# SUSPENSION SYSTEM FOR AN ALL TERRAIN VEHICLE PART 2

2. CALCULATIONS
Total sprung mass: The entire mass that acts upon the wheels of the vehicle is considered as
sprung mass i.e weight of the roll cage ,driver, engine, cvt, steering wheel, steering rack,
braking. The lower the sprung mass is the better the performance of the vehicle.
Sprung mass:175 kgs
Total unsprung mass: The mass excluding the sprung mass is considered as unsprung mass
i,e weight of the wheels, uprights, knuckles, a arms, Hubs, shock absorbers, trailing arms.
Unsprung mass: 65 kgs
Total weight: sprung mass + unsprung mass gives the total weight of the vehicle
Total weight:175 +65 = 240kgs
Kerb weight: The weight of the vehicle excluding the driver’s weight
(Also known as curb weight)
Kerb weight : 240 – 60 = 180kgs
(Drivers weight is considered as 60kgs)
Front track width: Front Track width is the distance from tire centre to the other tire center.
There is no specific formulation in deciding the track width of the vehicle but we need to
consider certain basics like[1]
1) up to what value the rules will allow ?
2) what is the predominant track type the on which vehicle is to be run?
3) Are low speed tight circuits are of concerns ?
4) Is top speed thus top frontal area is important ?
Front track width: 52’’inches
Rear trackwidth: selection criteria for rear track width depends upon the same
considerations as of front. However, we preferred the rear track width to be slightly greater
than front for more stability of the vehicle
Rear track width :53’’inches
Static Ride height: static ride height is also said to be ground clearance. It is nothing but the
distance between the ground to the chassis lowest point . It is always desirable to maintain a
ride height at a moderate height which is not too high and not too low because if the ride
height is low the vehicle may get hit at the bottom during getting over a bump and if the ride
height is very high the height of COG increase which is also not a desirable scenario. So by
benchmarking the ride heights of different commercial ATV’s the ride height for our vehicle
is determined as
Static ride height :12’’inches
Tire diameter: The selection criteria for the diameter of the tire depends upon 2 factors
1) Vehicle torque
2) Braking disc and caliper that gets fitted inside rim
Tire diameter: 23”inch
Wheel travel: The movement of the wheel in vertical direction from top to bottom is known
as wheel travel.