cda questions.

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GWPOS
Posts: 178
Joined: Mon Aug 24, 2009 2:47 pm
Location: Yucaipa, Ca

cda questions.

Post by GWPOS »

I have been using my new Newton for a couple of days or so. I did my cal rides, tried coast downs which gave me super high cda numbers. Something like .570 and so forth. Changed my profile back to default settings for my height and weight etc. This puts my cda at .350. Now when I did a ride I went into the coast screen and had really high "-" numbers. Over 100 watts. I then changed my cda to .360 which helped some but again changed it to .379. I am still getting a "-37"- "-67" wattage. I am kind of worried that if I keep changing it higher that I will not have a good profile. I have my crr set .60 which is about right for the road I was on. My perceived efforts are noticeably higher on descents as is my heart rate. So my question is should I adjust my cda a little more in order to get the number closer to fluctuating around zero or do I really risk messing up my profile? My profile is set to on the hoods. Body weight 163 and height is 5'9" or a hair less. Any input would be nice. I think my wind scaling is good but I will do another out and back to triple check it.
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racerfern
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Re: cda questions.

Post by racerfern »

Rather than increasing the CdA I recommend you double check your wind scaling. A slight increase in wind scaling should bring those -37 to -67 numbers in line. Note that -37 to -67 is not extreme So you're not talking a big change here.
Fernando
Velocomp
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Re: cda questions.

Post by Velocomp »

In all of these kinds of questions, providing a ride file would be very helpful. Not only can we provide more specific help, but hopefully we can also teach you more about your iBike!
John Hamann
GWPOS
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Re: cda questions.

Post by GWPOS »

Ok here is a ride cal file and another ride file with an out and back. the first 2 cal rides I did came up with a wind scaling of around .750 or so. Then I did another cal ride and came up with numbers like .809- .811 so that is what I have been using. Now I did a recovery ride that had an out and back in it and it is giving me .925. Maybe my unit is just breaking in???/HAhaha. I posted my cal ride and last ride file.
iBike_06_21_2012_1125_6_Miles_CalRide.ibr
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iBike_06_24_2012_0809_22_Miles.ibr
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GWPOS
Posts: 178
Joined: Mon Aug 24, 2009 2:47 pm
Location: Yucaipa, Ca

Re: cda questions.

Post by GWPOS »

Here are my first cal rides and a couple of short out and backs. Would appreciate it if someone could make some sense of this to help me out with the wind scaling. Between my last rides and first rides I am not seeing a lot of consistancy. Thanks
iBike_06_21_2012_0710_2_Miles.ibr
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iBike_06_21_2012_0703_2_Miles.ibr
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iBike_06_21_2012_0628_4_Miles_CalRide.ibr
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Velocomp
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Re: cda questions.

Post by Velocomp »

I've looked at all your ride files.

You have done four (and maybe 5) calibration rides. In my view that is 3-4 too many.

No measurement instrument will measure exactly the same result, time after time. Your WSF varies from .70, .765, .783, and .834.

I would use .78 and be done with it.

However, you've changed your CdA from .35 to .533 in two of the rides. That is a HUGE change and it makes no sense.

Interestingly your 22 mile ride has a fifth WSF (.811) and your CdA is 0.379!

It looks like your Newton is being "tweaked" constantly. Neither the Newton nor the Isaac software can overcome this kind of user change.

I strongly recommend you spend your time riding your bike, with a single, unchanging profile.
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John Hamann
GWPOS
Posts: 178
Joined: Mon Aug 24, 2009 2:47 pm
Location: Yucaipa, Ca

Re: cda questions.

Post by GWPOS »

I know the files look like I did a lot. the cda of .500+ came from doing the coast downs after a cal ride. I threw that profile away, sorry I re-sent it to you. I was haveing issues though with the profile that was set by doing the fast start procedure. It set everything ok like my cda. .350 , wind scaling .811 tilt -0.7. Everything was looking great except for low numbers on various types of downhills. So I was just trying to fix my cda to reflect a more accurate number on those types of areas on my rides. I will keep it short. Today I did a cal ride on a bike path with no one there, no cars or anything. I ended up with wind scaling at .914. I am ignoring my first cal rides because they kind of got confusing.
Here is my profile.
aero .321
wind scaling .914
cda .351

fric 10.701
tilt -0.7
crr .60
How do these numbers look? I have attached this last "one or more to many" cal ride.

The only reason I tweaked my profile was because I was getting "-120+" watts when coasting downhill on the "coast" screen, when my cda was .350 and wind scaling was at .811. I raised my cda alittle at a time but when I got it to .379 I stopped. I was still getting around "-37-67 constantly while in the caost screen. Racerfern said that my scaling may be off so that is why I did this last cal ride. I left everything the way the fast start sequence set it and will try it out on a ride tonight.
iBike_06_25_2012_1151_4_Miles_CalRide.ibr
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