50 watt discrepancy between trainer and outside

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toddk
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Joined: Tue Jan 29, 2013 11:18 am

50 watt discrepancy between trainer and outside

Post by toddk » Sun Mar 10, 2013 2:20 pm

Can someone please review my profile? I am getting approximately 50 watt difference in FTP and average watts between indoor trainer ride (fluid2) and outside. The indoor trainer is the higher.

As an example my last 26 mile loop ride averaged 104 watts but 18.4 mph - seems like wattage a bit low?

I ride a Specialized Transition LE in time trial position.
Ibike dash + power w/ remote wind sensor.

I have performed the usual suspects - calibration ride, tilt calibration etc.

Thanks in advance for the help!!

Profile:

Rider Weight: 144
Bike + Other 23
Total: 167

Tire Circumference: 700x23c (2096mm)


Aero: 0.164
Wind Scaling: .6659
CdA: .247


Crr: .0055
Friction: 1.118
Riding Tilt: 0.4%

Wind Scaling: .6659

Velocomp
Velocomp CEO
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Joined: Fri Jan 11, 2008 8:43 am

Re: 50 watt discrepancy between trainer and outside

Post by Velocomp » Sun Mar 10, 2013 5:06 pm

Please post your outdoor ride file.
John Hamann

toddk
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Re: 50 watt discrepancy between trainer and outside

Post by toddk » Sun Mar 10, 2013 9:06 pm

Here is the outdoor ride file.

Thank you.
Attachments
iDash_2013_03_09_0821_27_mi.ibd
(128.46 KiB) Downloaded 170 times

Velocomp
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Re: 50 watt discrepancy between trainer and outside

Post by Velocomp » Mon Mar 11, 2013 3:47 pm

toddk wrote:Here is the outdoor ride file.

Thank you.
Wow, it's almost as flat where you live as it is in Florida!

You have a very low drag coefficient; please confirm that you are using a TT bike, and also provide your height.

Also, your ride file suggests that you are riding in the draft quite often. Is this correct?

Finally, the total weight of bike + rider is 167 pounds, suggesting that your body weight is about 144 pounds. Correct?

Given these input parameters, your Newton is reporting correct wattage for your speed and riding conditions.
John Hamann

toddk
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Re: 50 watt discrepancy between trainer and outside

Post by toddk » Mon Mar 11, 2013 8:36 pm

Confirmed - TT bike .

Height 5ft 10.5 in
weight correct

No drafting, i ride solo... The wind #'s seem low. The weather said 12 mph winds that day , but my readout suggested otherwise

Your right , houston and florida ...very flat...and hot...and humid 8)

FWIW i'm using the ibike dash + power.

I will attach a picture of mounting - not sure if that influence #'s

Thanks in advance!
Last edited by toddk on Mon Mar 11, 2013 10:47 pm, edited 1 time in total.

toddk
Posts: 8
Joined: Tue Jan 29, 2013 11:18 am

Re: 50 watt discrepancy between trainer and outside

Post by toddk » Mon Mar 11, 2013 9:34 pm

photo(2).JPG
photo(2).JPG (114.55 KiB) Viewed 4294 times
mounting pics , needed place 1 in. spacer ..(not sure if this helps, just want to rule anything out)

thank you
Attachments
photo(3).JPG
photo(3).JPG (44.44 KiB) Viewed 4275 times

toddk
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Re: 50 watt discrepancy between trainer and outside

Post by toddk » Wed Mar 13, 2013 12:50 pm

any thoughts?

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racerfern
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Location: Baldwin, NY
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Re: 50 watt discrepancy between trainer and outside

Post by racerfern » Wed Mar 13, 2013 8:25 pm

I took a look at the ride file and based on your statement that you are not drafting I would raise the wind scaling to .912. I would also suggest you do another cal ride to confirm the ride tilt of .4 as I would be inclined to think about -.1 for your size on a TT bike. However the change in riding tilt is only three watts. The big thing is the wind scaling.

Try the attached profile, it will raise your avg from 109 to 127 and should be just about right based on your info.
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toddk_mod_profile.ibp
(481 Bytes) Downloaded 160 times
Fernando

toddk
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Re: 50 watt discrepancy between trainer and outside

Post by toddk » Wed Mar 13, 2013 9:51 pm

Thanks for responding Fernando I shall give it a try!

toddk
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Joined: Tue Jan 29, 2013 11:18 am

Re: 50 watt discrepancy between trainer and outside

Post by toddk » Thu Mar 14, 2013 8:12 pm

For best results with the dash + power, should I wait till for a nearly 0 wind ? If there is wind should I ride in cross/head...does it matter?

Velocomp
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Re: 50 watt discrepancy between trainer and outside

Post by Velocomp » Thu Mar 14, 2013 9:44 pm

toddk wrote:
photo(2).JPG
mounting pics , needed place 1 in. spacer ..(not sure if this helps, just want to rule anything out)

thank you
You're using your + Power in a TT position, but without a Remote Wind Sensor.

Your problem may be that you're getting unstable wind readings because of your arms.

An RWS may take care of everything.
John Hamann

toddk
Posts: 8
Joined: Tue Jan 29, 2013 11:18 am

Re: 50 watt discrepancy between trainer and outside

Post by toddk » Sat Mar 16, 2013 9:57 am

Hi John,

I actually am using an RWS. I've uploaded the latest version of firmware for + power, reinstalled and will redo a calibration ride. Not sure why it is not picking up the RWS, hopefully the latest firmware , reinstall, and new calibration ride will resolve. We shall see...

Thanks again , FWIW , really enjoying ibike it on the trainer 8) , making some nice gains in the FTP, just looking forward to getting the outdoor rides sorted.

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