A leaf spring is commonly used for the suspension in vehicles. It transmits force from the wheels on the bogie frame and the body. It prevents the variations in the road surface encountered by the wheels from being transmitted to the vehicle body.

How to Get Leaf Spring
Leaf Spring is a starting element.

Leaf Spring Doodle Tanks Combo
+Four-Cylinder = Infantry Tank Hull
+Infantry Tank Hull = Christie
+Infantry Tank Hull = Morozov
+BT-2 = Endurance