (Note: changing the weight in the estimated cda screen does NOT change the weight used for computing power for going up hill. It's only used to estimate the cda, that is why I offered that solution).

Your right. I didn't understand that the change would be done on the ibike and not in software. I assumed that the profile would have been edited in software and then uploaded to the ibike.

Chris

[rruff]

Where do I find the estimated aero drag function? Also is .006 a guess for standard wheels only? Remember I have American classic 420's which are around 2 inches deep. Thanks so far for the feedback.

The .006 Crr is mostly for the tires. If you are running particularly good tires with latex tubes it will be less than this... but some tires with butyl tubes will be significantly higher.

AC 420s are 34mm (1.34") deep. Compared to very shallow rims with lots of round spokes this will reduce your CdA ~.01... not enough to worry about.

[nreimche]

Do you mean .001 Rruff? Is there a website, anybody, that would have a list of wheels (I have several different types) w/ the crr listed? Thanks Rruff.

[rruff]

Do you mean .001 Rruff? Is there a website, anybody, that would have a list of wheels (I have several different types) w/ the crr listed? Thanks Rruff.

CdA is aero drag coefficient. So it would be like a drop from .40 m^2 to .39 m^2. Crr is rolling resistance and the units are equivalent slope... .006 is like climbing a 0.6% grade. Rolling resistance is *not* a property of the wheel, but of the tires and tubes.

[lorduintah]

Crr is also a function of the road surface - which can have a significant effect.

Crr does have a small component of the wheel (there are bearings!)


Tom Anderson

[nreimche]

So wheels are a factor cda, right?

[lorduintah]

Why not - they do have a cross-section exposed to the path of movement and influencing air flow.. Why else Aeros or Discs? It is not just for the angular momentum.

I would not be surprised that these are detectable with an iAero set p.

Tom

[nreimche]

Could it be that wheels affect/effect both: Cda; and crr?

[coachboyd]

Yes, the depth of the wheels, shape of the spokes, how many spokes, and shape of the rim all contribute to the overall cda.

The tubes, tires, and bearings will effect the crr.

This link will show you how much certain wheels will save you in cda versus other wheels.
http://accel95.mettre-put-idata.over-bl ... nglish.jpg

[nreimche]

New question(s?), same ride: How come my average wind speed for the 3 mile tt's are positive in both directions? Is this same wind, because the bike is moving forward, actual wind, or a little of both? Specifically, I am referring to the left hand side or the ride info straight above the quick/details tabs.

Furthermore, at Kreuzotter.de, I put in the avg wind speed, mileage (per tt), avg slope, bike speed, whether or not I was riding on a road bike, drops, etc. However, my wattage at Kreuzotter.de was astronomical! I even calculated the ride in segments. I think either, THAT WEBSITE is off or my WIND PORT on my IBIKE is broken. For the record my avg watts for one of the tt's, as of kreuzotter.de, was 794. My avg watts for the ibike w/ the suggested/estimated CDA and CRR values, is only 297 or so. I would like to know if my ibike is funked'ified (bad)!?
I, also, want to have accurate numbers to put in Kreuzotter.de, so if wind is wrong in the ibike, and that was not the actual wind, but, speed-related wind resistance, or broken Ibike, I want to know. Here is the ride, if someone needs to see it.

This is 2 files of the same ride. One is the original file and the other is an analyzed/tweaked file!

Edit- You should be able to see the 2 tt's. After each one I turned around to go the opposite way, where the wind is above 15 mph in both directions. I did the tt's on almost, exactly, the same stretch of road.

[coachboyd]

It looks to me like you are blocking the wind port somehow in your TT position. This might also be the reason why your cda is reported as .600 (although it looks like it was originally .516). When the wind port is blocked in the TT position you will notice you can get fairly accurate speed readings at slow speeds, but when you start pushing the pace a bit, your hand (or whatever blocks the wind port) will start effecting it and you will get very low wind speeds compared to wheel speed.

Do you have a picture of your iBike and how it's positioned on your TT bike?

