Rules & legality
What should I know before changing an exhaust or horn?
No Tarmac field guides · Updated 2026-09-12
Before you start: Keep the upgrade compatible with the vehicle's noise, emissions and equipment requirements. A louder sound or a successful pollution test is not proof that the complete setup complies.
General information, not legal advice. Confirm the requirements for your vehicle, route and travel date with the responsible authority.
Check equipment requirements
The Central Motor Vehicles Rules address horns in Rule 119 and silencers in Rule 120, alongside emissions requirements. Ask the supplier for evidence covering the proposed part and installation on your vehicle. Do not rely on a generic road-legal claim.
Explain what changes
Ask whether exhaust work removes or changes emissions-control equipment, sensors or factory calibration. For a horn, describe the device rather than asking about volume alone. Get the part number, installation specification and compliance documents before work starts.
Consider roads and venues
Discuss the change with your insurer and registering authority where appropriate. Competition equipment may have different intended uses, and a private venue can set its own noise conditions. Keep the agreed specification and inspection records. Choose a setup that works for the drive without imposing it on everyone nearby.
Before you decide
- Which noise and equipment requirements apply?
- Does the work change approved emissions equipment?
- What compliance evidence should the installer supply?
Official references
Check the issuing authority for later changes. Reviewed 2026-09-12.