What a Hendrickson suspension is and where you'll find it
A Hendrickson suspension is an air suspension system made by Hendrickson International, a company that designs suspension components for heavy trucks and trailers. You won't find one on a passenger car — these suspensions are built into commercial vehicles like semi-trucks, dump trucks, and flatbed trailers that carry heavy loads on highways and job sites.
The system uses air springs (flexible rubber and metal chambers filled with compressed air) instead of traditional steel coil springs. This design lets the suspension adjust automatically as the truck's load changes, keeping the vehicle level whether it's empty or fully loaded. Hendrickson suspensions are common on Class 8 trucks — the largest commercial vehicles on the road — because they handle weight distribution better than older spring-based systems.
If you drive a commercial truck or own a trucking business, understanding how this suspension works helps you recognize when maintenance is needed and what repairs might cost. If you're shopping for a used commercial vehicle, knowing whether it has a Hendrickson system tells you something about its design and maintenance history.
Key Takeaways
- Hendrickson suspensions use compressed air springs instead of metal coils, which allows them to adjust automatically as a truck's load changes.
- These systems are standard on heavy commercial trucks and trailers, not on passenger vehicles or light trucks.
- Air suspensions provide a smoother ride and better weight distribution than traditional suspensions, but they require regular maintenance of air lines and springs.
- Common repairs include replacing air springs, fixing air leaks, and servicing the compressor that pressurizes the system.
- A failing Hendrickson suspension can affect braking, steering, and load stability, making prompt repair important for safety.
How the air springs and compressor work together
The core of a Hendrickson suspension is the air spring — a sealed chamber made of reinforced rubber and metal that holds pressurized air. As the truck's weight presses down, the air inside compresses, absorbing the shock. When weight is removed, the air expands and pushes back, returning the suspension to its original height. This happens continuously as the truck moves, which is why the ride feels smoother than a steel-spring suspension.
An onboard air compressor keeps the system pressurized. The compressor draws air from outside, pressurizes it, and stores it in an air tank. Sensors monitor the pressure constantly. If pressure drops — usually because of a small leak — the compressor automatically kicks in to restore it. This self-adjusting feature is what makes the suspension level the vehicle even when loads shift or change.
The system also includes air lines (rubber and metal tubing) that carry pressurized air from the tank to each air spring, and a series of valves that control how much air reaches each spring. If any of these components fails, the suspension loses pressure and the truck sags on one side or sits lower than normal.
Signs that a Hendrickson suspension needs repair
The most obvious sign is a truck that sits lower on one side than the other, or a vehicle that leans noticeably when parked. This usually means one or more air springs have lost pressure. You might also notice the truck bouncing more than usual, or a hissing sound near the wheels — that's air escaping from a leak.
If the compressor is failing, you may hear it running constantly, even when the truck is parked and the engine is off. The air tank may also develop rust or corrosion on the outside, which signals that moisture is building up inside — a sign the compressor's drying system isn't working properly.
Brake problems can also point to a suspension issue. Many commercial trucks use the same air system for both suspension and brakes. If the air pressure drops too low, braking power decreases, and the brake warning light on the dashboard will illuminate. This is a safety issue that requires when ready attention.
Common repairs and what they involve
Replacing an air spring is the most frequent repair. A technician removes the wheel and brake assembly, disconnects the air line, unbolts the old spring, and installs a new one. The job typically takes one to three hours per spring, depending on the truck's design. Because air springs come in different sizes and pressure ratings for different truck models, ordering the correct part is important.
Fixing air leaks involves finding where air is escaping — usually at connection points where air lines join the tank or springs — and either tightening the fitting or replacing the damaged line. Small leaks can be hard to locate; technicians often use soapy water to spot bubbles that reveal where air is leaking out.
Compressor replacement is more involved and more expensive. The compressor bolts to the engine or frame and connects to multiple air lines. Removing it requires disconnecting these lines, draining the air tank, and unbolting several fasteners. Installation is the reverse process, followed by a pressure test to may support the system holds air.
