MilesheetTyres: the legal minimum, and why it is not the sensible one
1.6mm is the law. Braking distances start deteriorating well before that, and four illegal tyres is twelve points.
Tyres are the only part of a car touching the road, and the only safety component with a legal minimum most drivers can check in two minutes with a 20p coin.
The legal requirement
For cars, the tread must be at least 1.6mm across the central three-quarters of the tread, around the entire circumference.
Two details people miss. It is the central three-quarters, so healthy-looking outer edges do not save an illegal middle. And it is the whole circumference, so one bald patch fails the whole tyre.
Tyres must also be correctly inflated, free from dangerous cuts or bulges, and suitable for the use.
The penalty is per tyre
This is the part that surprises people: it is three penalty points and a fine per illegal tyre.
Four illegal tyres is twelve points, which is a ban, arrived at in one roadside stop without exceeding a single speed limit.
What the tread depth actually costs you
Wet braking from 50 mph, indicative stopping distances:
| Tread depth | Status | Relative wet stopping distance |
|---|---|---|
| 8mm (new) | New | Baseline |
| 5mm | Good | Slightly longer |
| 3mm | Recommended change point | Noticeably longer |
| 2mm | Legal, poor | Considerably longer |
| 1.6mm | Legal minimum | Substantially longer |
| Below 1.6mm | Illegal | 3 points and a fine, per tyre |
The penalty stacks
| Illegal tyres | Penalty points | Consequence |
|---|---|---|
| 1 | 3 | Fine |
| 2 | 6 | Fine; licence revoked if within 2 years of passing |
| 3 | 9 | Close to a ban |
| 4 | 12 | Ban, from a single roadside stop |
Why 1.6mm is not where you should be changing them
The legal minimum is a floor, not a target. Wet braking performance falls off well before it — most testing shows meaningful deterioration below about 3mm, with stopping distances lengthening considerably by the time you reach the legal limit.
Many manufacturers and safety organisations recommend replacing at 3mm. That is not an upsell so much as an acknowledgement that the legal minimum was set as an enforcement threshold, not as the point at which a tyre stops working well.
The 20p test
Insert a 20p coin into the main tread grooves. If the outer band of the coin is hidden, the tread is above roughly 1.6–1.8mm. If you can see the band, the tyre is at or near the limit and needs looking at properly with a depth gauge.
Do it at several points around the tyre and across its width, not once.
Pressure, which costs money as well as safety
Under-inflated tyres wear faster at the edges, increase rolling resistance and cost fuel. Pressure drops naturally over time and falls further in cold weather — roughly 1–2 PSI for every 10°C.
Checking monthly is the single cheapest thing you can do for both safety and economy. If you keep a fill-up log, an unexplained dip in MPG across a couple of tanks is often exactly this.
For business vehicles
If you or your employees drive for work, tyre condition is part of the duty of care around work vehicles, not just an MOT question. A vehicle used for work is expected to be roadworthy every day, not on the day it was tested.
Sources
- GOV.UK — Getting an MOT
- The Highway Code — Annex 6: vehicle maintenance, safety and security
- GOV.UK — Penalty points (endorsements)
- GOV.UK — Check the MOT history of a vehicle
General road safety information, not legal advice.