Apologies in advance if this is already widely available knowledge, but this is new to me.
I’ve always understood to install the bearings with the correct side in. After reading dozens of posts on changing wheel bearings over the past couple months, only now have I come across this knowledge.
I’ve put three new bearings on my right rear axle, not knowing how easy this is to check for. I’m about to change bearings for the fourth time in the span of mere weeks. Trust me, you don’t want to do this more than once if you don’t have to.
Check for the ABS encoder with something a magnet will pull easily, like a paper clip or razor blade, and install the bearing that side in.
This video explains how common the problem is, and how simply to avoid it before you put useless bearings in.