Slope issue

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brookside
Posts: 48
Joined: Tue May 05, 2015 7:03 am

Slope issue

Post by brookside »

Not sure if this should be here or in the Newton Setup forum...

Moved the Newton (FW5) to a new bike yesterday and did a Calibration ride, looked like it completed successfully. Then started from my usual place and immediately noticed it was showing 0 watts. Checked the slope and it said I was descending a 1 to 2% hill when in fact I was going up a 4 to 5% incline (per previous Newton readings and ridewithgps estimates). After about 11 or 12 minutes, at the first stop I came to, it seemed to get itself together and after that the slope readings made more sense, although they were still at times 1 to 2% off at certain places vs. the Newton's previous readings on two other bikes, usually exaggerating downhill slopes. In general the slope readings seemed off the whole way.

When I looked at the main ride file in Issac it had corrected the slope data for that first bit of a climb but then showed negative slope, and close to 0 watts, from about mile 1.3 to 2.7 when in fact it's almost all up a slight grade (as the Elevation window correctly shows).

I also noticed that at some stops the slope would at first spike 4 to 6 degrees, usually in the direction of the prevailing slope, then after 5 seconds or so settle back to a reasonable number.

Doesn't the Cal ride set the tilt? Do I need to do another Cal ride or is there some other way to sort this out? Ride files attached if that helps. Ride was on a TT bike in the aero position with Newton attached to aero bars and using a RWS.
Attachments
iBike_05_04_2015_1403_3_Miles_CalRide.ibr
(43.06 KiB) Downloaded 267 times
iBike_05_04_2015_1413_24_Miles.ibr
(278.91 KiB) Downloaded 256 times
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Slope issue

Post by Velocomp »

Your calibration ride should have set the "tilt offset" parameter so that your next ride would be correct right from the start.

The calibration ride worked; I can see this by examining your profile.

However, your "tilt offset" parameter was way off at the beginning of your 24 mile ride.

By any chance, is it possible to rotate your Newton on your bike? This would account for the incorrect tilt offset parameter...

Note that, after 7 minutes of riding the Newton self-corrected and all was well.

The corrected tilt offset was saved at the end of your ride, so you should get good results on the next ride, right from the beginning.

As we explain in the instructions, the slope will change due to changes in bike speed, such as happen when you stop or accelerate the bike.
John Hamann
brookside
Posts: 48
Joined: Tue May 05, 2015 7:03 am

Re: Slope issue

Post by brookside »

When you say rotate the Newton I guess you're asking if the mount rotates, which it doesn't. It's a TT mount attached to the aerobars, so any rotation would be left/right rather than forward/back. While firmly secured it does have a slight tilt to the left that I gave up trying to adjust out when installing the mount, but I could work on that some more if it's the cause of the bad tilt.

A related observation, when I was switching the Newton back and forth between two other road bikes the slope would be off sometimes 5 or 6 % at the start of each ride even though I had selected the correct profile for that bike, and had done a Cal ride for each. It would correct itself after 6 to 8 minutes.

Also, the Newton slope reading lags the actual slope by 5 to 10 seconds or so, both on the Newton in real time and on the Isaac charts (e.g. at the point the elevation window shows the top of a hill has been slightly passed the slope window is still showing a upward slope), is this normal?

Thanks,
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