A bicycle crank assembly with adjustment orientation system for ovoid toothed chain rings, comprising: - a shaft comprising a first end portion, a second end portion, and a central body located between the first and second end portions, said central body arranged to be rotatably supported in a bottom bracket in a bicycle frame; wherein said central body, in a n adjacent portion to the first end portion, comprises a projecting member that extends radially outwardly; wherein said first end portion, in an axially adjacent portion to said projecting member, comprises a first torque transmission profile; wherein said first end portion further comprises a second torque transmission profile; and wherein said second end portion comprises a third torque transmitting profile; - a transmission element, for incorporating at least one toothed chainring for driving a chain, comprising a first coupling portion including a first opening provided with a fourth transmission profile to non-rotatably engage with the first torque transmission profile of the shaft; - a right crank corresponding to a drive side comprising at one end a second coupling portion provided with a fifth torque transmission profile which is non-rotatably engaged with the second torque transmitting profile of the shaft; - a left crank corresponding to the non-drive side, comprising at one end a third coupling portion provided with a sixth torque transmission profile which is non-rotatably engaged with the third torque transmitting profile of the shaft; wherein the first, second, third, fourth, fifth and sixth torque transmission profiles (120, 121, 141, 301, 211, 411) are geometrically configured as patterns circularly and outwardly arranged and coaxial with a rotation axis of the shaft which is also coincident with a rotation axis of both the right and left crank and also with a rotation axis of the transmission element; wherein the first and fourth torque transmission profiles (120, 301) when engaging define, in a coupling position between the transmission element and the shaft, N1 angular positions equally spaced along 360°; wherein the second and fifth torque transmission profiles (121, 211) when engaging define, in the coupling position between the right crank and the shaft, N2 angular positions equally spaced along the 360°; wherein the third and sixth torque transmission profiles (141, 411) when engaging define, in the coupling position between the left crank and the shaft, N2 angular positions equally spaced along the 360°; wherein combining the N2 angular positions provided by the coupling between the right crank and the shaft with the N1 angular positions provided by the coupling between the transmission element and the shaft, Nt relative angular positions between the right crank and the transmission element are obtained, being the Nt value the least common multiple of the N1 angular positions and the N2 angular positions; wherein said Nt value is greater than or equal to 45; characterized in that the bicycle crank assembly comprises primary marks arranged on the shaft, secondary marks arranged on the transmission element, and reference marks also arranged on the transmission element, so when combining the secondary marks and the reference marks, an angular graduation system is generated, allowing the user to define a desired angular orientation (cp) firstly aligning the secondary marks with the primary marks corresponding to the desired orientation by engaging the first torque transmission profile with the fourth torque transmission profile in the corresponding position, and secondly aligning the direction of the longitudinal axis of the right crank with the reference marks by engaging the fifth torque transmission profile with the second torque transmission profile. - a shaft comprising a first end portion, a second end portion, and a central body located between the first and second end portions, said central body arranged to be rotatably supported in a bottom bracket in a bicycle frame; wherein said central body, in a n adjacent portion to the first end portion, comprises a projecting member that extends radially outwardly; wherein said first end portion, in an axially adjacent portion to said projecting member, comprises a first torque transmission profile; wherein said first end portion further comprises a second torque transmission profile; and wherein said second end portion comprises a third torque transmitting profile; - a transmission element, for incorporating at least one toothed chainring for driving a chain, comprising a first coupling portion including a first opening provided with a fourth transmission profile to non-rotatably engage with the first torque transmission profile of the shaft; - a right crank corresponding to a drive side comprising at one end a second coupling portion provided with a fifth torque transmission profile which is non-rotatably engaged with the second torque transmitting profile of the shaft; - a left crank corresponding to the non-drive side, comprising at one end a third coupling portion provided with a sixth torque transmission profile which is non-rotatably engaged with the third torque transmitting profile of the shaft;