It has often been said that the Pacers are of poor quality. Instead of the usual bogies, Pacers use a basic four-wheel two-axle underframe. This often makes for a ride that is noisier and less comfortable than other trains, especially over points, and a loud squealing noise is heard around tight curves. Not having bogies also makes for a worse suspension and a bumpier ride; Pacers have been nicknamed "nodding donkeys" because of the trains' up-and-down motion on uneven track. The basic bench seating can also be uncomfortable. The early units, especially the s, were also very unreliable.