A method for manufacturing first and second trim parts (3, 21) of a vehicle, the first trim part having a first thickness and the second trim part having a second thickness different from the first thickness, the method comprising the following steps: - adjusting settings of a forming mould to first values; - introducing the first trim part between a front and a back tool (29, 31) of the forming mould, the front tool having a front fixed part and a front movable insert movable with respect to the front fixed part along a main direction, the back tool having a back fixed part and a back movable insert movable with respect to the back fixed part along the main direction; - closing the forming mould by moving the front and back tools (29, 31) toward one another, the first values of the settings being chosen such that, when the forming mould is closed, the front insert has a first front final position along the main direction with respect to the front fixed part and the back insert has a first back final position along the main direction with respect to the back fixed part; - adjusting settings of the forming mould to second values different from the first values; - introducing the second trim part between front and back tools (29, 31) of the forming mould; - closing the forming mould by moving the front and back tools (29, 31) toward one another, the second values of the settings being chosen such that, when the forming mould is closed, the front insert has a second front final position along the main direction with respect to the front fixed part different from the first front final position, and the back insert has a second back final position along the main direction with respect to the back fixed part, different from the first back final position. - adjusting settings of a forming mould to first values; - introducing the first trim part between a front and a back tool (29, 31) of the forming mould, the front tool having a front fixed part and a front movable insert movable with respect to the front fixed part along a main direction, the back tool having a back fixed part and a back movable insert movable with respect to the back fixed part along the main direction; - closing the forming mould by moving the front and back tools (29, 31) toward one another, the first values of the settings being chosen such that, when the forming mould is closed, the front insert has a first front final position along the main direction with respect to the front fixed part and the back insert has a first back final position along the main direction with respect to the back fixed part; - adjusting settings of the forming mould to second values different from the first values; - introducing the second trim part between front and back tools (29, 31) of the forming mould; - closing the forming mould by moving the front and back tools (29, 31) toward one another, the second values of the settings being chosen such that, when the forming mould is closed, the front insert has a second front final position along the main direction with respect to the front fixed part different from the first front final position, and the back insert has a second back final position along the main direction with respect to the back fixed part, different from the first back final position.