Air tank maintenance includes draining moisture that accumulates inside. Most tanks have a drain valve at the bottom that a technician opens periodically to release water. If moisture isn't removed, it can corrode the tank from the inside and damage the compressor.
Why Hendrickson suspensions are popular despite maintenance needs
Commercial truck operators choose Hendrickson suspensions because they reduce wear on cargo and the truck itself. The smoother ride means freight arrives in better condition, which matters for fragile goods. The automatic load-leveling feature also improves braking and steering — the truck handles more predictably whether it's empty or fully loaded.
Over the life of a truck, an air suspension typically costs less to maintain than a traditional spring suspension, even though individual repairs can be expensive. Air springs last longer than steel springs, and the system's self-adjusting nature means less strain on other components like shock absorbers.
Resale value is another factor. Used commercial trucks with well-maintained Hendrickson suspensions often command higher prices because buyers know the suspension is reliable and has years of service life remaining.
Maintenance steps to extend suspension life
Regular air tank draining is the simplest preventive step. Most manufacturers recommend draining the tank weekly or monthly, depending on how much the truck runs. This removes moisture before it causes rust or compressor damage.
Visual inspections catch problems early. Check the truck's stance when parked — it should sit level side to side and front to back. Listen for unusual compressor noise or air hissing. Look for corrosion on the air tank or visible damage to air lines.
Keeping the air filter clean helps the compressor work efficiently. A clogged filter forces the compressor to work harder and can shorten its life. Most filters should be inspected every 50,000 to 100,000 miles and replaced as needed.
Professional inspections during regular maintenance — such as when the truck is serviced for oil changes or brake work — catch small issues before they become expensive repairs. A technician can pressure-test the system and check for leaks that might not be obvious to an untrained eye.
Cost expectations for repairs and replacement
Air spring replacement typically costs between $300 and $800 per spring, depending on the truck model and whether you're using original Hendrickson parts or aftermarket alternatives. A truck with multiple springs on each axle might need several replaced at once, which adds up quickly.
Compressor replacement is more expensive, generally ranging from $1,500 to $3,500 including labor, depending on how accessible the compressor is on your specific truck model and whether additional components need replacement.
Air line repairs are usually the least expensive, often $100 to $400 depending on the line's location and length. Air tank draining and maintenance is inexpensive — often under $100 — which is why regular preventive maintenance saves money over time.
Labor costs vary by region and shop. Independent truck repair shops are often less expensive than dealerships, but make sure any shop you choose has experience with Hendrickson systems specifically.
Frequently Asked Questions
Can I drive a truck with a failing air suspension?
You can drive it short distances to reach a repair shop, but it's not safe for highway use. A sagging suspension affects braking, steering, and stability, especially when the truck is loaded. If the air system also powers the brakes, low pressure means reduced braking power — a serious safety hazard.
How long does an air spring last before it needs replacement?
Air springs typically last 5 to 10 years or 500,000 to 1 million miles, depending on driving conditions and maintenance. Rough roads, heavy loads, and poor maintenance shorten the lifespan. Regular tank draining and inspections help springs last toward the longer end of that range.
What's the difference between a Hendrickson suspension and other air suspensions?
Hendrickson is one brand among several air suspension manufacturers for commercial trucks. Other brands include Meritor and SAF-Holland. They work on the same principle — using air springs instead of steel coils — but have different designs, parts, and service networks. Knowing your truck's specific brand helps you find the right parts and technicians.
Can I replace a Hendrickson suspension with a different type?
It's possible but expensive and complex. Switching to a traditional spring suspension requires replacing the air springs, compressor, tank, and all air lines, plus modifying brake and steering systems that may rely on the air system. Most truck owners keep the original suspension type unless it's damaged beyond repair.
Does an air suspension need special tires or wheels?
No, the suspension type doesn't determine tire or wheel choice. However, air suspensions allow you to run lower tire pressures safely because the air springs absorb more shock, which can reduce tire wear and improve ride quality. Your truck's tire specifications are based on its weight capacity and intended use, not its suspension type.