An axlebox assembly having at least one rolling bearing designed to be mounted on an axle, and a cover designed to be fastened with the axle such as to axially maintain the at least one rolling bearing between the cover and an abutment of the axle is provided. A backing ring is mounted on the axle between the at least one rolling bearing and the abutment. The backing ring includes a deformable portion so as to substantially fit the shape of the abutment of the axle.