How to Calculate Truck Tire Cost Per Mile

A tractor-trailer rolls on a lot of rubber, and every one of those tires wears a little with every mile. Tire cost per mile turns a big, lumpy bill (a full set of drives) into a small number you can set aside as you go and build into your rates.

The formula

Work it out per position group, since steers, drives, and trailer tires cost and wear differently.

Cost per tire life = tire price + mount, balance, and disposal, plus each retread and its install, minus any casing credit you get at the end.

Miles per tire life = miles from the new tread + miles from each retread.

Group cost per mile = number of tires × (cost per tire life ÷ miles per tire life).

Every tire turns every mile the truck runs, which is why you multiply by the count. Add the groups together for your total tire cost per mile, then multiply by your monthly miles for a monthly tire reserve.

Where the numbers come from

• Price and install: your dealer's quote, including mounting, balancing, valve stems, and the disposal or casing fee on the old tire.
• Tread life: your own records are best. If you don't have them, divide the miles a tire has run by how much tread depth it has lost, then work out how many miles you'll get down to the depth where you pull it.
• Retreads: the price per retread from your retreader, how many miles you get from each one, and how many times a casing usually passes inspection for your use.
• Casing credit: what a dealer or retreader pays for a worn casing, if anything.

Worked example

These prices and mileages are made up to show the math. They aren't typical figures. Use your own.

Steers: 2 tires at $550, plus $40 each to mount, balance, and dispose of, lasting 120,000 miles. Per tire: $590 ÷ 120,000 = $0.00492 a mile. Times 2 = $0.0098 a mile.

Drives: 8 tires at $500 plus $40, lasting 250,000 miles, then retreaded once for $220 plus $40, and the retread lasts 180,000 miles. Per casing, that's $540 + $260 = $800 over 430,000 miles, or $0.00186 a mile. Times 8 = $0.0149 a mile.

Trailer: 8 tires at $400 plus $40, lasting 200,000 miles. $440 ÷ 200,000 = $0.0022 a mile. Times 8 = $0.0176 a mile.

Total: $0.0098 + $0.0149 + $0.0176 = about $0.042 a mile. At 10,000 miles a month, set aside about $423 a month.

Without the retread, drives would cost 8 × ($540 ÷ 250,000) = $0.0173 a mile, and the total would be about $0.045 a mile, or about $447 a month. In this example the retread saves about $24 a month. Your numbers will differ, so run both ways.

Legal tread depth

Federal rules set a floor on how far you can run a tire. Tires on the front wheels of a truck or truck tractor need at least 4/32 of an inch of tread depth, measured at any point on a major tread groove. All other tires need at least 2/32 of an inch in a major tread groove. You can't run a tire with ply or belt material showing, tread or sidewall separation, a flat or an audible leak, or a cut that exposes the ply or belt. A regrooved tire rated to carry 4,920 pounds or more can't be used on the front wheels of a truck or truck tractor (49 CFR 393.75).

Those are legal minimums, not a plan. You may choose to pull tires sooner, for example to keep casings retreadable or for traction in bad weather. Whatever depth you pull at is what sets your tread life, so use the same number in your math.

Ways to lower the number

• Keep pressure right. Check it with a gauge on a schedule and set it to the tire maker's inflation table for your load.
• Watch alignment. Uneven wear on steers is often the first sign something is off.
• Protect your casings. A casing that can be retreaded is worth money. One that's been run too low or too hot isn't.
• Track every tire. Write down position, date, mileage, and tread depth at install and removal. After a year you'll know your real tread life instead of guessing.

Run your numbers

Put your own prices and tread life into the tire cost per mile calculator. Add the result to your maintenance reserve and your cost per mile, so every load pays for the rubber it wears off.