Bringing a classic car back to a condition where it will be classed as roadworthy by the relevant authorities is a responsibility that cannot be taken lightly. Attending to the underbody of the vehicle- in particular its brakes, suspension and steering should always be a major priority.
The first stage in any road test is to try the brakes. The car should stop smoothly with no fading (diminishing of stopping power), and it should track in a straight line.
A grinding or scraping noise indicates that the brakes may be worn down past the linings and will need to be replaced.
If the car pulls to one side when braking, or the brake pedal goes down slowly, the hydraulic system may be leaking.
An almost certian way to test if brake fluid is leeking to check the examine of each wheel , as well as around the master cylinder.
Next step in a pre-purchase check is to test the steering, preferably under a few different conditions. If the steering wheel starts to shudder or wander at certain speeds, means that the front end may need a rebuild.
If the vehicle has been standing for many years, the restorer can assume that a major overhaul to all the underbody systems is on the cards, a factor that must be taken into account in the seller's asking price.
It is a fact that while most amateur mechanics will know their way around an engine, a lot fewer will possess the necessary knowledge and experience to work on a vehicle's underbody- a task that carries a lot of responsibility in ensuring driver and passenger safety as well as their comfort.
Costs of these parts are usually low, while quality is fairly high. The same procedures apply to the vehicle's shock absorbers. Going back to the pre-war years, hydraulic type shock absorbers were popular and remained so until the Sixties. It was then that they were replaced by telescopic shock absorbers which are popular today. When a vehicle's wheel goes over a bump in the road, the suspension spring allows for an according adjustment allowing the vehicle floor to remain level. The suspension spring provides essential movement for the wheels while the shock absorber act as a form of vibration damper for the spring. Hardly any system connects the driver so directly to his or her car than its steering. A variety of mechanical solutions exist to make the car change direction as the driver wishes. Nearly all common types of steering follow the so-called 'Ackermann' principle, developed by the renowned German of hat same name more than two hundred years ago. The revolutionary principle behind the Ackermann theory is that the axle itself does not turn, the front wheels instead. Simple though they may appear, springs pay a considerable influence on a car's handling characteristics. With no springs to support the car’s suspension, the hard jolts which are felt when driving over potholes or bumps in the road would be transmitted directly to the chassis frame or body, placing an undesirable load on them. The stiffness of the springs, the so-called spring rate, is defined as the relationship between the spring travel and the load imposed on them. The spring rate depends on the material used to produce the springs (we'll limit ourselves to steel springs in this instance), on its specific qualities such as the quality of the steel and size and shape of the springs. These specific qualities will allow the springs to absorb the forces exerted on them as they become compressed.
Changing brake pads
Restoring rear axles