Rules & legality
What should I check before fitting bigger tyres?
No Tarmac field guides · Updated 2026-09-12
Before you start: Choose tyres for the work your 4x4 does. Establish the manufacturer's approved options and check the implications for fitment, road use and cover before changing size.
General information, not legal advice. Confirm the requirements for your vehicle, route and travel date with the responsible authority.
Check approval for your variant
A size offered on another variant is not automatically approved for yours. Section 52 is relevant when a change affects registered particulars. Ask for documentation covering your model rather than relying on a universal percentage rule from a tyre calculator.
Check the complete wheel-and-tyre package
Have the installer check rim compatibility, load and speed ratings, clearance through steering lock and suspension travel, and the spare. Ask about speedometer accuracy, gearing and pressure recommendations. Include wheel offset in the discussion rather than judging the tyre in isolation.
Decide before the old tyres come off
Put the exact size, wheel specification and intended use on the quote. Ask your RTO whether approval is required and your insurer how the change will be recorded. If the setup needs body or suspension changes to fit, review those together before committing.
Before you decide
- Which sizes are approved for my exact variant?
- Does this wheel-and-tyre change require approval?
- What documents should I retain for insurance?
Official references
Check the issuing authority for later changes. Reviewed 2026-09-12.