Suspension Systems Questions and Answers

Answer: A

A stiff bush locates the arm precisely and improves the response, but it transmits road noise and impact harshness into the body. Hydraulic bushes attempt to give both by being stiff to slow movements and compliant to rapid ones. The order in which the effects act is what decides the outcome, so it is worth establishing first. Most errors here come from carrying across a result from a neighbouring case where it does not hold. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.

Answer: B

A hydraulic bush contains fluid in chambers connected by a track, so it behaves as a damper as well as a spring and its stiffness depends upon frequency. It gives precise control with good isolation. Polyurethane is simply stiffer at every frequency. Checking which component actually carries the load settles most questions of this kind at once. Naming what changes and what stays the same is the reliable route through questions of this shape. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: C

Wear allows the arm to move within the bush, which knocks over bumps and lets the geometry wander under load. A rumble that varies with cornering points to a wheel bearing. Levering the arm reveals the movement. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: D

Hydrolastic and hydragas systems connect front and rear units on each side so a bump at one wheel raises the other, reducing pitch. Citroen hydropneumatic systems use a pump and spheres to give levelling as well. Both reduce the pitching motion. The shared behaviour explains why these belong together and the differences explain why both exist. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. The quantity that varies and the quantity that does not are worth naming before any substitution is attempted.

Answer: A

Connecting the front and rear units on one side means a bump at the front partly raises the rear, so the body translates rather than pitching. Side to side connection would reduce roll but is undesirable. The distinction is the whole point of the layout. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. The order in which the effects act is what decides the outcome, so it is worth establishing first.

Answer: B

Semi-active dampers alter their valving continuously but can only dissipate energy, whereas a fully active system supplies it. Magnetorheological fluids are one implementation. Fully active systems are rare because of their power consumption. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Checking which component actually carries the load settles most questions of this kind at once. Checking the units of each quantity catches a wrong formula before the arithmetic begins.

Answer: C

Iron particles suspended in oil align in a magnetic field and thicken the fluid within milliseconds, which allows the damping to be varied without valves. Electrorheological fluids respond to an electric field instead, so the last option confuses the two. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Tracing the requirement back to the physical constraint that produces it makes the answer follow. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: D

Changing the current changes the damping in about a millisecond, far faster than a solenoid valve can move. That speed allows individual wheel control over each bump. The fluid and the electronics both make it expensive. Naming what changes and what stays the same is the reliable route through questions of this shape. The shared behaviour explains why these belong together and the differences explain why both exist. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: A

A van may double its weight between empty and laden, so a single rate cannot suit both and a helper spring or a progressive rate is used. Air suspension solves it completely by adjusting the pressure. A soft spring alone bottoms out when laden. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: B

A second shorter spring above the main one contacts its stops only when the deflection is large, so the rate rises with load. More leaves simply stiffen it throughout. Tapered single leaf springs achieve a similar effect by their shape. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.