Why part-worn tyres are rarely the bargain they look

Start with the arithmetic

A part-worn typically has 4mm to 5mm of tread against 8mm on a new tyre. You are buying roughly 40% of the life for roughly 50% of the price of a new budget tyre.

That is a worse deal before you consider anything else, and there is quite a lot else to consider.

The bit you cannot inspect

The two things that ruin a tyre are running it flat and hitting something hard. Both leave damage inside the casing that is invisible from the outside.

A part-worn came off a vehicle for a reason, and nobody selling it knows what that reason was.

You are not buying tread. You are buying the last owner's driving, sight unseen.

What the law actually requires

Part-worns can be sold legally in the UK, but they must be marked, must have at least 2mm of tread, and must be free of specified damage. A significant share of those inspected in trading standards surveys fail at least one of those.

Legal and safe are not the same word, and the compliance record in this corner of the trade is not good.

When they are genuinely fine

A nearly-new tyre off a written-off car, sold by somebody who can tell you exactly where it came from, is a reasonable buy. They exist.

The problem is that you cannot tell that one from the others without the seller's honesty, and the price is the same either way.

What we would do

If the budget is tight, a new budget tyre is the better spend. It has full tread, a known history and a warranty, and it is not much more money.

We do not sell part-worns, so there is nothing in this for us either way. That is rather the point of writing it down.

What a legal part-worn looks like

It must be marked PART-WORN in letters at least 4mm high, permanently and legibly. It must have at least 2mm of tread across the full width. It must be free of cuts, bulges and exposed cord.

And it must have passed a pressure test at its rated inflation before sale. Most buyers have never heard of that last one and almost none of them ask.

If the tyre you are being offered is not marked, the seller is already breaking the rules and you are relying on their judgement about everything you cannot see.

Ask whether it has been pressure tested. The answer, and how it is given, tells you what you need to know.

Age matters more than tread

Rubber hardens with time whether or not the tyre is used. The four-digit code on the sidewall gives the week and year of manufacture, so 3419 is the thirty-fourth week of 2019.

A part-worn with plenty of tread can easily be eight or ten years old, at which point the compound has lost a meaningful amount of its wet grip regardless of how it looks.

Check the date code on anything second-hand. It is the one piece of information the seller cannot massage.