Friday , 21 September 2018
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Wheels on a car go round…

Kedar Kulkarni

“What is wheel alignment and how often do we need align wheels?” asked Raju.   

Balancing tyres helps prevent a bumpy drive which is caused due to uneven weight distribution said Raju’s father. He then asked: “Do you know how the car is connected to the wheels on which it moves?”

Raju said it was through suspension. His father replied that the four wheels must be aligned properly so that the car moves well and there is uniform wear of tyres. The pair of wheels on the left and right should be parallel and the rear and front pair must be in one axis which means their centres must be aligned. This will ensure that the car moves without dragging on one side, responds well while turning and the tyres do not wear fast.

In simple words there are three elementary angles which are checked when the alignment is done on computerised fixtures.

The camber is the angle at which the wheels are inclined as seen from front of the vehicle. If the bottom of the wheels are closer than the top then it is positive camber, the opposite of which is called negative camber.

The toe is at an inward or outward angle when viewed from top of the vehicle. If the front part of the wheel is inwards and the diametrically opposite end is outward it is called as toe in, it opposite is toe out.

The caster angle is the angle which the suspension makes with the axis of the wheels. If the point at which the suspension is fixed is in front of the axis then it is called negative caster and if it is behind the axis of the wheels it is called positive caster. Most cars have positive caster.

The caster angle isn’t normally adjusted except in cases wherein there has been an accident with suspension damages.

“If there is a problem with the camber or toe angle there will be remarkable wear on tyre. If it is positive camber then the tyres will wear on the outside and negative camber will lead to wear on the inside. Similarly toe in and out will impact the wear on tyres and also ability to keep straight line while driving. It will also cause problems while turning. When abnormal pattern of wear is seen on tyres or if the car is dragging on one side it is time to check the wheel alignment. It is generally recommended to check the alignment after approximately 5000 kilometres.

(Writer is a mechanical engineer and runs a hands-on science activity center at Margao)

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