A driver inspects a car tyre and records tread depth readings across different sections of… — UK Driving Theory Test

A driver inspects a car tyre and records tread depth readings across different sections of the tyre: $2.2\text{ mm}$ on the outer shoulder, $1.4\text{ mm}$ across the central three-quarters of the tyre's breadth, and $2.0\text{ mm}$ on the inner shoulder, measured continuously around the entire outer circumference. Which of the following correctly describes the legal status of this tyre and the underlying maintenance issue indicated by this wear pattern?

A
The tyre is legal because the average tread depth across the full breadth exceeds $1.6\text{ mm}$ , and the wear pattern indicates normal, balanced tyre pressure.
The tyre is illegal because the tread depth in the central three-quarters is below $1.6\text{ mm}$ , and the wear pattern indicates the tyre has been operating over-inflated.Cevap
C
The tyre is illegal because UK law requires at least $2.5\text{ mm}$ of tread across the entire breadth, and the wear pattern indicates the tyre has been operating under-inflated.
D
The tyre is legal as long as the outer shoulders remain above $1.0\text{ mm}$ , and the wear pattern indicates misaligned front-wheel tracking.

Cevap

The tyre is illegal because the tread depth in the central three-quarters is below

1.6\text{ mm}

, and the wear pattern indicates the tyre has been operating over-inflated.

Under UK law, car tyres must have a minimum tread depth of at least

1.6\text{ mm}

throughout a continuous band comprising the central three-quarters of the breadth of the tread and around the entire outer circumference. Because the central band measures only

1.4\text{ mm}

, the tyre is illegal. Furthermore, excessive wear focused along the middle of the tyre tread is the classic diagnostic indicator of continuous over-inflation.

Adım Adım Çözüm

Evaluate the measured tread depth against UK statutory requirements.

The central three-quarters of the tyre measures

1.4\text{ mm}

, which is below the mandatory UK minimum threshold of

1.6\text{ mm}

UK law mandates that passenger car tyres must maintain at least

1.6\text{ mm}

of tread across the central three-quarters of the tyre's breadth and around its entire outer circumference.

Analyze the physical wear distribution across the tyre profile.

The tyre exhibits significantly higher wear in the centre (

1.4\text{ mm}

) compared to the shoulders (

2.0\text{ mm}

and

2.2\text{ mm}

When a tyre is over-inflated, the centre of the contact patch bulges outward and bears the majority of the vehicle's load, causing rapid wear along the centreline.

Synthesize the legal finding and the mechanical cause.

The tyre fails legal safety standards and must be replaced, and the driver must reduce inflation pressure to the manufacturer's recommended cold specification.

Driving on illegal tyres carries penalty points and fines, and over-inflation compromises vehicle grip and braking efficiency.

Anahtar Kavram

UK legal minimum tyre tread depth (

1.6\text{ mm}

across the central three-quarters and entire outer circumference) and tyre wear pattern diagnostics.

Tahmini Süre:1m 15s

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

Sık Yapılan Hatalar

Konular

Bu konudan daha fazla soru