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Are they better/worse? I presume they're better because it's more expensive but that's not always a useful metric for being any 'good'.
Would it be more durable or efficient in any measurable way?
hippy-
For applications where there is a force applied perpendicular to the direction of rotation. ie in the direction of the axle left to right.
As far as I understand it -
Would it be more durable or efficient in any measurable way?
In theory at least they will be, yes, because angular bearings are better at taking non-axial loads . In practice I suspect the difference will be marginal if any, and angular bearings will need to have the preload set carefully. Setting the preload on Rotor 3D+ cranks isn't hard or difficult, but it will need to be done right or the angular contact bearings will eat themselves.
PhilDAS
Brommers
The first one has angular contact bearings, the second one doesn't.