Following the mediocre test results of the IS-4, as well as the tentative rejection of the IS-5, Soviet tank designers decided to experiment with German design elements in their next heavy tank. The IS-6, while similar to the IS-4 in most respects, had additional angles on the rear of the hull, more severe angles overall, and two main differences in the running gear. The first experiment, Object 252, used large road wheels and eliminated the return rollers. This was similar, not only to the late-war German heavy tanks, but also to the contemporary medium tank T-54. An alternative design was drawn up with a pike nose, but this was never built. The second experiment, Object 253, kept the same type of running gear as on the IS-4, but with a diesel-electric transmission, similar to the petrol-electric drive that the Germans had experimented with on multiple occasions. Without the inconvenience of their factories being bombed, the Soviets believed that they would have more success with this type of drive than the Germans did, but test results were, once again, mediocre.