so i crashed my 5inch pretty hard into a concrete wall last week, bent a shaft on motor 2 and cracked the bell slightly. ordered a replacement (same stator size, same kv, different brand because my usual ones were out of stock) and swapped it out last night.

everything spins up fine in betaflight motor test, all four read similar rpms when i push the slider, but when i hold the quad in my hand and spool it up outside it just... feels slightly off. like theres a subtle vibration coming from that arm that wasnt there before. blackbox shows slightly higher noise on that axis too but nothing crazy, like maybe 15-20% more than the others.

i rebalanced the props, checked the screws are tight, even swapped props between arms to rule that out. still the same arm thats buzzy. im wondering if its just the motor internals being slightly different (tolerances, magnet strength etc) or if i maybe bent the arm itself in the crash and didnt notice. arm looks straight to the eye but i havent actually measured it.

anyone dealt with this before? do i just run some RPM filtering and call it a day or should i be more worried about this

honestly the arm is probably tweaked. carbon fiber can look totally fine and still be slightly off ? especially unidirectional layup arms, they dont always show visible cracks when theyre bent. i had the exact same thing after clipping a gate, looked perfect but was like 0.3mm out of true and it drove me insane for weeks before i finally just replaced the arm.

get a straight edge or a caliper and measure tip-to-tip diagonally both ways, if theyre even a millimeter different that could explain what youre feeling. also check the motor mount holes, if the arm took a hit hard enough to bend the shaft the mount threads might be slightly wallowed out and the motor isnt sitting perfectly flat.

different brand motor with same specs on paper doesnt always mean same performance, the stator windings can be wound slightly different, magnet grade varies, even the quality of the bearings out of the box. ive had brand new motors that were just noisy from the factory. id run it for a few packs and see if it smooths out ? sometimes bearings just need to seat in a bit. if the blackbox noise doesnt come down after a few flights then yeah probably look at the arm like the other guy said