Our pucks are made of fiber reinforced nylon and have been thoroughly abused and tested to meet the demands of the roughest trails and the heaviest loads. We always turn to trail builders to test our racks’ durability because if anyone can break a bike part and load far more than is advised on a bike it’s trail builders.
Additionally, the upper attachment uses the pucks only to prevent the rack from rotating around the axle. The vast majority of the weight is carried on the axle.