WHY REAR WHEELS IN AUTO-RICKSHAW ARE TILTED OUTWARDS ??

You might have seen that rear wheels of auto rickshaw are tilted outside.What is the purpose of this?Does it not lead to tyre wear?We will all discuss about this here.

First of all we should learn about an amazing concept which is known as "Camber angle." 

Camber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear.If the top of the wheel is farther out than the bottom (that is, away from the axle), it is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber.So,in case of three wheeler we have positive camber.

Now let us understand why this positive camber is provided in auto rickshaws.
A three wheeler or what we call as auto rickshaw  generally transports a whole lot of passengers.(at least 6 passengers in the passenger bay) in a single trip. That is approximately 360 kg(considering each passenger's mass to be 60 kg). In figure above if you see the image depicting positive camber,you will notice that the tire contact patch is more towards the region near the outside tire wall. This is the scenario when the rickshaw is in unloaded condition. 

Now when the rickshaw gets loaded , the normal force due to the weight of the passengers causes an anticlockwise moment on the axle supporting the wheels, making the wheels to attain neutral or no camber condition. Thus when the vehicle is loaded there is greater contact patch thus better traction.

If the wheels had the neutral camber in the static unloaded condition, during the loaded scenario the wheels will reach the negative camber alignment resulting in reduced contact patch and uneven tire wear(near the inside tire wall).