Testing Power Meters. 4IIII is way off vs H3 and Garmin Rally

So I have 2 Saris H3’s that match very close to eachother for power. I had been using powermatch off my 4iiii left side 105 crank. I know have the garmin Rally Vector pedals for another bike but I thought I would try them on this bike for a test. The Rally’s will mainly be used outside for the season and the crank will be used inside on my road bike for the winter.
Is there anyway to adjust the calibration of the 4IIII to make it similar to everything else.

I have run some numbers:

4IIII is around 20 watts high over the H3 and garmin rally 200 for this test on average. I believe it is actually higher as things were manually started pressing buttons and timing may be off.
Rally is around .27 watts higher than the H3 over the same period on average.

I may just need to use the 4IIII for cadence but I would like to get it reading more accurately for outside next season

Disappointing about the instantaneous 20-30 watt power loss lol :wink:

I would like to know if there is anyway to adjust the 4IIII to what the other 3 devices are reporting.

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The PM that reads the highest is the most accurate!

Perhaps you have a very dominating left leg? How does the L/R balance look on the pedals?


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The 4iiii app might let you easily adjust it. I would check for you but its bed time UK time, g’night :+1:

Looks like I am 52.75 left.

Have you tightened the 4iiii 105 crank pinch-bolts with a torque wrench? (12-14Nm iirc)


It was installed at a shop. Thanks for the tip Shane! Now I need to find a decent but not ridiculous priced torque wrench!


I own a few from Harbor Freight. Not bad for $20, but then again I have no way of knowing how accurate they are.

Single sided left was pretty good. 4iiii Precision Power Meter (LEFT Side Shimano): Details // Data Review - YouTube


I just got a Garmin Rally XC100 and noticed it reads a lot lower than my 4iiii precision left crank power meter.
So it seems 4iiii is in general higher.
Also sad about losing 40 watts FTP. At age 52 hard to gain back.

Is one a dual side power meter because the xc100s are single sided?