When are HitWall and Bump supposed to be called?

I’m trying to make some custom code that will make my pawn bump/slide along a wall instead of getting stuck on it. But HitWall and Bump seem to get called rarely if ever. I set my Pawn’s bDirectHitWall to false, and my PlayerController’s NotifyHitWall and NotifyBump also don’t get called when I run my Pawn into a wall. What do I need to do to make sure that these functions get called?