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How a Car Works · Chapter 07

Suspension & steering.

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 lets the wheels chase the road while the body sails level above it; steering points the patches where you actually want to go.

· THE SPRING

The spring: let the wheel do the jumping

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 body — comfort lives up herespring — absorbsdamper — calmsthe bump goes into the wheel — not the body

TAKEAWAYThe wheel’s job is to follow the road exactly; the body’s job is to pretend the road is smooth.

· THE DAMPER

A spring must be told to stop

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. The damper is the cure: a piston forced through oil, turning the bounce’s energy into a little heat. One bump, one firm recovery, done.

TAKEAWAYSprings store the bump; dampers spend it as heat — tuning the pair is a whole engineering career.

· THE ROLL

Roll, and the bar that fights it

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. Both wheels rising together — it does nothing. One side compressing alone — it resists, keeping the body flatter without stiffening the straight-line ride.

inside — unloadsoutside — takes the loadanti-roll bar — a spring that only fights leaningcornering force
READThe car so good it was bannedThe Williams FW14B: computer-controlled active suspension at its extreme.

TAKEAWAYThe anti-roll bar resists only when one side moves alone — flat in corners, soft over bumps.

· THE STEERING

Steering: pointing the postcards

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, 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.

TAKEAWAYSelf-centring is geometry, not a spring — your hands ask, the contact patches answer.

FOR THE SELF-CHECK

What to remember

  1. 01The wheel’s job is to follow the road exactly; the body’s job is to pretend the road is smooth.
  2. 02Springs store the bump; dampers spend it as heat — tuning the pair is a whole engineering career.
  3. 03The anti-roll bar resists only when one side moves alone — flat in corners, soft over bumps.
  4. 04Self-centring is geometry, not a spring — your hands ask, the contact patches answer.
NEXT · CH 08Aerodynamics of a carAbove about 100 km/h the air becomes the strongest force on the car — the last chapter is about the fluid the machine swims through.