A non-steerable lift axle that is not raised when turning, especially in a tight corner, will scrub concrete and impose high lateral stress on the wheels and chassis components of your vehicle. Raising the fixed axle when cornering will help decrease tire wear, reduce maintenance costs, and ensure proper functionality of the auxiliary lift axle when in use.
It is also important to be aware of the regulations within the states that your vehicle will operate in. Some state authorities prefer the auxiliary lift axles stay lowered and in operation when turning or that the auxiliary controls remain outside of the vehicle's cab. In these cases, it may be best to specify a steerable auxiliary lift axle for your vehicle.