It is true that some Ford Mustangs have independent rear suspensions (IRS), while others do not. Yet whether the rear suspension is independent or not is not necessarily why Ford Mustangs seem to spin out so frequently, though solid rear axles do tend to have a slightly harder time cornering than independent ones. One of the major reasons why Mustangs have not had independent rear suspensions until recently has lots to do with the cost of a solid axle compared to an IRS setup. Keep in mind that the original 1965 Ford Mustang was a car that promised great performance and an impressive top speed, but at an affordable price. The solid rear axle was chosen, and the rest was history — at least until 2015 rolled around.