{
  "slug": "semi-trailer-maintenance",
  "title": "Semi Trailer Maintenance: The Trailer's Systems",
  "description": "A semi trailer has its own systems to maintain, separate from the tractor: brakes and ABS, wheel ends, tires, suspension, landing gear, and lighting.",
  "track": "maintenance",
  "kind": "article",
  "isRegulatoryAdjacent": false,
  "publishedAt": "2026-10-19",
  "updatedAt": "2026-10-22",
  "cfr": [],
  "related": [
    "trailer-brake-adjustment",
    "trailer-abs-module",
    "trailer-wheel-end-maintenance",
    "trailer-air-ride-suspension",
    "trailer-landing-gear-repair",
    "semi-trailer-lighting-and-wiring",
    "semi-truck-and-trailer-tires",
    "semi-truck-tire-pressure-and-inflation",
    "air-brake-system",
    "trailer-abs-light",
    "slack-adjuster-adjustment",
    "brake-chamber-air-leaks"
  ],
  "topics": [
    "brakes_air",
    "tires_wheels",
    "suspension",
    "chassis_trailer_body",
    "lighting_electrical"
  ],
  "nextStep": {
    "kind": "related",
    "target": "trailer-brake-adjustment",
    "text": "See how trailer brakes are inspected and adjusted"
  },
  "sources": {
    "citations": [],
    "bcpRole": "Blue Collar Parts records the work and sends the report to your customer. It does not perform, certify or approve inspections.",
    "reviewed": "2026-10-22",
    "reviewedEdition": null,
    "reviewedText": "Reviewed 2026-10-22"
  },
  "url": "https://shopbluecollarparts.com/kb/semi-trailer-maintenance",
  "markdownUrl": "https://shopbluecollarparts.com/kb/semi-trailer-maintenance.md",
  "body": "A semi trailer carries its own set of systems to maintain, separate from the tractor that pulls it. A tractor and trailer share the road and share the air brake system, but the trailer has its own brakes, its own wheel ends, its own suspension, and its own lights — and they wear and fail on their own schedule, not the tractor's. This page is the map of the trailer's systems for a service provider. Each section links to a page that goes deeper.\n\n## What does semi trailer maintenance cover?\n\nA trailer maintenance visit is usually grouped into these systems.\n\n1. **Brakes and ABS.** The trailer's half of the [air brake system](/kb/air-brake-system) — supply and emergency lines, the relay-emergency valve, spring brakes, slack adjusters — plus the trailer's own antilock brake module. See [trailer brake adjustment](/kb/trailer-brake-adjustment) and [trailer ABS troubleshooting](/kb/trailer-abs-module).\n2. **Wheel ends.** The hubs, bearings and seals that carry the trailer's weight and let the wheels turn freely. See [trailer wheel end maintenance](/kb/trailer-wheel-end-maintenance).\n3. **Tires and the tire inflation system.** Trailer tires carry load without an engine to signal a problem through the drivetrain, which is why many trailers add a tire inflation system that keeps the tires at their set pressure or flags one that's low. At this level, the system is: tires, the wheel valve or hose that feeds each one, and a controller or gauge that reports pressure or flow. Where a trailer has an inflation system, its condition is usually recorded with the tire and wheel work. See [semi truck and trailer tires](/kb/semi-truck-and-trailer-tires) for the tire and wheel system, and [trailer tire inflation systems](/kb/semi-truck-tire-pressure-and-inflation) for how the inflation system works.\n4. **Suspension.** On most semi trailers, an air-ride suspension with air springs, a height control valve, shocks and pivot bushings. See [trailer air ride suspension](/kb/trailer-air-ride-suspension).\n5. **Landing gear.** The legs that support the trailer when it's uncoupled, and the gearbox and crank that raise and lower them. See [trailer landing gear repair](/kb/trailer-landing-gear-repair).\n6. **Lighting and the 7-way connector.** The trailer's marker, clearance, turn and brake lights, and the connector that carries power and signals from the tractor. See [semi trailer lighting and wiring](/kb/semi-trailer-lighting-and-wiring).\n\n## Why the trailer gets its own maintenance record\n\nA tractor and trailer are often serviced on different schedules, by different service providers, and sometimes for different customers. A trailer-specific record keeps the trailer's own history — by VIN or unit number — intact no matter which tractor pulled it that week, or which service provider saw it last.\n\n## Use the manufacturer's documentation\n\nTrailer hardware differs by manufacturer and by component: an axle maker's wheel-end documentation, a suspension maker's ride-height specification, an ABS maker's diagnostic procedure. This page is a map of what to maintain, not a service manual for any one trailer.\n\n## Log the work in Blue Collar Parts\n\nA technician who services a trailer can log the work in Blue Collar Parts and send the record to their customer, who confirms it. [Learn what Blue Collar Parts is](/kb/what-is-blue-collar-parts).\n\n---\n\n*This page describes semi trailer systems in general terms. It is not a service manual and does not establish regulatory compliance. Use the equipment manufacturer's current service documentation for equipment-specific procedures.*",
  "license": "CC BY 4.0",
  "licenseUrl": "https://creativecommons.org/licenses/by/4.0/"
}