Before driving a CMV ( commercial motor vehicle), a driver must “be satisfied that it is in safe operating condition.” This is the law.
The point of your pre-trip inspection is to examine service brakes, parking brakes, steering mechanism, lighting devices and reflectors, tires, horn, windshield wipers, rear-vision mirrors, and coupling devices where applicable. All of these must be in safe operating order, or you should not sign for an accept a vehicle.
In addition, the vehicle must be one you are certified to drive. [If it is a tractor-trailer, and you were dispatched to pick-up a straight truck and hold a CDL-B license; or if it is a tanker or other vehicle requiring an endorsement you don’t have; notify your dispatcher, and walk away.]
We do not want drivers to perform service that is unlawful or unsafe.
You are much further ahead to say “no” at the onset than to be placed out of service and cited at a roadside inspection later. Be smart. Be safe.