New 4iiii Precision 3 Power Meter (2022 release)

I’ve had the 4iiii Precision 3 since the end of April and I’ve had no issues at all. Firmware was updated after unboxing and not since. It’s been every bit as reliable as the stages left arm on a different bike. As for accuracy, I use it train outdoors and readings on intervals all feel as expected between 4iiii, stages, and a tacx bike.

Maybe I’m lucky. Maybe I’m not good enough to notice a difference. Regardless, I have no worries in using this.

Yeah, then a 4iiii isn’t ideal. Here is my experience with it:

  • I have had two units, one was new, the other I bought used.
  • The first one produced wonky power data for two weeks (it gave me an average power of 400+ W on a ride and peak power values of 1,900+ W — needless to say, I’m not a pro :wink:). After a month it settled in and produced good data that I could train by.
  • I trained on a 4iiii for several years and I got stronger.
  • Second huge caveat: I have evidence that the 4iiii caused me to produce power more and more asymmetrically: to lift the power number displayed by 2 W, my left leg just needed to produce 1 W more (since the left power value is doubled). This is not an issue with the 4iiii specifically, but all one-sided power meters, though. According to the Quarq I’m back to balanced (it varies from 48:52 to 52:48 most of the time).
  • I’d still use one-sided power meters to record accurate TSS values or pace myself, but I would not want to train on them if possible.
  • The second 4iiii unit which I bought used died soon after arrival. Since this was a used unit, I am not sure it is fair to complain too much. But still, the unit and the crank arm looked pristine, so I don’t think the previous owner abused it.
  • In training I ran into an issue with cadence: the 4iiii tops out at about 160 rpm. During high-speed cadence drills I would exceed that. The 4iiii would just then display 0 power. The Quarq manages over 200 rpm.

Compare that to my experience with the Quarq:

  • Day 1: inserted battery and got reliable power numbers.
  • About 6 months later: needed to replace the battery, battery died suddenly during a ride. Zero dropouts or wonky power numbers until then.
  • About 15 months after purchase: battery low again, needs replacing. Zero dropouts, no funny power numbers.
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Thanks! I considered quark dfour but I’d need a new bb for that. I have praxis t47 shimano bb.

Sorry off 4iiii topic…I also am considering power2max grx chainline is similar and fits 24mm bb but the q factor is 147mm vs grx 151mm. It is a concern because I’ll be using the grx di2 front derailleur and basing off this forum (Crankarms awfully close to FD... - The Paceline Forum) it seems too close for comfort. There’s no way to increase gap unless I use road derailleur I think and no idea how well shifting with grx di2 system. P2max told me no way to increase Q factor without longer spindle with Rotor that is not available. Can’t use spacers either? He mention spacers on pedals but that doesn’t pull crankarm outwards away from front derailleur.

I’m a bit frustrated trying to find a system that works. My wish was that the 4iiii would be it. Maybe gen 2 is more reliable bet?

The road FD is not suited, it is not designed to shift chain rings smaller than 50 teeth (for the bigger one). You’d need an adapter and even then the Di2 gobbins may rub against the tire. Rides of Japan did just that in a recent video to get 47/32 chain rings to fit. He had to downsize the tire to make it fit.

BBs aren’t that expensive in the grand scheme of things.

oh i see. thank you for pointing that out. ya i emailed PMC and they told me q factor won’t be same as grx. i really wonder if q factor is issue in the end. from what i understand is its distance from outer crankarm to outer crankarm. so if a 147mm q factor vs 151mm wouldn’t this move the crankarm out by 2mm each side, further outward and away from front derailleur too?

if you can find me a $50> BB for my traildonkey 3.1 then i might consider quarq :stuck_out_tongue: still would want to confirm clearance and shifting quality. what is the qfactor and chainline btw?

did you see how close that guy’s crankarm was to the front derailleur? (note: i emailed P2M as well, they said GRX di2 front mech has a little more clearance than the GRX mechanical front mech. but didn’t confirm spacing, which gives me a little hope if considering P2M)

With a Quarq DFour you can use Shimano chain rings. And then shifting is identical to GRX because you are using Shimano chain rings. You could use third-party chain rings (e. g. by Rotor), too, and then you might get different shifting quality. I’ve only had the opportunity to use Rotor chain rings for a bit, and they shifted great (even though they were oval chain rings).

I don’t know, but I reckon more in line with a road group set.

i got in touch with PMC and they told me I can’t use the quarq dfour, GRX different bcd, and cant use those chainrings. I’d have to use at least compact cranks or use a smaller bcd version of quarq. the chainline would be road-like so I’m not sure if that would work well in my case. if i can find someone in this world who is riding my exact group, otherwise i don’t want to risk it. still deciding on power2max though since they have the 24mm spindle. i’m also in touch with 4iiii on their update for next firmware on Precision 3 though.