Power meter for Roadie and Trainer usage

Looking for what would be best bet for me. I am leaning towards a 4iiii left only for the $350 price.

I do have an older Quarq PM (10 spd rings) that I was thinking about using, but have heard it won’t match up with the new Ultegra gearing or design. Not sure that is true.
If it will work, problem solved and I will just need to get a correct BB for the SL6.

If it doesn’t work, should I consider anything else? I don’t think I am too worried about the left only reading. I also am looking for a powermeter as I want to do TR indoors this winter and I currently only have an old school cycleops fluid 2 trainer. I know I can set up my bike on the old dumb trainer with the correct thru axle and garmin sensor, but I would like to have power be something more consistent.

Eventually I see myself getting back into tri after 5 years off, but right now I’m focused on the new roadie.

My budget is under $500. Prefer new, but a great quality used device is also an option.

Is 4iiii the way to go?

I only use my 4iiii on my roadie and I’ve not yet used it on the turbo but so far I like it. I had a Avio PowerSense before on the roadie and going by my perception the 4iiii numbers, the Avio was pretty accurate but it wasn’t as responsive or robust as the 4iiii is :+1:

Personally I would avoid one-sided PMs. I did a 2 hour Z2 endurance ride on Monday where my L:R balance was 48:50. I did exactly the same ride this morning (same route, same power within a few watts, same average speed) and my L:R balance was 41:59. With a left-only PM that kind of variation in L:R balance translates to a 14% variation in accuracy, which IMO makes power all but meaningless. SS intervals could actually be suprathreshold intervals.

The rides felt the same, I wasn’t aware of any tightness or weakness in my left leg this morning. If I had to guess I’d put it down to fatigue from doing a 2 hour SS workout yesterday evening. Before I had a dual-sided PM I was never aware of any L:R balance problem (and on plenty of rides there isn’t one). If you’ve got data that gives you confidence that your L:R balance is consistent (e.g. if you regularly train with a Wattbike in the gym or something) than that might be different.

Just gotta track down that last 2% :rofl: :rofl: :rofl:


That’s a wild swing, is it normal for you?

That sounds more like a PM malfunction! I often see my L/R at 53/47, which I thought was at the extreme end of things.

I’ve seen both his numbers but not from the same person unless there was an injury so was curious.

Wouldn’t say normal, somewhere between 44-49% for the left is more common. Think 41% is the lowest I’ve seen (and 51% is the highest) but I’ve seen it a few times. General factors that trend me towards 50:50 include being fresh, working at higher intensity, and having been diligent with single leg and glute activation exercises off the bike. So this morning’s ride was kind of a perfect storm of being tired, riding at low intensity, and having been a bit slack with my routine off the bike in recent months.

Edit: no idea if others see this kind of variation, I guess my point is that it’s not something I was at all aware of previously, and if I had a left-only PM my data would have been all over the place without me realising. Even a modest 3% variation in left leg contribution equates to a 6% variation in accuracy, which is pretty big when it comes to using power for meaningful training

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Ignoring the factor of odd readout, was your power still spot on and felt accurate with your perceived effort? I’m asking because I think I could tolerate that if the reading was consistent to my effort.

What unit do you have? Stages or 4iiii or something else?

as long as you can get the right BB - the Quark should work - I’ve not heard that they are not compatible with Ultegra 11 speed

I would think if anything - the BB might be the issue - but there are tons of adapters - both Trek and Specialized have an SL 6

Do you know what BB standard your Quark is? Which Brand bike do you have?

I don’t see that big a variation no matter what I do from one day to the next. Typically I’m at 49/51 now regardless of the workout although I’ve had 50/50 show up sparingly. Usually it’s a day after a fairly hard workout but not consistently.

A couple years ago it was 52/48 until I started PT for flexibility issues and slowly switched to 48/52 until a couple weeks ago. I felt twisted on the bike and recently learned why it might be, improper pedal stroke habits. Been working on changing it so now I see 49/51 and I’m not feeling twisted as much so hopefully it continues to improve.

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Bike is Specialized Tarmac SL6

I have a Quark GXP 110. I am wondering if I could or should change the chain rings on them. It is currently 50x34 and my current Ultegra is 52x36.

Is it possible to swap out the chainrings from Ultegra to the Quark?

specialized use that OSBB which is essentially a PF30 I believe - you might want to do some checking (I would chat up competitive cyclist) - they also sell a PF30 to GXP adapter from wheels manufacturing for $40.00

no chance that you can interchange Ultegra rings to a Quark - most (newer - last decadish) Ultegra chainrings are 4 spider arm versus 5 - and Shimano have a proprietary shape

You can buy rings for your Quark that would be 52x36 - you would have to make sure your chainring bolt BCD and new rings match - likely your current Quark is a 110 BCD

Based on Specialized’s site, It is showing it is a Shimano Threaded BSA BB.

I know that Quarq currently sells a crankset with 4 spider arms, but you’re right my older version is probably a 5. Too many options and too many oddities to figure out what BB I migh tneed. I just want a good reliable PM that doesn’t cost too much.

But, then again, so does everyone else!

Have you considered going with pedals so you can swap between bikes?

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yeah - I have multiple bikes so I sold my crank based PM and my wheel based PM and got Favero Assioma Pedals. 3 bikes are 10 speed - 1 is 11 speed and I now have a Hammer trainer - The wheel would only fit one bike, and the crank would only fit the tribike, it was a cluster.

they were like $650 but I move them between my bikes - now I have the same power source and cleats for each bike. It removes most of the variables.


Another +1 for a pedal based system.

I have, but I don’t really want to switch pedals, and get new cleats. It is something I am considering. I might actually get a Quarq PM. I have reached out to them. Hoping to get a resolution this week.