Also, this is kind of weird. I don't see a serial number in your ride. If you connect it to your computer can you get your serial and firmware numbers?

[nreimche]

I wasn't in the time trial position. As stated above I was on the hoods w/ winter gear and even sleeves rolled up. It does sound weird, but in the TRAINING RIGHT-time trial video, I saw the explanation of the CTS field test, The guy was not in a time trial position! So I was mainly doing the test to get a baseline of POWER to work w/ for the videos.
The sleeves were rolled up, not because I think they are cool, aerodynamic, or anything, but because it was hotter on the ride, but I wanted to get the power results over with.

Believe me I wanted the tt's over with sooner, because I was at maximum, but also I had no place to put the jacket, since I was several miles away from home and promised my wife I would be back by a certain time! Sorry, 'bout the run on sentence.

[nreimche]

By the way Coachboyd, I have the Ibike mounted underneath the stem w/ a barextender TYPE thing. My cables are out of the way, behind the ibike. I do not have a picture of the setup, no.

Again, by the way everybody, at the top of the thread I originally asked for a general idea of my wattage, because I had not had good conditions for decent coast downs. The profile in the attached files (a couple posts from the end) had an older profile, In the analyzed file, I did some coast downs and a 2 mile ride, w/ the same clothing w/ sleeves rolled up, as the tt's.

So, for an average rider, hand's on hoods, slight crosswind(up to 20 and down to 10 mph), slight grade(.8% or so?), w/ aero wheels (I'm not going to be exact for generalization purposes, but if you want American Classics 420s, non bladed spokes), Profile design aquarack (again, don't worry about this fact for generalization purposes), w/ winter clothes... what would be the wattage if I did 3 mile tt's in, about 8:20 (mins:secs)? Thanks.

[racerfern]

Obviously, taking a guess for some of the data, using http://www.saris.com/wattscalculator.aspx , I punched in the following data:

weight 160#
bike wt 20#
height 72"
distance 3 miles
elevation gain 136ft. (quick estimation from your csv file)
time to complete 8 minutes

The results are:
Power required to overcome gravitational resistance: 69 watts.
Power required to overcome rolling resistance: 40 watts.
Power required to overcome aerodynamic resistance: 189 watts.
Total power required: 298 watts.

Watts per Kg: 4.11
Watts per Kg with bike: 3.65

This assumes no wind and I have no idea how much you or your bike weigh. But that won't affect general calculations like this all that much.
Of all the calculators I've seen, this one seems to keep things simple enough to deal with and seems to give numbers that make sense. At least to me. YMMV

[nreimche]

Thanks racerfern. Now, not to get entirely away from what I want to know or what others may want to know, but how can I interpret analyticcycling.com? I put in some numbers and it seems like the watts are total waats, instead of the amount of watts that are actually going into the pedals. I've read that we as bodies are very inefficient machines. W/ that said only about 20% of the energy we us goes into the pedals. For instance, to generate 300 watts our bodys actually have to generate 1500 watts or so. Efficiency gets away from the discussion at hand, but how do I get a number I am familiar w/ (as mostly a lay person) from analyticcycling.com? Furthermore, even the default values showed thousands of watts, for a typical ride.

[coachboyd]

As far as efficiency, that is for the measurement of Kilojoules vs. Calories. One Calorie is equal to 4.1 Kilojoules, but our bodies are only 25% efficient while cycling, so it becomes one Calorie equaling 1.1 Kilojoules. Your iBike will show you both Kilojoules and Calories needed to consume to equal the Kilojoules on the display.

If you are beginning into the wattage world, analytic cycling can be a very complex site to try and understand. A much simpler site to use is located here http://bikecalculator.com/wattsUS.html. This can give you an approximation of what your iBike measures but remember, the measurement devices inside the iBike are very sensative and can detect VERY slight wind or slope changes and acceleration/deceleration. These very small measurements can often not be picked up by somebody plugging numbers into a calculator, so the online results can vary slightly from real world applications.