[ProfessorCook]

I'd still use the sealant. it'll make things messier inside, but it should seal that crack. (In fact, you could probably get away with that fix for a very long time.)

 

[ProfessorCook]

If there's no visible damage to the rim, but a crack in the rim body, you've got a good argument that this is the result of a manufacturer's defect. If the crack was on the edge of the rim, not so much.