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Discussion Starter #1
My bike came with NX cranks and in the last two decades worth of bikes these are the first that are notably bad. While seated I can observe nearly 1cm of flex with only slight ankle rotation and this gives me the fear. Normally I’d just slap XTs on there and be happy, but it seems like there are chainring failures with the 12 speed stuff? Seems like Shimano qc isn’t what it used to be? I do like the steel Eagle chainrings that are 15 bucks, perhaps the only thing I like about my current setup for the economics and durability. So I’m considering GX cranks as a replacement. Do these have any flex issues or notable shortcomings?
 

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NX and GX cranks are quite similar, 1cm flex is a LOT! Are you sure there is a 1 cm flex in the crank arm?
 

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Discussion Starter #3
Yeah, when I rotate my heel outward and the cranks are at 3/9 o'clock, it's pretty obvious, but also happens at 12/6 when applying downward pressure. My understanding is that NX are 6000-series versus 7000-series alloy on the GX. It also looks like there is substantially more material halfway between the pedals and bb:
1912675
 

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2020 Specialized Rockhopper Expert 1x / 2010 Specialized Hardrock Disc
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Yes you are correct the GX uses higher quality aluminum stronger/lighter. I have the new version of the GX Eagle crankset & I love it. Not sure if the NX has issues, or this is an installation problem. The GX does have better manufacturing and better tolerances in production, but 1cm sounds an awful lot. I would double check the install and spacer setup. Each setup calls for different spacers on either side. Sometimes in the BB and almost always between the cranks and bb. There is also a preload adjuster knob that is a quarter or an eighth of a turn one way or the other goes from perfect preload to not enough or too much. Very fine tuned preload adjustment is needed to hit the sweet spot.
 

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Discussion Starter #5
Well if anything there's too much preload, certainly no slop or play that I can detect. It's definitely the arm itself bending. I'll send along a video after the kid's asleep.
 
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