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What is the cheapest and easiest way to add a power meter to my Diamondback Haanjo 4? It has a Praxis M30 BB and a Praxis Alba crankset. Thanks!

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I was going to say that you should send the left crank arm into 4iiii to install the strain gauges. They charge US $300.

However, I checked, and they do not list the Alba as eligible for this service. The reason likely has to do with economics. All power meters use strain gauges to determine how much you are flexing the crank arm (it’s more complicated than that because the gauges need to isolate the amount of flex in one dimension, but bear with me). Beyond that, however, a power meter company needs to determine how much the crank deflects under a set amount of torque. All cranksets have different wall thicknesses and materials, so all will deflect a different amount for the same amount of force. In theory, I see no reason the Albas can't take strain gauges. However, they're entry-level cranks. If you could convince 4iiii or Stages to do the calibrations, you could get either company to do the factory install, but they are likely to judge that the demand for Albas with power meters is too small.

Shimano 105 through Dura Ace cranks are all very common, so it’s clearly worth it for power meter manufacturers to validate their meters on all those cranksets. Campagnolo is a much less frequent groupset choice, so companies may only support some models, e.g. 4iiii only supports Potenza, Record, and Super Record, leaving Chorus, Centaur, and everything below out.

Praxis is a much smaller brand. 4iiii supports the carbon Zayante cranks, but not the Albas. Stages doesn’t support them at all. Pioneer, while they sold power meters, only supported Shimano cranks.

There are some options. I believe that some versions of the Alba have removable spiders, and Power2Max should make a spider-based power meter compatible with this crankset. You could buy a Zayante crankset with a power meter pre installed. Especially if you already use Look road pedals, you could buy pedal-based power meters instead; of the available ones, the Favero Assioma appears the cheapest and it is also very well-regraded. All these come in cheaper single sided variants as well as dual sided.

Sadly, you will need to change your bottom bracket to use Shimano cranks or a BB30 crank with power to your bike. The M30 Bottom bracket has a 30mm spindle that tapers to 28mm on the non-drive side, whereas BB30 is 30mm throughout, and Shimano is 24mm throughout. Changing the bottom bracket would make switching cranks more expensive.

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    Sadly, I believe you can’t retrofit Shimano cranks or a BB30 crank with power to your bike. Sure you can - if you also replace the bottom bracket. Assuming it's a BB30 or PF30 frame, there are probably more than a few options available in order to use a standard Shimano or BB30 crankset. – Andrew Henle Jun 2 at 0:36
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    @AndrewHenle what I should have written was that replacing the BB will raise the cost. It’s not clear if the net cost will be lower than a single-sided pedal solution or the Power2max spider – Weiwen Ng Jun 2 at 1:27
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    What about a (single-sided) pedal based powermeter? – Carel Jun 2 at 7:53
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    Pedal based powermeters are only a solution if you use road-cleated pedals, of course! – Carel Jun 2 at 8:13
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    Why is it neceaaary to get an Alba crank powermeter? Can be any left crank compatible with the interface and of the same length as the right one. – Vladimir F Jun 2 at 15:01
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Pedal-based power meters are the absolute easiest to install. The calibration procedure is also the simplest in their case. This makes them also the easiest to move between bikes.

The cheapest pedal power meter, single-sided Favero Assioma Uno can be had for €445 (October 2020), so it's a bit more expensive than the cheapest single-sided crank-based power meters, but the ease of installation makes up for the difference in my opinion. The more immediate problem is that the company is backlogged and the shipping times are currently 2 months or more in 2020.

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  • What you write is true, but note that the bicycle specified in the original question is a gravel bike, and the Favero Assioma is based on Look road cleats (as are all the current pedal power meters save for SRM's very expensive SPD-compatible X-Power meter, which I think has been officially released, although it's listed as coming soon on SRM's site and out of stock elsewhere). You can certainly run road cleats and shoes on gravel if you know you won't walk much (and many of us actually won't be walking much). – Weiwen Ng Oct 19 at 15:36

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