Why is the MiG-23 landing gear nontraditional?
This configuration for the main landing gear was necessitated by the fact that the MiG-23/27's narrow fuselage combined with limited internal real estate in that section of the airframe made that type of retraction mechanism the best compromise in terms of fit, weight and providing a wide wheel track for the aircraft to facilitate operations on rough or unpaved airstrips (typical Soviet utilitarian philosophy for going to war).  



An angled MLG strut which retracted forward such as that found on the F-104 or F-16 airplanes was not possible due to the side fuel tanks just aft of the engine inlets.  

Aircraft which have narrow fuselages and high mounted wings are always going to require a more unorthodox retraction configuration for the main landing gear due to space limitations.  Other examples of this include the Dassault Mirage F1, Su-24 Fencer, and SEPECAT Jaguar. 





This placement of the MLG and in this retraction configuration was the best available for the design limits.