Topic 3 of 14 · Tyres
Tyres, brakes and what the dashboard is telling you
The legal tyre minimum, the faults you can feel through the controls, and what to do when a warning light appears.
By the end of this lesson
- State the legal minimum tread depth and where it is measured
- Recognise common brake, tyre and suspension faults from how the car behaves
- Respond correctly to a red or amber dashboard warning
Tyres
Four contact patches, each roughly the size of a postcard, carry everything the car does — accelerating, braking and steering.
The legal minimum is 1.6 mm of tread depth across the central three-quarters of the breadth and around the entire circumference. Below that is an offence, with a fine and penalty points for each tyre.
Most tyre advice suggests replacing at around 3 mm, because wet performance degrades well before the legal limit.
Check regularly:
- Pressure, when the tyres are cold. Under-inflation makes the steering vague, wears the edges and can overheat the tyre. Increase pressures as the handbook advises when carrying a heavy load.
- Tread depth, across the width — uneven wear points at pressure or alignment problems.
- Cuts and bulges in the sidewall. These cannot be repaired. The tyre must be replaced.
Brakes
You will usually feel a brake fault before you see one.
- Pulling to one side under braking — one side is braking harder. A sticking caliper, contaminated pads, or badly mismatched tyres.
- A spongy or long pedal — air or a leak in the hydraulic system. This is the one that can fail completely and without warning.
- Grinding or squealing — worn pads or discs.
- A pedal that sinks slowly under steady pressure — a leak.
Any of these means the car goes to a garage before it goes anywhere else.
After driving through deep water, expect the brakes to be less effective. Test them gently, then dry them with light pressure while moving slowly, checking your mirror first.
Warning lights
The colour is the instruction.
Red: stop as soon as it is safe and find out why. Amber: a fault to deal with soon.
Red lights cover the things that destroy engines or remove your ability to stop — oil pressure, brake system, engine temperature, charging. Loss of oil pressure feels completely normal right up to the moment the engine seizes.
Amber lights, including the engine management light, usually mean the car is driveable but something needs diagnosing. An engine management light will also fail an MOT emissions test.
The habits worth having
Weekly, or before any long journey: tyre pressures and tread, oil and coolant levels, screen wash, and a walk round checking every light with someone operating them.
Every time you get in: notice what the dashboard does as the car starts. The lights that should go out, and the ones that stay on, are the fastest health check you will ever get.
The three things to remember
- Tyres must have at least 1.6 mm of tread across the central three-quarters of the breadth and around the whole circumference.
- Red warning lights mean stop and investigate. Amber means a fault to deal with soon.
- A car that pulls under braking, feels spongy on the pedal or bounces after a bump has a safety-critical fault.
⚠ The common mistake
Waiting until the MOT to find problems. An MOT certifies the vehicle's condition on the day of the test, not for the following twelve months.
On the road
A tyre at 1.7 mm is legal. Its wet braking distance is already substantially worse than a new tyre's, and you will find that out at the moment you most need it not to be true.
Check you have it
Answer these without scrolling back up. Retrieving something from memory is what makes it stick — rereading feels productive but does far less.
Preparing your questions…
Sources checked for this page
- The Highway Code — Annex 6, vehicle maintenance, safety and security
We summarise official guidance in our own words. Where the rules matter legally, check the official source. This site is not affiliated with DVSA.