After many months of wrestling with cal rides and profiles and seeming to get really wonky power numbers, I decided to cave and just use a quick start profile. Once I did, everything seemed about right and I was happy with the numbers. Except for one thing: descents. If I'm pedalling, the power numbers go through the roof! The only thing I can think of is there is something wrong with the tilt given that all of the other parameters are predetermined. I've tried doing tilt calc but the numbers don't change when I extract the profile after the tilt calc is done. Does anyone have any suggestions or ideas? I've included the profile if anyone would care to take a look and help me out.
Thanks.
Crazy high power on descents
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andrewlees
- Posts: 31
- Joined: Tue May 07, 2013 1:43 pm
Crazy high power on descents
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- Profile June 15, 2013.ibp
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Re: Crazy high power on descents
well this is interesting in that you seem to have a high wind scale and a high aero number etc and it would be interesting to hear from someone with more experience. On the other hand there is a reason for high power numbers going down hill. When you increase your speed the amount of power to over come aerodynamics goes up at a nonlinear rate (the function has the rate of speed squared). So typically when not pedalling coasting downhill, this is not an issue. When you pedal then the 3 factors that go together to make up total power add up pretty fas, you have kinetic energy going down hill so you have gravitational speed, so there is no gravitational power to overcome you make up for that in the aerodynamic aspect where speed really means it takes a lot of power to gain a small amount of speed at say 50 or 60 KPH. So the meter is working fine but I am curious about your settings though especially the aero value in your set up, since that will definitely impact the aero aspect of of the power at higher speeds.
Re: Crazy high power on descents
Your profile looks pretty much on the money other than the WS is toward the high side but not off the scale. Where is Newton on the handlebar or stem? Can you upload some out/back ride or just a regular ride that contains these spikes. Spikes on downhills are usually for very short periods and really don't affect the overall numbers but we'll have to see an example.andrewlees wrote:After many months of wrestling with cal rides and profiles and seeming to get really wonky power numbers, I decided to cave and just use a quick start profile. Once I did, everything seemed about right and I was happy with the numbers. Except for one thing: descents. If I'm pedalling, the power numbers go through the roof! The only thing I can think of is there is something wrong with the tilt given that all of the other parameters are predetermined. I've tried doing tilt calc but the numbers don't change when I extract the profile after the tilt calc is done. Does anyone have any suggestions or ideas? I've included the profile if anyone would care to take a look and help me out.
Thanks.
Fernando
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andrewlees
- Posts: 31
- Joined: Tue May 07, 2013 1:43 pm
Re: Crazy high power on descents
Thanks for the insight guys.
Fernando, I've attached 2 rides. One (06_15_2013) where I specifically went and rode fairly hard over the top and down the other side of a hill. Around 19km, you can see the large spike. And the Newton is on the bar. Then the other (06_18_2013) where I was going moderately hard for about starting at 49km for 10 mins and created my best 5 and 10 min powers ever!! This one, my HR is so low for the power produced.
With regards to the wind scale, what's the fix and what's a normal number? This is one aspect of the Newton that has actually caused me the most confusion.
Keep in mind, all the factors are default numbers for my weight, height, tires, position etc.
Andrew
Fernando, I've attached 2 rides. One (06_15_2013) where I specifically went and rode fairly hard over the top and down the other side of a hill. Around 19km, you can see the large spike. And the Newton is on the bar. Then the other (06_18_2013) where I was going moderately hard for about starting at 49km for 10 mins and created my best 5 and 10 min powers ever!! This one, my HR is so low for the power produced.
With regards to the wind scale, what's the fix and what's a normal number? This is one aspect of the Newton that has actually caused me the most confusion.
Keep in mind, all the factors are default numbers for my weight, height, tires, position etc.
Andrew
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- iBike_06_18_2013_1738_75_km.ibr
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- iBike_06_15_2013_1245_61_km.ibr
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Re: Crazy high power on descents
I'm not saying there is anything with your wind scaling. Being on the bar its normal to have higher than 1.5 wind scaling. All I said was 2.2 was getting up there. That said, your wind scaling looks good so I wouldn't worry about it. Sorry if I caused you concern. However, I saw on another post that you had an issue with a cal ride. Have you solved that and done a good cal ride followed by an out/back? If so can you post it so we can have a look?
