Tires are one of the biggest running costs on a school bus after fuel and the driver, and one of the most common reasons a bus fails an inspection. Replace them too early and you throw away tread you paid for; too late, and you risk a blowout with children on board, or a bus parked by an inspector.
There's no single mileage at which every school bus tire should be replaced. A school bus tire replacement schedule is really a check schedule: measure tread, look at age and damage, keep the pressure right, and replace when one of them says so. Here's what to check, how often, and the limits that apply.
Tread depth: the federal minimums
The federal rules for commercial vehicles (49 CFR 393.75) set the minimum tread depth, measured in a major tread groove:
| Position | Minimum tread | Also |
|---|---|---|
| Front (steer) tires | 4/32 inch | On a bus, no regrooved, recapped or retreaded tires on the front wheels |
| Other tires (drive, rear) | 2/32 inch | Retreads are allowed in these positions |
Many states and districts set their own, sometimes stricter, rules for school buses, and inspectors can also put a bus out of service for cuts, bulges, exposed cord or a flat. Most fleets replace well before the legal minimum, for example steer tires at 6/32 or 8/32 inch, because wet-road grip falls off as tread gets shallow.
Tip: Measure tread with a gauge, not a coin, and in more than one groove: uneven wear on one side points to alignment, and wear in the middle or on both edges points to pressure.
Tire age and the DOT date code
Rubber ages even on a bus that barely moves, such as a spare or a summer-parked bus. Every tire has a DOT code on the sidewall ending in four digits: the week and year it was made (2422 is the 24th week of 2022). There's no federal age limit for bus tires, but tire makers publish their own advice, often a closer look each year once a tire is about five years old, and replacement at a set age whatever the tread. Follow the maker's advice for your tires, and look for cracking in the sidewall and between the treads.
Pressure, especially in winter
- Check pressure cold, before the bus has been driven, against the number on the bus's tire label, not the sidewall maximum.
- Cold weather drops pressure: roughly 1 PSI for every 10°F colder. A bus set in September can be well under by January.
- Under-inflated tires wear faster on the edges, run hot and fail more often. Duals are the worst: a soft tire next to a good one gets dragged along.
- Valve caps on, and valve stems checked: a cracked stem leaks slowly and is easy to miss.
A tire check schedule
| How often | Who | What |
|---|---|---|
| Every pre-trip | The driver | Look for flats, cuts, bulges, objects in the tread, missing lug nuts; a quick look at duals |
| Every week or month | The shop | Pressure on every tire with a gauge, tread depth, valve stems, wheel nuts |
| Every service | The mechanic | Wear pattern, alignment, rotation if your tires allow it, the DOT date |
| Every winter and summer | The shop | Pressure after the temperature change, spare buses' tires and age |
When to replace
- Tread at your own replacement point (above the legal minimum), measured in more than one groove.
- Any damage that shows the cord, a bulge, a sidewall cut, or a repair outside what the maker allows.
- Age past the tire maker's advice, or cracking, whatever the tread.
- Uneven wear that can't be fixed by alignment or pressure.
- Replace in matching pairs on an axle, and match duals in size and tread.
Good to know: Your state may set its own tire rules for school buses and check them on its yearly or twice-yearly inspection. Check your state's requirements, and our inspection requirements guide.
Doing it in FleetCommander
Scheduled checks. On Maintenance, New schedule has a Tire inspection preset, every 30 days, for each bus. Change the days to fit your shop, or add Every (miles). It shows Due soon, Due and Overdue, and Create work order turns it into a job. When the work order is completed, it goes into Service history with the date and cost.
Daily checks. Your drivers' pre-trip checklist is yours to write on Inspections › Templates, so add the tire items your state asks for, and tick Safety-critical on the ones that should park the bus. A failed item becomes a defect with its photo, in the Tires & wheels category, for the shop to fix.
Stock and cost. Keep spare tires in Parts with a minimum, and they're flagged Low stock when you're down to it. Log tire purchases as Expenses in the Tires category, and work orders carry the labor and parts, so the Vehicle costs and Maintenance costs reports show what each bus's tires cost you. See the Maintenance guide, the Defects guide and the Parts guide.
Ava (Beta), the assistant in the app, answers Any open defects? or What maintenance is due?. More on her page.
Related reading
Questions people ask
- What is the minimum tread depth for school bus tires?
- Under the federal rules for commercial vehicles, 4/32 inch on the front (steer) tires and 2/32 inch on the others, measured in a major groove. Many states and fleets set a higher point for replacement.
- Can a school bus have retread tires?
- Not on the front wheels: the federal rules don't allow regrooved, recapped or retreaded tires on a bus's front wheels. Retreads are allowed in other positions, unless your state or district says otherwise.
- How old can school bus tires be?
- There's no federal age limit, but tire makers publish their own advice on inspecting and replacing older tires. Read the age from the last four digits of the DOT code (week and year).
- How often should school bus tires be checked?
- The driver looks at them on every pre-trip; the shop checks pressure and tread with a gauge every week or month, and looks at wear, alignment and age at every service.