What does SPNSN stand for?

Suspension

The various springs, shock absorbers and linkages used to suspend a vehicle’s frame, body, engine, and drive train above its wheels. A suspension is a mixture between a liquid and fine particles of insoluble solid spread throughout the liquid. A liquid that contains undissolved solid distributed evenly throughout the mixture. A mixture of two substances where small pieces of a solid are suspended in a liquid - for example, milk and orange juice.