Part-worn tyres win on the sticker price. The case for them falls apart, though, once the sum is done properly, not on what a tyre costs to buy, but on what it costs to use.
Usable tread is the real measure
A tyre is only useful down to the 1.6mm legal limit, so what matters is how much tread sits above that line:
- A new tyre starts at around 8mm, roughly 6.4mm of usable tread
- A part-worn at 3mm has about 1.4mm of usable tread
- A part-worn at the 2mm sale minimum has barely 0.4mm left
So a part-worn often delivers half a new tyre's life or less, sometimes far less.
Cost per mile, not cost per tyre
Put price against usable tread and the picture changes. Take an illustrative example, round figures, just to show the maths, not real prices:
| Price | Usable tread | Cost per usable mm | |
|---|---|---|---|
| Part-worn | £25 | 1.4mm | ~£18 |
| Budget new | £55 | 6.4mm | ~£9 |
On those figures the "cheap" part-worn works out at roughly twice the cost per millimetre of the new tyre. The exact numbers vary, but the pattern is consistent, which is why safety bodies describe part-worns as a false economy.
What new tyres add
The value gap is only part of it. A new tyre also brings:
- Full tread and the longest service life
- A manufacturer warranty
- A known history, no hidden impacts, repairs or ageing
A part-worn offers none of these, plus the risk of buying one of the many that are sold illegally.
The verdict
For most drivers, a budget new tyre is the better choice than a part-worn, closer in price than it first looks, longer-lasting, and without the unknowns. A new tyre, the kind sold online by a retailer such as Tyres.co.uk, comes with full tread, a warranty and a clean history, which is exactly what a part-worn cannot promise.
From the workshop: when I show someone the cost-per-mile sum, the appeal of part-worns usually disappears. They came in to save thirty quid and leave realising the new tyre was barely dearer over its life, and a lot less of a gamble.
Sources and accuracy. The usable-tread and cost-per-mile framing here reflects TyreSafe guidance at the time of writing; the worked example uses illustrative round figures, not real prices. Anything safety-critical should be confirmed against current official guidance. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
Are part-worn tyres cheaper than new?+
Only on the day. Part-worns cost less upfront, but they come with far less usable tread, so worked out per millimetre of tread, or per mile, they are often no cheaper than a budget new tyre, and sometimes dearer.
How much usable tread does a part-worn tyre have?+
A new tyre starts at around 8mm, with about 6.4mm usable before the 1.6mm limit. A part-worn sold at 2mm has only about 0.4mm of usable tread left, and even one at 3 or 4mm gives roughly half a new tyre's life or less.
Why do safety experts recommend new over part-worn?+
Because a new tyre offers full tread, a manufacturer warranty and a known history, while a part-worn offers a fraction of the life and a past you can't verify. Per mile of use, the budget new tyre is usually both safer and better value.
Is a budget new tyre better than a part-worn?+
For most drivers, yes. A budget new tyre gives full tread, a warranty and a clean starting point at a price that is often close to a decent part-worn once usable life is taken into account, without the unknowns or the risk of an illegal sale.