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Power Meter is way off

Old 09-19-23, 12:18 PM
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Power Meter is way off

Up until today's ride the PM on my new Canyon Endurace (4iiii) has been reporting power that is inline with what I was seeing with my previous Endurace with the same model PM. Today, on a more casual ride with a friend my watts were showing as 40 points higher than normal. My Garmin recorded today as the best PM Curve I've ever had. I was not pushing it at all and something is really off. When I got home I recalibrated the PM and went for a quick trip up and down the block and it was still reporting back way too high. My HR, Cadence and Speed confirm that today was nothing out of the ordinary. Since this bike is new with only about 350 miles on it I'd like to find out if this is something that others have experienced and if I should remove the crankarm and possibly request an RMA?
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Old 09-19-23, 03:02 PM
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If you bought it with the 4iii from Canyon, I'd ask them what they think you need to do to. If you bought the PM from 4iii, then ask them. They usually answer my questions. Sometimes takes them awhile to respond though.

Not a case of your friend not pulling their fair share during the ride is it? Bikes are pretty much the same weight?
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Old 09-20-23, 07:17 AM
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I've got an email out to 4iiii customer service and see what they say. I wasn't sure if this was the correct forum for it but since most people who "train" frequent this area I thought someone might have seen this before. There seems to be a lot of Band-Aid solutions that work, but in their FAQ section they say if you're seeing really big jumps to contact them. My NP (and everything else) went up a little over 40 watts compared to the previous days hard ride and that was just not right. I have all the other metrics i.e. HR, cadence and speed to show that it wasn't the effort the PM is showing.
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Old 09-20-23, 10:23 AM
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Yeah it sounds odd. One thing I would try is a fresh battery. I have had mine give odd power readings on a low battery and it was pretty sudden.
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Old 09-20-23, 11:06 AM
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Originally Posted by TakingMyTime
I've got an email out to 4iiii customer service and see what they say. I wasn't sure if this was the correct forum for it but since most people who "train" frequent this area I thought someone might have seen this before. There seems to be a lot of Band-Aid solutions that work, but in their FAQ section they say if you're seeing really big jumps to contact them. My NP (and everything else) went up a little over 40 watts compared to the previous days hard ride and that was just not right. I have all the other metrics i.e. HR, cadence and speed to show that it wasn't the effort the PM is showing.
I'm not disputing that the pm may be at fault, but none of these are as consistent or reliable as power. HR variability from day to day can be quite large - hydration, rest state, nutrition, etc. (caffeine?), all cause significant day to day changes. speed depends on terrain, wind, drafting, and more. Cadence is not much help unless you are also recording the corresponding gear ratios.
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Old 09-20-23, 11:27 AM
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Originally Posted by MinnMan
I'm not disputing that the pm may be at fault, but none of these are as consistent or reliable as power. HR variability from day to day can be quite large - hydration, rest state, nutrition, etc. (caffeine?), all cause significant day to day changes. speed depends on terrain, wind, drafting, and more. Cadence is not much help unless you are also recording the corresponding gear ratios.
40 watts (which is the difference the OP is seeing) is a lot. If you have a reliable and precise measurement of speed (e.g., wheel sensor) and you regularly use the same route, you can often tell whether a power meter is off by that much. Sometimes you can use reported speed and reported cadence to tell if the accelerometers in the crank arm is off. I wouldn't use HR to try to validate a PM.
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Old 09-20-23, 12:11 PM
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Originally Posted by MinnMan
I'm not disputing that the pm may be at fault, but none of these are as consistent or reliable as power. HR variability from day to day can be quite large - hydration, rest state, nutrition, etc. (caffeine?), all cause significant day to day changes. speed depends on terrain, wind, drafting, and more. Cadence is not much help unless you are also recording the corresponding gear ratios.
For me 40W difference in average power on a ride would be night and day in perceived effort. The other metrics might not be consistent from day to day, but average power is pretty consistent for the same perceived effort. If I suddenly found myself 40W up without trying a LOT harder I would know it was bs.
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Old 09-20-23, 02:12 PM
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Originally Posted by PeteHski
For me 40W difference in average power on a ride would be night and day in perceived effort.
Same here. My buddy and I were riding back home when I decided to change the screens on my Garmin so I could see my power results and when the screen came up it looked as if I was crushing every record I ever had. Defiantly something wrong.

I was also concerned (as mentioned above) that temps and other variables may be causing these results. The good news is that 4iiii in Canada, after looking at the additional metrics I sent them along with the wattage results are giving me an RMA opportunity so that they can further examine and test the unit.

"Unfortunately, this unit cannot be diagnosed further by our customer service team. Your crank will need to be returned to our HQ factory in Canada to be repaired. Please complete the Return Merchandise Authorization (RMA) form attached to this link:"

They are covering all costs. My only regret is that I won't have a bike to ride for probably at least 2 weeks. I'm going on a ride tomorrow and I will test the unit one more time before sending it back. I'll also have to find another NDS crank arm. I'd hate to lose 2 weeks or riding.
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Old 09-21-23, 01:04 PM
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Originally Posted by TakingMyTime
They are covering all costs. My only regret is that I won't have a bike to ride for probably at least 2 weeks. I'm going on a ride tomorrow and I will test the unit one more time before sending it back. I'll also have to find another NDS crank arm. I'd hate to lose 2 weeks or riding.
Assuming this a a Shimano road bike hollowtech crank arm, then any hollowtech left crank arm or right crank/spider will do. The shades of black and the profile might be different, but the connection is the same.

I currently run a 105 5800 drive side crank/spider with Ultegra R8000 rings and left side crank. The profile of the rings doesn't match the spider. But if you can tell that as you ride next to me, then you have much better eyes than I do. And are looking where you shouldn't be. Eyes on the road!
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Old 10-03-23, 07:07 AM
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As a follow up... I decided to run the PM on several more rides and it seems to have settled back to normal after that 1 day anomaly. Ever since then I'm getting results where I would expect them to be. Because of that I wrote 4iiii and let them know I wouldn't be sending it back. Everything looks good for now. I've been on 6 more rides since then and things are fine.
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