Complex sentence: The plane's undercarriage was a traditional tricycle type with a twin wheeled nose gear, and with each of the two six-wheeled main legs utilizing the same tires used on the Douglas DC-8, but filled with nitrogen and at lower pressures.
Split into simpler sentences: The plane's undercarriage was a traditional tricycle type with a twin-wheeled nose gear. Each of the two six-wheeled main gear utilized the same tires used on the Douglas DC-8, but which were filled with nitrogen and to lower pressures.