Originally Posted by
arex
I'm a bit heavier than you, and I've yet to break something on a Brooks. Also, using a suspension seatpost would, I'd think, soak up a lot of the stress of your weight on the saddle. I'm guessing it was just a defective rail.
I’m thinking the suspension adds sinusoidal load cycles to the seat rails. Think of amplitude of waves and those peaks strains add up over so many cycles. Even tho the rails are steel, they will eventually fail after so many cycles.