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50 watt discrepancy between trainer and outside

Posted: Sun Mar 10, 2013 2:20 pm
by toddk
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

Re: 50 watt discrepancy between trainer and outside

Posted: Sun Mar 10, 2013 5:06 pm
by Velocomp
Please post your outdoor ride file.

Re: 50 watt discrepancy between trainer and outside

Posted: Sun Mar 10, 2013 9:06 pm
by toddk
Here is the outdoor ride file.

Thank you.

Re: 50 watt discrepancy between trainer and outside

Posted: Mon Mar 11, 2013 3:47 pm
by Velocomp
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.

Re: 50 watt discrepancy between trainer and outside

Posted: Mon Mar 11, 2013 8:36 pm
by toddk
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!

Re: 50 watt discrepancy between trainer and outside

Posted: Mon Mar 11, 2013 9:34 pm
by toddk
photo(2).JPG
photo(2).JPG (114.55 KiB) Viewed 14530 times
mounting pics , needed place 1 in. spacer ..(not sure if this helps, just want to rule anything out)

thank you

Re: 50 watt discrepancy between trainer and outside

Posted: Wed Mar 13, 2013 12:50 pm
by toddk
any thoughts?

Re: 50 watt discrepancy between trainer and outside

Posted: Wed Mar 13, 2013 8:25 pm
by racerfern
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.

Re: 50 watt discrepancy between trainer and outside

Posted: Wed Mar 13, 2013 9:51 pm
by toddk
Thanks for responding Fernando I shall give it a try!

Re: 50 watt discrepancy between trainer and outside

Posted: Thu Mar 14, 2013 8:12 pm
by toddk
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?

Re: 50 watt discrepancy between trainer and outside

Posted: Thu Mar 14, 2013 9:44 pm
by Velocomp
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.

Re: 50 watt discrepancy between trainer and outside

Posted: Sat Mar 16, 2013 9:57 am
by toddk
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.