What size tip do you generally use for a bead border on a three tier cake?

Depends on the cake sizes. But for the most part...a 5. If it's a kids cake where they need to be big, a 7 or 8. I also don't use the same tip for all tiers. I use a smaller beaded border as the tieres get smaller.

I usually use a 5 for cakes as well.

Thank you five it is.