High wattage on flats at high sp/low effort

[schroed15]

In the past week or so, I've noticed that my Gen III iAero has begun showing much higher than expected watts when I'm traveling at speeds of more than, say, 20mph on relatively flat (+/-1%) roads. The disconnect between the watts on screen and my perceived exertion is probably on the order of 20-40 watts consistently, but greater (by as much as 150-200 watts) when my speed is particularly high such as after I come off a fast descent. I noticed the difference because I'm used to seeing watts in a certain range for endurance effort rides on familiar routes.

I have been using the same profile, position and equipment all year--no changes there. My iAero has performed awesome up to this point and this issue has me stumped. Anyone have any ideas about what the problem might be?

[Velocomp]

Please post a ride file showing the problem

[Morocco Mole]

I would do another CAL ride and check your wind scaling.

[GWPOS]

I have noticed the same thing on rides also, but I think mine is more around the 23mph mark. Anything under that my numbers are right on. I also have power number issues after doing long climbs (10 or more minutes) and then turning around and going downhill. For the first 4-5 min after doing so while going back downhill my numbers are 40 watts or so higher than they should be. Everyone keeps telling me that my aero is off, but these high numbers stop after that first 4-5 min after turning around and going back downhill. I have the reverse problem after going downhill for longer than 10 min or so where my numbers are really low when I start climbing again which goes on for ......you guessed it, 4-5 min then it corrects itself. When I then look at my downloads the IBike software corrects it so that I can not see the watts or something to that effect. I coasted once for the first 5 minutes after climbing for awhile and had a constant 50 watts until the 4-5 min mark and then my watts went to zero. When I looked at my ride file later I seen no watts at all in the IBike software.

I really like my IBike but some of this stuff really baffles me, especially when no one from IBike can tell me why my unit does these things. But I guess the good out weighs the bad and for the most part am happy with my unit.

[lorduintah]

Sounds like an artifact of the auto-tilt correction. I wonder if it is not kicking in on the ride up, then ride down - even if it is supposed to be only the first 5 minutes of your riding. Maybe it is a lurking bug?


Tom

[GWPOS]

I think you are right, but everytime I do a post here on the forums I get answers like my aero is off or in the most recent time rally nothing at all helpfull. I make sure to keep my body in the exact position everything to see what causes this, but finally came to the conclusion despite what they said, that it has something to do with the auto tilt adjustment. Maybe they will see our post and have an answer to these little problems this time???

[Velocomp]

Please post a ride file.

[schroed15]

Sorry for the delay in getting a file posted...here is one from a short ride I just finished. The issue can be seen between minutes 19-22 of the ride file. I was cruising down a smooth, mellow grade on a road I ride frequently. On this stretch, at the effort I was putting out, I would normally see zone 1 watts--something less than say 130w. However, the iAero was reporting watts in excess of 200 for most of this stretch. Like I said in my first post, this is unusual and has only been happening for the past couple weeks, but it has occurred consistently on all my rides during that span.

Thanks in advance for any help!

iBike_08_11_2010_1542_9_Miles.csv

(497 KiB) Downloaded 342 times

[GWPOS]

Ok here is a little example of my problem. I am in a rest week so I did an easy ride today with a long climb. After the climb I turned around abd heade back downhill. I was backpedaling and it only happened for the first 2 min today (instead of 4-5min) but i was getting watts constantly around 80-100 for that whole 2 min. After that my watts went to zero like they should have been.Then after the download I see some watts after turning around but not like I was seeing on my IBike during the ride. I did not have time to do the rest of my ride to show what i mentioned it does after turning around and going back uphill. Which is if I turn around right after going downhill for 10 min or so and then start climbing again it reports my watts to low (maybe by 40-50 watts) again this only happens for about 5 min., but when doing max effort or FTP intervals it makes hard to impossible to keep my watts according to what the unit is saying. Again after that 5 min everything goes back to normal and I can do my intervals the way they are supposed to be done.

iBike_08_12_2010_1730_14_Miles.csv

(1020.08 KiB) Downloaded 321 times

[schroed15]

Here's another file from a ride that I did this morning. This is one of my more frequent training routes. One note I should add with regard to both files I've posted, is that the higher-than-normal wattage that I see while on the bike is largely not reflected in the files. The iBike software appears to make corrections for a good deal of the high wattage when the files are downloaded.

For example, during this ride my power as displayed during the ride was consistently above 200w, though the watts reflected in the ride file are more in line with what I would have expected to see during my ride, given the effort. I made a couple mental notes during the ride so that I could compare with the file post-ride: 1) watts on the road between minutes 29-34 were between 200-260w, but in the ride file, the average for this section was more like 165w (more reasonable); 2) my average power near the end of my ride at 1:45 was 190w on the road, but is 156w in the file (again, file seems more reasonable based on effort).

Again, this discrepancy between power on the road, especially on flat to slightly downhill sections, and power in the ride file wasn't substantial until recently. The iBike software has always adjusted the road watts a bit, but the adjustments were pretty small.

Hope this is helpful...thanks again for any feedback!

iBike_08_13_2010_0923_35_Miles.csv

(1.6 MiB) Downloaded 314 times

[rruff]

Ok here is a little example of my problem. I am in a rest week so I did an easy ride today with a long climb. After the climb I turned around abd heade back downhill. I was backpedaling and it only happened for the first 2 min today (instead of 4-5min) but i was getting watts constantly around 80-100 for that whole 2 min. After that my watts went to zero like they should have been.

I see power values fluctuate +-200W if I'm on long downhill (~35mph), and the wind is gusty... but I don't know if that is your issue. Yours could be an artifact of auto-tilt correction, and 80-100W is not a lot if you are at higher speeds.

[GWPOS]

Ruff... I know we have had this discussion before but I never really got an answer other than my aero was off. I know my aero was good because as stated this problem only took place for 4-5 min then it went away. Anyways I just heard back from someone and found out it is a product of the auto tilt having to catch up. At least now I know there is nothing wrong with my unit. As for shroed15 this may be your issue to only a different circumstance. I get the same wattages you mentioned once in awhile on ride on the flats or slight downhills at high speeds.

[schroed15]

GWPOS...The % grades I see on the road look reasonable, so I'm inclined to believe my tilt is good. On one of the long false-flat sections where I see the issue, I did a short out and back keeping an eye on the grade. Looked pretty consistent on the negative going down and the positive coming back. The auto-tilt catch up issue is interesting, though. Wonder why it only does that when going from uphill to downhill?

What's got me puzzled is that my iBike only just started doing this, and I'm not sure what to attribute it to. Absent changes that would affect drag, such as a different position or equipment, I don't know if a profile can go "bad." Regardless, I tried setting up a new profile, too, but same issue. Since the software seems to correct a lot of the high wattage after downloading the ride file, it seems like that somewhat validates that my profile is ok, but can't understand why the on-the-road watts are out of whack.