DFFT Tires and Wheels 3

Question 1

A driver reports that the steering wheel shimmies (oscillates side to side) at around 45–55 mph but is smooth at other speeds. What is the most likely cause?

Accepted Answer

Static or dynamic wheel imbalance

Answer

Speed-specific shimmy at a narrow speed range is a textbook symptom of wheel imbalance, which creates a resonance at the wheel's natural frequency within that speed band.

Question 2

After replacing a front tire, a technician performs a wheel alignment check. Which alignment angle, if incorrect, would most directly cause rapid tire wear on the inner edge only?

Accepted Answer

Camber

Answer

Camber is the angle of wheel tilt; excessive negative camber places disproportionate load on the inner edge of the tire, causing accelerated inner wear.

Question 3

A vehicle's tires are properly inflated and the tread depth is adequate, but the driver reports poor wet-weather traction. What tire-related fault should be inspected first?

Accepted Answer

Hardened or glazed tread compound from age or heat cycling

Answer

Aged or heat-cycled rubber loses its elasticity and softness, reducing the tire's ability to conform to the road and channel water, significantly impairing wet traction.

Question 4

What would happen if a vehicle is driven with mismatched tires — one radial and one bias-ply — on the same axle?

Accepted Answer

Unpredictable handling and uneven cornering forces due to different flex characteristics

Answer

Radial and bias-ply tires have fundamentally different sidewall and tread flex characteristics, which creates mismatched cornering forces on the same axle, leading to unpredictable and dangerous handling.

Question 5

During a wheel inspection, a technician notices that several lug nuts on a wheel are loose. What is the most serious risk if the vehicle is driven in this condition?

Accepted Answer

The wheel can detach from the vehicle while in motion

Answer

Loose lug nuts allow the wheel to wobble and eventually shear the studs, causing complete wheel separation — a potentially fatal hazard at any speed.

DFFT - Driver Fault Finding Test Practice Test

DFFT - Driver Fault Finding Test Practice Test

DFFT Tires and Wheels 3