Nick_Pyner:
I'm betting you already suspect that the only 55w brake bulbs in the known universe are probably in reply #2, and are quite likely illegal, but you need to be able to handle trailers with more than one standard 6/21w anyway, not to mention heavy vehicles, so the comment about high current is not unreasonable.
Sorry my bad. They are the back up bulbs. I knew there were two of them on at the same time.