How often do you recalibrate your Power Meter?
 

As per a previous thread of mine I was getting some weird results from my 4iiii single sided PM. After a recalibration of the 4iiii and Garmin 530 it seemed to resolve itself and I got about 3-4 more trouble free rides in without any problems. Then, 3 days later I noticed that the Garmin was not reporting anything close to what I was doing. I had calibrated the 4iiii crankarm about 2 days earlier so I figured maybe there's something wrong with the Garmin Edge 530 so at the halfway point I recalibrated the head unit and it performed flawlessly for the remainder of the ride home. It appears that the problem is with the Garmin 530 and not the actual PM.

So, for right now it looks like I may need to do a recalibration on the Garmin before each ride. Is this out of the ordinary?

I think it is out of the ordinary, especially since the issue has evolved from functional to not. Some ideas; replace the battery in the PM, reset the Garmin to default and re-install the last SW update. Good luck.
Note; with my 4iii PM, I had to lightly abrade the battery for reliable function. I think this removes the anti-swallowing coating.

I will be swapping out the battery. The 4iiii app says it's 90% but we'll still do the swap to see what happens. Both the PM and 530 have the most current and updated versions and everything seems to work as expected. After the battery I'm going to give it 1 more chance and if it continues I'll be looking for the RMA email I was sent when I experienced the first problem. I do realize that there is a pattern here but I wanted to give it every opportunity to resolve itself before having to send it back. Right now everything is pointing towards the 530 and not the PM. Still....

In answer to the title question, I redo the zero offset before every ride (PowerTap hub and SRM crank). Other than older SRMs, I don't know of any power meters that can be user calibrated.

^^ Yes, that is what I mean "Zero Offset" for the 4iiii and on the Garmin it is titled "Calibrate" ^^

I first Zero Offset the 4iiii and then I Calibrate the Garmin (the Garmin has numerical a readout as to the calibrations success). The reason I started this thread was because I've seen some voices on the internet that say it is important to "Calibrate" the Garmin before every ride, and others don't say anything about it at all. I'm going to give it another chance i.e. battery change, zero offset and calibrate and if I see any more glitches it's going back. As I said, I'd like to exhaust all avenues before sending it back. I realize that sending it back may not only be unavoidable, but necessary. I just want to cover all my bases first.

The "Calibrate" on the Garmin doesn't calibrate the head unit -- it sends a signal to the power meter to re-zero.

Everything you've written is consistent with the 4iiii being the issue.

I’ve always used the 4iiii App to set zero and usually do this once every few weeks. I have never seen any big changes in the values like you have.

I rotate my cranks at least four times and end with the drive side pointing up before every ride. Mostly just to make sure it's woke up and connects to my Edge 530 that's already on and finding all the other stuff I'm turning on. I don't do anything with Garmin's calibration page for it. I've never had any odd ball issues or same rides that have different average power that I can't reason out by speed, winds or riding with others vs solo.

If your route is on the road and you are solo, have you considered how often you might have cars and trucks in front or constantly passing you on one ride and not on another? You'll get the benefit of a draft for quite a ways behind even when you aren't anywhere near the same speed.

I have Favero Assioma Uno pedals. Favero provides an iPhone app to do calibration. It takes about 15 seconds.

I remember calibrating them when I installed them a few years ago. That might be the last time.

How often are you supposed to recalibrate power sensors?

That depends on how much you care about the accuracy of your data. I'd say if accuracy is important (and if it isn't why would one bother with a powermeter) then reset zero at least at the start of every ride.

I used to do a static calibration check about every six months but after a while it became clear that it wasn't necessary as long as power readings weren't obviously wrong.

https://cimg1.ibsrv.net/gimg/bikefor...d0b2b152ea.png

Cruised out to my turnaround point with steady cadence. Then did my intervals on the way back. There were no "variables" on the ride going out.

Zero offset your power meter before every ride, after allowing a few minutes for your bike/power meter to settle in the ambient temperature you'll be riding in. Note that this is different to calibrating which requires a bunch of calculations, and known, certfied masses to hang off the pedals so that you can check the frequency response against the calculated response.

Calibration is important. I do zero offset before the ride and then again after warmup is complete. Calibration, with respect to is the power meter accurate after zero offset calibration is also important. All measuring devices require routine calibration. This is true for complex, accurate laboratory equipment as well as power meters.

I zero offset before every ride. When I switch on my Garmin it pops up a "Calibrate Power Meter" option, so I tap it. Takes 5-10 seconds.


The Garmin in theory should only report the number that is sent to it by the connected powermeter, no alteration of that data. Have you checked for firmware updates for your 4iiii powermeter? I think older firmware versions had some issues with cadence readings, and potentially power reporting because of this. Worth a shot.

It has already been replaced by 4iii

It's somewhat of an aside, but it's nifty that Favero Assioma calibrate/zero offset automatically. It can be done manually, but the automatic procedure will overwrite the manual values, so there is no need or point in doing it manually. It feels weird not doing it now, but I'll get used to it!

4iiii failure
Was your 4iiii showing extremely wrong data, like 25w where it should be 180? I think that's what mine did, a few weeks before it failed completely. This was early in 2020, and it was 3 or 4 months out of warranty. 4iiii didn't help out with a discounted replacement or anything. Very disappointing.

I got a Stages to replace it, and that reports better data anyway with no more 1-second-long extreme watts. I used to sometimes have to edit the extreme numbers out of the tcx data, which was annoying.

I calibrate it before most rides, but the reported calibration number, around 850 or so, is usually quite similar to other calibrations. it seems pretty stable.