Chapter 7 of 8
Chapter 6 ended on a warning: grip only exists while the contact patch is pressed against the road. Roads, unhelpfully, are bumpy — and a wheel that leaves the ground grips nothing at all. Suspension is the system that lets the wheels chase the road while the body sails level above it; steering is the system that points the patches where you actually want to go. Between them they decide whether a car feels planted or nervous.
Bolt the wheels rigidly to the body and every pebble becomes a punch — delivered to the passengers and, worse, to the contact patch, which unloads or leaves the ground entirely with each hit. So each wheel gets a spring: the wheel snaps up and over the bump alone while the body, many times heavier, barely notices. The spring’s stiffness is the car’s character in one number — soft for a limousine that floats, stiff for a sports car that corners flat and tells you everything.
A spring alone has a fatal flaw: it gives back everything it absorbs. Hit one bump and an undamped car pogos down the road for hundreds of metres — early motorists knew the seasick feeling well. The damper (shock absorber) is the cure: a piston forced through oil, turning the bounce’s energy into a little heat. One bump, one firm recovery, done. Tuning the pair — how much spring, how much damping, and different damping for bump and rebound — is a whole engineering career.
Corner hard and the body leans on its outside springs — weight transfers off the inside tyres, and chapter 6 told you what that costs: grip scales with load, and the transfer spends it unevenly. The anti-roll bar is an elegant half-measure: a torsion spring lying across the car, connecting left and right suspension. Both wheels rising together (a speed bump) — it does nothing. One side compressing alone (a corner) — it resists, keeping the body flatter without stiffening the straight-line ride. Formula 1 took this idea to its logical extreme: hydraulics that hold the body perfectly level, computer- controlled, until the rules banned them.
Steering feels like the simplest system in the car — wheel turns, wheels turn — but the geometry underneath is quietly clever. The two front wheels cannot point the same way in a corner: like the differential’s two arcs, the inner wheel needs a tighter angle than the outer, so the linkage is drawn to disagree on purpose. And the steering axis is tilted so the car’s own weight pulls the wheels straight again when you let go — that self-centring you feel leaving a corner is geometry, not a spring. Add the slip angles from chapter 6 and you have the full loop: your hands ask, the patches answer.