The work concerns the diagnostic assessment of the technical condition of the car suspension. The paper discusses practical problems that usually appear during testing of car shock absorbers mounted in a vehicle. The results of experimental tests for passenger car, carried out according to the EUSAMA standard test, were compared with the results obtained using newer methods (phase angle method and half power bandwidth method – HPBM). The article also deals with the issue of incompatibility of typical excitation at diagnostic devices for testing suspension with the one that often occurs in road conditions (by simulation method). The main purpose of the work was to assess the usefulness and reliability of various diagnostic methods intended for the testing of vehicle shock absorbers without disassembly them from the vehicle. The analyses carried out indicated the advantages and disadvantages of these methods in practice. It is also shown that the conditions of diagnostic tests correspond poorly to the operating conditions of the shock absorbers under normal vehicle operating conditions. An important factor in this case is the sliding friction in the suspension.