A method to modify the geometry of a connecting rod of an internal combustion engine, the method comprising: providing a connecting rod comprising a crankshaft bore at a first end, wherein the first end comprises a bearing cap (15, 12C) and a bottom end portion of the connecting rod; mating the bearing cap (15, 12C) with the bottom end portion of the connecting rod at a mating surface to form the crankshaft bore of the connecting rod between the bearing cap (15, 12C) and the bottom end portion; the method being characterized in that the bearing cap (15, 12C) and the bottom end portion both comprise a width upset portion (20R, 20C) in the vicinity of the mating surface, so that both the bearing cap (15, 12C) and bottom end portion have a locally wider size, in a width direction which extends perpendicular to both a link center line connecting both centers of a small portion and a large portion of the connecting rod and an axial direction of a crankpin of the crankshaft, at their width upset portion (20R, 20C); the method further comprising: machining the width upset portion of the bottom end portion to reduce a width of the bottom end portion of the connecting rod; machining the width upset portion of the bearing cap (15, 12C) to reduce the width of an upper part of the bearing cap (15, 12C) next to the mating surface; reducing the width of the bottom end portion of the connecting rod and the width of the upper part of the bearing cap (15, 12C) to a width smaller than the width of a lower part of the bearing cap (15, 12c) and smaller than a cylinder bore of the internal combustion engine, wherein the width upset portion of the bottom end portion of the connecting rod and the width upset portion of the bearing cap (15, 12C) are machined together while fastened together by bolts such that the width of the bottom end portion of the connecting rod and the width of the bearing cap (15, 12C) at the mating surface are identical. providing a connecting rod comprising a crankshaft bore at a first end, wherein the first end comprises a bearing cap (15, 12C) and a bottom end portion of the connecting rod; mating the bearing cap (15, 12C) with the bottom end portion of the connecting rod at a mating surface to form the crankshaft bore of the connecting rod between the bearing cap (15, 12C) and the bottom end portion; machining the width upset portion of the bottom end portion to reduce a width of the bottom end portion of the connecting rod; machining the width upset portion of the bearing cap (15, 12C) to reduce the width of an upper part of the bearing cap (15, 12C) next to the mating surface; reducing the width of the bottom end portion of the connecting rod and the width of the upper part of the bearing cap (15, 12C) to a width smaller than the width of a lower part of the bearing cap (15, 12c) and smaller than a cylinder bore of the internal combustion engine, wherein the width upset portion of the bottom end portion of the connecting rod and the width upset portion of the bearing cap (15, 12C) are machined together while fastened together by bolts such that the width of the bottom end portion of the connecting rod and the width of the bearing cap (15, 12C) at the mating surface are identical.