Acctually there is no rule that the eldest should be chief. It just seems that way because Cutter chose Ember over Suntop. He only did that because Ember has more wolf blood then Suntop and that would be kind of going against the way, to put an immortal in as chief.
Think about it. Timmorn chose Rahnee as the next chief and her sister Laststar was older, not to mention all the other children he had. He just felt Rahnee was the best choice. She was his favorite of his children.
And after Rahnee, there was no chosen succesor. She had a lot of children, and Pre-Pacer was the best choice to be the next chief. Now when it comes to Skyfire and Two-Spear, there are a few reasons most of the elves wanted Skyfire over her brother. The main reason is because HE was crazy, the second reason is because he wasn't born of recognition, which to the elves is a very seriouse thing.
Like to us humans, in many cultures if you are born to a mistress, or out of wedlock, you have no rights to the family "stuff", whereas the children born to the married couple get everything. A child born of recognition was ment to be, a child born outside of recognition wasn't. That's how the elves think. I am not saying that an elf child born outside of recognition wouldn't be loved just as much, just that in the Wolfriders case, it's a chain of comand, and a child born of recognition by deffinition is stronger and have more of a chance to be gifted (as in healer or rock shaper or Treeshaper). Therefor, It is not the oldest that is supposed to be chief, but the strongest and best suited for the job - hence Skyfire over Two-Spear.
Another example of the oldest not being chosen is of Tanner. He had two older brothers and I believe a sister, Yet he was chosen to be chief. That is why challenges are taken so seriously in the Wolfrider tribe. To take the leadership away from the weak. Which hasn't really happened (off the top of my head) except for the case of Scouter taking it away from Ember. But, She (of the chief's Line) won it back. Oh, I'm sorry, it did happen once. Ice, or Wolfrider as he liked to be called, challenged Rahnee She-Wolf and won, but the tribe split, and his half ended up dead because of his arrogence. Leaving Rahnee (of the chief's Line) in charge again. And when it comes to Ember wanting to recognize first, maybe she just wants to keep to the way, and have her child of recognition go after her like all the rest of the chiefs did. You have to remember, Tier is decended from the Go-Backs. They could care less about recognition. She just wants to fallow the way.