Spoilers for Honda Civic EG

A rear spoiler sits on the boot lid, tailgate or roof edge and changes how air leaves the back of the car. It can reduce rear lift and tidy the wake, and it gives the tail a sportier outline. The spoilers here are mostly listed by model, in polyester, ABS or carbon, and one has a built-in brake light.

Air flowing over the roof and down the rear screen eventually breaks away from the body and leaves a turbulent wake. On a saloon, a lip on the boot lid slows the air just ahead of it, raising the pressure on the deck and reducing lift at the rear axle. On a hatchback, a roof or tailgate spoiler extends the roofline, so the flow leaves at a clean, defined edge.

Unlike a wing, a spoiler works with the body surface rather than as a separate aerofoil in clean air, so its forces are smaller. Less rear lift steadies the car at speed, but any change at one end moves the aerodynamic balance. A car with much more grip at the rear than at the front tends to run wide in fast corners.

Check these points before ordering:

• Position and body: boot, tailgate and roof spoilers are mostly listed by model and years, and some titles add the door count. A three-door hatch and a four-door saloon take different parts.
• Material: polyester, a glass-fibre laminate shown as FRP in some titles, is stiff and easy to repair but needs careful preparation. ABS has a smooth moulded surface that takes paint well, and carbon is light and usually shows its weave under clear lacquer.
• Brake light: one spoiler carries a brake light, and a replacement brake light is listed separately. Where a spoiler covers the factory high-level brake light, it must provide a working one.
• Style: shapes copy factory sport models and well-known tuner kits.

Test-fit before painting, and use the factory mounting points where they exist. Any new hole in a boot lid or tailgate needs deburring, primer and a sealed fixing, or water and rust will follow. Feed brake light wiring through a grommet and check that the light works with the pedal. A heavier tailgate may need stronger gas struts, and the rear wiper must still sweep freely.