ride analysis done by software?

[ScottChapman]

So doing an epic ride yesterday. I had what I think was good data on the unit itself (showed 297 avg watts). But when I loaded it into the software it scaled everything down (resulting in 181).

Why the big difference? I am posting the before and after files if anyone cares to shed any light.

[racerfern]

The answer my friend is blowing in the wind. You show almost a 13mph headwind for the entire ride. Is that what it really was?

Assuming this was not an out/back ride then your average power was 195w. The problem is that the analysis tries to make it an out/back and tries to come up with zero wind in the process. But the question still goes back to "Was it really that windy?"

[ScottChapman]

Nope, not an out and back ride.

These were files from a friend (alo an iBiker) who did the same TT ride mentioned in the other email.

The route was an "n" shaped three leg route.

[racerfern]

Scott, the issue is wind related for both files and how the analyzer sees the ride. When doing analysis on a ride like this, try unchecking all the boxes and inputing your beginning and ending elevation.

I also have to question your setup as far as wind. I don't know if you're using a RWS but it may be that although the wind offset is zeroed for the ride, the wind scaling is quite high. For your friend with the Giant it is over 2 and for you in the other set of files it is over 3. If these are TTs are you using a TT bike and where is the unit located. Something doesn't make sense. Maybe a picture of setups.

[ScottChapman]

RWS?

Both bikes are standard road bikes. Mine the unit is mounted on the handlebars, and my friends is mounted on the stem.

So, here's the thing about my wind scaling. My original Gen-III iAero had a wind scaling of 1.242. The bottom part of the case broke, and I sent it in for repairs. When I got it back my power was way off so I tried to create a new profile. I would get a valid profile about 50% of the time but wind scaling would always be around 4-5. So, John sent me a replacement unit. Same thing. So I sent my original unit to John to look at, and he got WSF of 2.8 for a stem mount. I haven't been getting convinsing numbers reliably since.

Here is my set up (although I have since moved the unit to the other side, and nosed it up slightly per recommendations. But with no effect):

IMG_20100830_153344.jpg (246.15 KiB) Viewed 6132 times

[racerfern]

I can't help you with unit issues. However, your friends unit on the stem should not have a wind scaling of 2.x (I don't have iB4 at work so I can't look at the profiles). I would think his wind scaling should be in the .6 to 1.4 range.

On your bike, with the unit that close to the stem you might have 2.x but I'd be surprised if it went to 3.x which is what your profile shows.

Assuming you don't have unit issues, I would re-do a cal ride in as calm conditions as possible.

RWS is remote wind sensor, time trialers use it on their bikes because the body gets in the way of good wind readings. On road bikes it can be helpful but it's certainly not necessary.

[ScottChapman]

I have done approx. 15 cal rides since this problem started. Most of which have been dead calm days. My results have been pretty consistent. the WSF of 3.x is the lowest I have seen; more commonly I get in the 4.x range.

I don't think I have a unit issue (since I get the same results with two different units).

[racerfern]

Then it seems you've got it. It just seemed high and there were obviously wind scaling issues in the rides you posted so it made sense to look at that first. As long as you're comfortable with your calride then you need to look at what made the original un-processed wind data be so high. It's so high that it's almost unrideable.

[ScottChapman]

I am comfortable with what I did for the cal ride (although I think roughly 50% of them failed because the WSF was too high). I am just not particularly comfortable with the results as you can see.