Chitina - McCarthy/Kennicott road is an old railbed from the 1920's. It has all the pitfalls of that era (i.e. not primarily designed for wheeled vehicles) plus the assorted debris of construction of the McCarthy / Kennicott /Mines area plus the assorted debris of the exodus of the McCarthy/Kennicott /Mines area in the late '30's plus the assorted debris of the intervening 80 years (all in round numbers).
In summer, IMNSHO, as noted, it's best to travel long after or just before a grading to avoid freshly turned up debris. In Winter, better to travel just after a grading. It's been a while, but on one of my early trips, I made a point of looking for spikes.....was able to pickup 10 - 12 of them before McCarthy.