AFA the spike on the 15 June ride, I don't have a good explanation but I wouldn't worry about it either. It's such a tiny part of the overall mix that it changes nothing.
On the 18 Jun ride although your HR was low at the beginning of that downward slope, by the end of that downward run it had risen to the highest point in the ride. That's not easy to do on a downhill run and indicates a fairly concerted effort. I can't really tell that there's anything right or wrong here.
AFA the spike on the 15 June ride, I don't have a good explanation but I wouldn't worry about it either. It's such a tiny part of the overall mix that it changes nothing.
On the 18 Jun ride although your HR was low at the beginning of that downward slope, by the end of that downward run it had risen to the highest point in the ride. That's not easy to do on a downhill run and indicates a fairly concerted effort. I can't really tell that there's anything right or wrong here.
Fernando
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andrewlees
- Posts: 31
- Joined: Tue May 07, 2013 1:43 pm
Re: Crazy high power on descents
Fernando,
Here is the last Cal Ride I did. I would say I've done about 15 so far since having the Newton. They all generally have had some values relatively close to one another. This last one though, I had concern with I find the friction value to be about double what the all the other have had (generally they've been between 6 and 8; this one is 14). Earlier this spring, I had been doing these other cal rides beside a major river and as it was spring, the river was quite cold and occasionally, I could feel pockets or blasts of cold air if the wind was right, and I'm certain this change in air during the cal ride, was likely affecting the calibration. For this ride, I moved to a different location away from water and in a relatively open area so trees etc weren't creating a "drafting effect".
Here is the last Cal Ride I did. I would say I've done about 15 so far since having the Newton. They all generally have had some values relatively close to one another. This last one though, I had concern with I find the friction value to be about double what the all the other have had (generally they've been between 6 and 8; this one is 14). Earlier this spring, I had been doing these other cal rides beside a major river and as it was spring, the river was quite cold and occasionally, I could feel pockets or blasts of cold air if the wind was right, and I'm certain this change in air during the cal ride, was likely affecting the calibration. For this ride, I moved to a different location away from water and in a relatively open area so trees etc weren't creating a "drafting effect".
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- iBike_06_10_2013_1307_4_km_CalRide.ibr
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Re: Crazy high power on descents
There are several likely problems with your profile:
1) Your body weight is given as 133 pounds, and your total bike+gear weight as 15 pounds.
Based on the CdA shown in your ride file, with a rider weight of 133 lbs your height would be 5' 9". Please confirm that rider weight and height are correct
2) Your total weight for bike, gear (shoes, helmet, clothing, and water) is 15 pounds. This is very, very light--probably impossibly so. Please confirm correct bike+gear weight
3) Your calibration measures a wind scaling factor of 1.642, but your subsequent rides have a wind scaling factor of 2.20. 2.2 is a factory default for handlebar position. Most likely what happened is that, when you dialed-in your profile, you selected the "handlebar" position, instead of selecting "Use Cal Ride" choice. Your selection overwrote the measured result of 1.64
All of the above will cause real problems for your watts--and cause watts to be crazy-high on downhills (wind scaling is way too high).
Use the attached profile to get your Newton back to cal ride results. Also, importantly, use the Device/Setup Device... option to make any needed corrections to weights and height.
1) Your body weight is given as 133 pounds, and your total bike+gear weight as 15 pounds.
Based on the CdA shown in your ride file, with a rider weight of 133 lbs your height would be 5' 9". Please confirm that rider weight and height are correct
2) Your total weight for bike, gear (shoes, helmet, clothing, and water) is 15 pounds. This is very, very light--probably impossibly so. Please confirm correct bike+gear weight
3) Your calibration measures a wind scaling factor of 1.642, but your subsequent rides have a wind scaling factor of 2.20. 2.2 is a factory default for handlebar position. Most likely what happened is that, when you dialed-in your profile, you selected the "handlebar" position, instead of selecting "Use Cal Ride" choice. Your selection overwrote the measured result of 1.64
All of the above will cause real problems for your watts--and cause watts to be crazy-high on downhills (wind scaling is way too high).
Use the attached profile to get your Newton back to cal ride results. Also, importantly, use the Device/Setup Device... option to make any needed corrections to weights and height.
John Hamann