Hi Carbon_Dude. Yes I know the forks are designed for 160mm and you need the spacer to get to 203mm which I am already using. But given that, why have niner then put on a limit of 185mm? Are the 203mm too powerful for the forks? Or is there another reason?
Possibly Niner wants to limit the torque load on the fork to what a 180mm rotor can impart to the leg of the fork. Having the larger 203mm rotor may have contributed to your initial failure.
I'm thinking it was a contributing factor as well - Niner forks are built sturdy as hell, I know several guys who have them and they all say the same thing - STIFF. If Niner is limiting rotor to 185mm on that fork, and you're a big guy adding 10% more braking force higher up on a Chinese fork, that might be an issue.
As a point of reference, I'm 6'3" and 220, more with riding gear and such, and I ran 203mm on my Rumblefish for a while, with a 185mm rear. After a while, I switched back to 185/160 (what came from the factory) and didn't notice any lack of stopping power. While the 203mm has numerically increased stopping power, it's not massively different, and I've had zero complaints about a 180/185mm front - and I never use more than one finger for braking. Pretty sure I could survive a 160/160 setup if I wanted to get weight weenie, which... yeah, no.
Without a maximum rotor size specified, it's not something you could have known unless you saw it elsewhere and knew to ask the question - so hopefully they'll still help you out, but you might wanna step down that rotor size at least one step.
