That about sums it up.
As my LBS said, “you’ll almost certainly never notice the difference, but if you ever get any knee/ankle niggles in the future you’ll always be wondering whether the unequal q-factor was a factor - so stick a couple of 1p washers in now to avoid that”.
Couldn’t argue with that!
I’m running the 4iiii dual on my Felt Breed 30 with the
Shimano GRX FC-RX810 11-Speed Crankset. No issues yet.
I just put a 105 stages left arm on my GRX 600, both purchases dictated by the lack of 165mm options for GRX 800 cranks.
The main reason I’m posting here is that I was a bit nervous about the chainstay clearance on my bike given it’s not a common frame. I think a possible rule of thumb people could use (but please make sure you can return whatever you buy!) is that a road crank arm will likely clear if your gravel bike has clearance for ~40mm tires. If you are riding a more modern gravel frame with clearance at 47+ then you are more likely to have issues
Nice thought. But that’s not how that works. It’s all about the shape of the chainstay. I have 50mm tire clearance and the left sided 4iiii power meter fits well. In my opinion the best way to figure the fit out is with a AAA battery as described from 4iiii:
Thank you for setting me straight before I confuse others.
I had seen that method, but it obviously is less helpful if you don’t have access to the frame (i.e. trying to select a frameset online). I tried asking, but that requires a manufacturer who will respond 
edit: in case anyone is searching google later - the cinelli zydeco has a good bit of clearance remaining with a 105 stages crank
You are right, thanks for the addition. I forgot about the pre frame purchase case. I remember how I tried to look online at pictures of my frame from all possible directions to figure it out. Obviously that didn’t work out 
but I was lucky. That’s also why I mentioned my frame earlier in the thread. I hope it helps someone who uses google to figure the compatibility of this specific frame / power meter combo out.
I recently purchased a Trek Checkpoint SL5 with a GRX610 crank set, no PM. I was thinking about the left-side only 4iiii or Stages left-side PM since they’re affordable.
Five years ago I ran a Gen-1 Stages left-side only PM on my road bike and was dissatisfied with it because it did not consistently report power from ride to ride. I eventually replaced it with a Quarq DZero which has been exceptionally reliable and consistent.
My question to those of you with the left-side only 4iiii or Stages is “Are you finding the power reporting to be consistent ride to ride?” Based on my prior experience with the Stages, I’m a little hesitant.
Any feedback you all provide is much appreciated. Thanks!
Gen2 Stages left only was consistent. Then I upgraded to gen3, it was consistent. New bike has Quarq and also consistent.
Thanks for the info. Have you been able to establish what the variation in power output is between your Stages and Quarq? Meaning do you have a sense (which I realize may be subjective) whether the two track power output similarly?
Thanks.
Subjectively they are tracking the same, and so I haven’t tried to compare the two bikes. I’ve been doing mid-week 2 hour zone2 rides and power:HR are the basically same between the two bikes (Stages gen3 dual on older bike, Quarq on new). Also no perceptible power differences on 5-sec hard efforts, sweet spot power:HR looks the same, and same subjectively and power:HR on short controlled vo2 work. Everything seems to basically line up. I’m doing my next field test on the new bike, and no plans to continue riding the old bike.
I just had (10 speed) GRX crank fitted to the bike, and had completely forgotten about the q factor difference. I didn’t notice at all (first ride) with my 105 4iiii fitted. I really don’t know whether I’m within 2mm when fitting cleats compared to old position, not to mention some float?
Thanks for the feedback. I’m looking into the Stages GRX Gen 3 left side, sold out everywhere for 172.5 mm crank.
4iiii has availability, but I don’t know much about their products. Have some reading to do. If anyone has experience with 4iiii left side only power meter, please share your experiences with respect to consistency and accuracy. Thanks.
Stages and 4iii are more similar than different. One technical difference is that 4iii allows you to manually adjust the slope and compensate for power meter differences between bikes. If you use one bike for indoor or outdoor workouts, that technical difference is likely a don’t care.
Ah, that’s interesting. Does this mean that it would be possible to adjust the slope so that I get similar readings to what my Quarq puts out? Thanks.
thats the idea, but keep in mind you are talking about one sided versus total power. Go read about the 40-50W difference between Quarq’s new one-sided Rival PM and Garmin Rally PM pedals. The issue turned out to be one-sided vs total power.
Thanks, I checked it out. I can accept a difference in power measurement, not inconsistency ride-to-ride, which is what I experienced with the Gen 1 Stages. Thanks for your all your help!
I have left only 4iiii on my old 105 crank swapped into GRX.
Consistency ride-to-ride seems good. Match between 4iiii and Direto Elite not as good (4iiii reads 4-8% lower, depending on where in the power curve I am). So I love the scaling feature in the 4iiii app, which gets them to agree very closely according to DCR’s Analyzer. Also, TR’s Powermatch has much improved, I hear, so might not even have to tweak the 4iiii.
Also, I really liked 4iiii support. The original from 4 years ago suddenly started giving this old fred Sagan numbers a couple years ago, just after warranty out. Precision waived warranty expiration and gave me a free replacement, which has kept working fine, day in and day out. Happy customer.
In your shoes (ho ho!) I probably wouldn’t worry about it.
My left-side 4iiii was installed by my LBS as part of a new bike build, and he’s a perfectionist. When I mentioned the q factor difference in passing he immediately said he’d shim it now so that if in future I ever experienced any left knee/ankle niggles (fit issues) we’d have ruled out q-factor imbalance as a potential cause. ie. more of a peace of mind thing, although I like his logic.
Fitting it myself I’d probably not have bothered.
I have 2 left-side 4iiii PMs, and have been super happy with them. They’ve both worked flawlessly with zero issues experienced.
I can’t speak to accuracy directly, as although I have a Neo trainer I’ve never used the 4iiii bikes on the Neo. However, the numbers I see on outdoor rides (from max efforts) tie in as expected with the Neo-sourced numbers, ie. the three sources all live together happily on my TR PR power curve with nothing unexpected ever noticed. I also never notice any consistency issues, and my overall experience has been as if I’m using a single PM source, not three.
For the price I paid for them I really could not be happier.
Thanks for your feedback. Looks like I’m not going to have enough clearance between the crank arm and the left chain stay according to 4iiii’s AAA battery test. I’m awaiting confirmation from their support stafff.
The one thing I have observed is their commitment to their customers is excellent. So many stories about 4iiii replacing out of warranty PMs.