---
slug: trailer-air-ride-suspension
title: "Trailer Air Ride Suspension: Air Springs, Height Control and Alignment"
description: "Trailer air ride suspension maintenance covers the air springs, height control valve, shocks, bushings and pivots, plus axle alignment at a category level."
track: maintenance
kind: article
isRegulatoryAdjacent: false
publishedAt: 2026-10-19
source: https://shopbluecollarparts.com/kb/trailer-air-ride-suspension
license: CC BY 4.0
---

# Trailer Air Ride Suspension: Air Springs, Height Control and Alignment

Most semi trailers ride on an air suspension, and most of what can go wrong with it shows up as the trailer sitting at the wrong height, riding harshly, or wandering on the road. Trailer air ride suspension maintenance works through the parts that set and hold ride height, and the parts that locate the axle underneath it.

## Air springs

The **air spring** (air bag) carries the trailer's weight on a column of air instead of a steel spring. A damaged, chafed or leaking air spring loses its ability to hold height and load evenly, and a spring that's rubbing against the frame, another component, or itself as it travels will keep wearing until it fails. Check an air spring for cracking, chafing, and contact with anything around it through its full range of travel, not just at ride height.

## The height control valve

The **height control valve** (ride height or leveling valve) reads the distance between the axle and the frame and adds or releases air to the springs to hold the trailer at its set height. A valve that's stuck, disconnected, or linked with a bent or loose linkage arm will leave the trailer riding too high, too low, or unresponsive to load changes. Because the valve is set by its linkage geometry, a bent arm or a valve that's been bumped out of position can throw off ride height even when the valve itself works correctly.

## Shocks, bushings and pivots

Shock absorbers control how the suspension moves, not how much weight it carries — a trailer can sit at the correct height on failed shocks and still ride and handle poorly. Bushings and pivot points let the suspension's arms move while keeping the axle located; worn, cracked or missing bushings let the axle shift under load and braking, which shows up as uneven tire wear and a trailer that doesn't track straight.

## Axle alignment

Axle alignment keeps the trailer's axle (or axles, on a multi-axle trailer) square to the frame and to each other. A misaligned axle wears tires unevenly, drags, and can make the trailer pull or dog-track down the road. Alignment is measured and adjusted with equipment built for the job and against the specification for that trailer and suspension; this page describes what alignment does, not how to measure or set it.

## What a suspension inspection looks for

A suspension check works through the same list each time: air springs for damage and chafing, the height control valve and its linkage for correct operation, shocks for leaks and mounting, bushings and pivots for wear and play, and the trailer's ride height and tracking as a whole. The suspension and axle manufacturer's documentation gives the specifications and tolerances for the specific components on the trailer.

## What should the service record show?

A record of trailer suspension work should show:

- the ride height found and after any adjustment, measured where the suspension maker specifies;
- the condition of each air spring, shock and bushing, by axle and side;
- height control valve and linkage findings;
- whether alignment was checked, and the result, if it was;
- parts replaced, with part numbers.

A record kept by the trailer's own unit number or VIN stays with the trailer, whichever tractor pulled it.

## Log the work in Blue Collar Parts

A technician who does this work can log it 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).

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*This page describes trailer air ride suspension 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 specifications and procedures.*

## Sources

What BCP does here: Blue Collar Parts records the work and sends the report to your customer. It does not perform, certify or approve inspections.
Reviewed 2026-10-19