Cost per kilometre — new against retread

Four figures are required: a price and an expected life for each of the two options. The two optional fields — tyre positions in the fleet, and kilometres per position per year — turn the per-kilometre difference into an annual figure, which is the number that gets a decision made.

Use prices on the same basis for both, normally your buying price excluding VAT. Use life in kilometres to your own removal point, not to the legal limit and using your own operating records where available. If you pull steer tyres at 4 mm because you retread the casings, that is where the life ends for this calculation.

It works for any two options, not just new against retread: premium against mid-range, two patterns on the same axle, or the same tyre on two different routes.

Option A, a premium new drive tyre at £310 expected to give 180,000 km. Option B, a retread at £165 expected to give 110,000 km. A fleet of 120 positions doing 90,000 km each per year.

• Option A: 310 over 180,000 km = 0.17p per km
• Option B: 165 over 110,000 km = 0.15p per km
• Difference: 0.02p per km in favour of option B
• Across the fleet: £2,400 a year

A £145 gap in purchase price comes down to two hundredths of a penny per kilometre. That is the point of the exercise: the price difference that looks decisive on a quotation is small once it is spread over the distance each tyre covers.

Now put the casing back in. If the premium casing is worth £40 to you at removal because it retreads and the budget one does not, enter £270 for option A instead of £310. Both options then come out at 0.15p per km and the fleet saving disappears entirely. Same tyres, same lives, different answer — because the casing was worth counting.

The arithmetic is a single division: price divided by life. Everything else is what you decide to put into the price and the life.

Life is the number that dominates. A ten per cent error in expected life is a ten per cent error in the answer, and life varies far more than price does — by axle position, route, vehicle, driver, and above all by pressure discipline. Take life figures from your own removal records. Check that expected life figures reflect comparable operating conditions.

Nothing else is modelled. No fitting labour, no downtime, no casing value unless you build it into the price, no cost of capital, no VAT handling. If a cost differs between the two options, it has to go into the price you type or it will not appear in the answer.

Rounding. The two pence-per-kilometre figures and the difference are shown to two decimal places, but the fleet total is calculated from the unrounded values. A difference displayed as 0.02p may be 0.022p underneath, so the annual figure will not always reconcile exactly against the rounded pence.

The fleet total is a flat multiplication — difference times positions times kilometres per position. It assumes every position runs the same distance on the same option, which no fleet does.

Fuel is missing, and on a truck fuel is the largest number in the equation. Fuel cost per kilometre is many times tyre cost per kilometre, so a small difference in rolling resistance between two tyres can be worth more than the entire purchase price gap. A tyre that wins on this page can lose on the fuel bill. Where rolling resistance differs between the options, weigh the EU label figures alongside this calculation rather than deciding on it alone.

Casing risk is missing. A failure on the motorway costs recovery, downtime, damage to bodywork and possibly a missed delivery, and none of it appears in pence per kilometre. Comparing a casing you know against one you do not on price per kilometre alone is a false comparison.

Multiple lives are missing. A premium casing that takes two retreads is a completely different proposition from one that takes none. Model it by treating the whole cycle as one price over the total kilometres — original tyre plus two retreads, divided by the sum of the three lives.

Regrooving is missing. On a regroovable truck tyre, a regroove adds distance for a small labour cost and shifts cost per kilometre noticeably. Add the kilometres to the life and the cost to the price.

Use cost per kilometre alongside fitment suitability, fuel use, casing quality and downtime when comparing options.