MODULE IV

WHEELS AND TYRES

WHEELS

The various requirements of an automobile wheel are

1. It must be strong enough to perform the above functions.

2. It should be balanced both statically as well as dynamically.

3. It should be lightest possible so that the unsprung weight is least.

4. It should be possible to remove or mount the wheel easily.

5. Its material should not weaken with weathering and age. In case, the material is susceptible to corrosion, it must be given suitable protective treatment.

Wheel - Basics

•Most standard wheels are made of steel.

•Some vehicles are fitted with alloy wheels that are made of magnesium or aluminum.

•The rim holds the tyre.

•The well of the wheel allows the tyre to be removed and refitted.

•The centre section is welded to the rim.

•The pilot bore fits to the hub.

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Valve Stems and Cores

– Three functions – It retains the air, it allows inflation and deflation.

•The rubber stem of the valve is pulled into the wheel.

•The valve core contains a spring loaded air valve insert.

•The valve core also has a sealing washer and a seat washer.

•The valve cap keeps out dust and helps keep air in.

Tyre pressures must only be checked and adjusted when the tyre is cold

Wheel Fixings•Wheel studs and nuts attach the wheel to the hub.

•The wheel studs press through the hub or axle flange.

•The taper on the wheel nuts secures and centers the wheel.

•Wheel studs usually have a right-hand thread.

•If it is a left-hand thread, it can be marked with “L”.

•Metric threads can be marked with “M” or METRIC.

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Torque wrench

Wheel Nut Torque

•Correct torque of wheel fixing is vital for all vehicles, and nearly all require the use of a torque wrench.

•Excessive torque can lead to wheel or hub distortion, causing runout and vibration.

•Low torque may allow wheel nuts to work loose and wheels to come off.

•Nuts should be tightened in a diagonal pattern.

Wheel Sizes

WHEEL ASSEMBLY

1. Steel Wheels (Disc wheel)– A very popular design of wheel. Very strong and cheap to produce.

2. Alloy Wheels – Attractive and light weight, but can be difficult to clean.

3. Spoke Wheels (Wire wheels) – Used on older sports vehicles, but cannot be fitted with tubeless tyres.

4. Divided rims – the rims are made in two halves which are bolted together, the rims must never be separated while the tyre is inflated.

5. Split rims – the tyre is held in place by a large circlip, do not remove the tyre unless you have been properly trained.

TYPES OF WHEELS

Custom Wheels

• Several types– Aluminum wheels: cast, forged, or rolled– Race cars: use alloy wheels– Custom wheels for street use: single piece castings

of light alloy aluminum• Wheel offset

• Negative offset: increases track width of tires• Positive offset: found on front-wheel-drive cars

TYPES OF WHEELS

1. WIRE WHEEL2. DISC WHEEL

Wire wheel (or)

DISC WHEEL