I've heard that the 30A's are, but it's a massive safety net if you're new to roboteering I suppose - that was my reasoning for going for the 85A's instead of the 30's. Might be a bit more cash, but if you somehow manage to pull more than 30A by wiring something up wrong or stalling a motor, it's definitely better to not lose an ESC! That, and you're set if you ever choose a much beefier drivetrain that draws a lot more amps.