leonsrocketcar wrote:So I think I might be doing something out of whack: I am at 69' sea level. Ibike varies based on temp and blah blah blah. It got to a point that I just zero'd it out each time, The last 3 rides I put back the correct reading of 69, then did my offset and tilt.
Travis, are you saying in the quote above that I need to use the same altimeter settings on every CD/4m and ride? Otherwise I get the weird readings, albeit all other nuances done correctly?
I'm not sure if I understand what you are asking. If you are talking about setting the starting elevation, it is good to get the set in the right ballpark, but it is not critically important to the calculations. What is more important is to check and redo as necessary the tilt cal and the wind offset.
leonsrocketcar wrote:My last 3 rides have the tilt starting at 0 and straight line down for the length of the ride, i.e., -600'. Just like in my first post above. I checked the mount and it is cranked down.
You should find that that -600' is a function of how far you ride. If each of your last 3 rides were the same distance, then that means each had the same tilt error. The screenshot your link shows an 1h 25m ride. I'll guestimate that to be 26 miles, which works out to a -0.44% tilt error.
Are you seeing approximately a -0.4% to -0.5% tilt error for each of your rides?
Do you redo (or at least verify) your tilt calibration before each ride?
Do you have a profile that is getting attached to your rides?
If all answers are yes, what I am saying is that it is likely that your profile has a bad riding tilt. That's the common denominator.
For a given rider, ride position, bike, and mount location, the riding tilt is about the same every day. For numbers, I weigh about 175 lbs, ride a Spec Tarmac in the drops, and have a handlebar mount. My riding tilt is about -0.6% for each ride including my calibration rides. If I were to look at the raw slope reading coming out of the iBike and compare it to the actual known profile, I would always find that the average slope is too low by -0.6% +/- 0.2. Since I did a good job doing my tilt calibration before my coastdowns & 4-mi ride, my profile shows that -0.6%. Whenever I download a ride from the iBike and the iBike2 software attaches the appropriate profile, that -0.6% riding tilt gets subtracted from the slope for the ride. So if the day's ride was an out-and-back and the raw slope average was -0.53%, what I see in the advanced tilt window is a green line in the top plot that goes up mildly with a tilt error of only 0.07% after the -0.6% riding tilt in the profile get subtracted from the day's slope data. For the next 3 rides, I might get raw slopes of -0.71%, -0.52%, and -0.61%. After the profile gets attached, those work out to -0.11%, 0.08%, and -0.01% respectively. All of these are typical numbers for me. In each case, I would expect to see the bottom green plot be about 0.0% after the tilt correction for these out-and-back rides.
Now if I messed up the tilt calibration on the day that I did my calibration rides and a riding tilt of -0.16% got stored in my profile, then those three rides above with average raw slopes of -0.71%, -0.52%, and -0.61% would end up being -0.55%, -0.36%, and -0.45% top green lines and eventually I would start wondering why does my top green line always goes down about -0.44%. The answer would be because I screwed up the tilt calibration on the day that I did my calibration rides.
Travis
)? Then the correction shows a straight line. Is there a cheat sheet that explains in words and pictorial all the advance settings?
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