petrified wood?
We'd spot one another,
give boosts, or relocate rocks here and there,
ride a small section at a time, the intercoms were very helpful, and we were making progress.
Strangely, at this pace, the trail didn't seem familiar even though I'd ridden it already both ways.
They'd ask: when is the next easier section, and I'd say, "Oh, right around this bend", and then we'd get there and it'd be more misery.