One tyre, fully fitted

A fully fitted price is the number to compare, because it is what leaves your account. At a national retailer it covers the tyre, taking the old one off the rim, a new valve, fitting the new tyre, balancing the wheel, disposing of the old casing and VAT on all of it. For 205/55 R16, the size on more UK cars than any other, that comes to £49 to £110 a corner depending on the brand tier you choose.

Balancing matters more than it sounds. A tyre is never perfectly even in weight around its circumference, so the fitter spins the wheel on a machine and clips small weights to the rim until it runs true. Skip it and you feel a shimmy through the steering at motorway speed, and the tyre wears in patches.

If you buy the tyre somewhere else and bring it in, you pay for the labour on its own. Kwik Fit publish £20.50 per tyre for fitting, balancing, a valve and disposal, which is the figure to add to any online price before you decide it is a bargain.

At least 1.6mm, measured in the main grooves, across a continuous band covering the central three quarters of the tread and all the way round. That limit applies to cars with up to 8 passenger seats, vans up to 3,500kg and light trailers. Motorcycles and large vehicles work to 1mm instead.

The outer eighth on each shoulder is not part of the legal measurement, so a tyre worn bald on its inside edge can still measure legal across the middle. That is exactly the tyre that fails in the wet, because the shoulder is where the car leans when you corner. Wear on one edge usually points to the alignment, and replacing the tyre without correcting the geometry just wears the new one out the same way.

The penalty is per tyre, not per car. GOV.UK puts it at a fine of up to £2,500 and 3 penalty points for each tyre below the limit, so four worn tyres are four offences. A new driver who reaches 6 points within 2 years of passing loses the licence, which means two illegal tyres at one roadside check can end a new licence on their own.

Tyres are section 5.2.3 of the DVSA inspection manual. The tester looks only at the tyres on the road wheels on the day, so a spare in the boot is never failed; if its condition is poor the tester tells you rather than recording a defect. Cuts are checked with a blunt tool opened gently to see whether the damage reaches the ply or cord, and tread is measured in the primary grooves that carry wear indicators, not the shallower secondary grooves.

Radial and cross-ply tyres must not share an axle, and two tyres of different sizes on the same axle fail. A run flat tyre next to a conventional one is allowed, although DVSA says it is not recommended. The load index and speed rating on the sidewall are not checked on an ordinary car at all: the manual applies those two checks to vehicle classes 5 and 7 only, and a car is tested in class 4.

Cars first used from 1 January 2012 also have the tyre pressure monitoring warning checked. A system that has failed or clearly does not work is a major defect. If the tester cannot tell whether the lamp is reporting a fault or simply a low tyre, it becomes an advisory instead.

Within one size, brand tier does most of it. The £49 to £110 range for 205/55 R16 is the spread from a budget brand at £48.64 to a Michelin CrossClimate all season tyre at £109.99, both fully fitted at Blackcircles. The legal requirements are identical for both. What you buy with the extra money is wet grip, noise and how slowly the tread wears, and the tyre label on a retailer's listing grades the first two.

Across sizes, rim diameter moves the price fastest. An 18 inch or 19 inch wheel on a newer crossover takes a tyre that can cost more than the top of this range, and no published fully fitted figure for those sizes could be verified, which is why this page does not print one. The same goes for run flat tyres, reinforced tyres with a higher load rating and 4x4 patterns.

The sidewall tells you everything you need, and it is the easiest thing to get wrong when ordering online. Read it off the tyre currently on the car, then check it against the handbook or the placard in the driver's door opening, because a previous owner may have fitted the wrong size.

Yes, with conditions set by the Motor Vehicle Tyres (Safety) Regulations 1994. A part-worn tyre offered for sale must have its original tread grooves at least 2mm deep across the full breadth of the tread and all the way round, which is more than the 1.6mm you need to drive on. It must be marked PART-WORN in capital letters at least 4mm high, applied permanently and legibly but not by cutting or hot branding. It must also be free of any cut over 25mm or 10 per cent of the section width, any lump or bulge, and any exposed ply or cord.

The trouble is what the rules cannot tell you. A part-worn tyre has an unknown history, and the tread depth a seller advertises says nothing about age, a repaired puncture or a night spent run flat after a blowout. If the saving over a new budget tyre is a few pounds, the budget tyre with a full tread is usually the better buy.

A van up to 3,500kg is held to the same 1.6mm as a car, so a small panel van and a hatchback are measured alike. Motorcycles and large vehicles need 1mm across a continuous band of three quarters of the tread breadth instead.

Tyre age is the rule that surprises people. Since 1 February 2021 a tyre more than 10 years old is banned from the front steered axles of goods vehicles over 3.5 tonnes, buses and coaches, and from any single wheel axle of a minibus. It does not apply to private cars. An old tyre on a car is legal if its tread and structure pass, although rubber hardens with age and a tyre that has sat on a caravan or a garage car for a decade deserves suspicion however deep its tread.

In England, Scotland and Wales the MOT fee for a car is capped at £54.85, and a car that fails only on tyres can go for a free partial retest if you bring it back to the same centre before the end of the next working day. Wheels and tyres are on DVSA's list of items that qualify.

Northern Ireland runs its own test at DVA centres, and a tyre failure there has a sharper edge: nidirect says a car that fails is treated as not roadworthy and should not be on the road, even with time left on its old certificate. The retest must be applied for within 21 days and is charged at £29.50 for a car, so fit the tyres before you book rather than after.

Most of the money people waste on tyres comes from believing something about them that is not in the rules.