What Hendrickson Suspensions Do

Hendrickson is a manufacturer of suspension systems for trailers and heavy trucks, not a single product but a family of designs. Their suspensions connect the trailer frame to the axles and wheels, absorbing road shock and keeping the load stable during transport. The most common Hendrickson systems you'll encounter are air suspensions and spring-based suspensions, each built differently and maintained differently.

Hendrickson suspensions are standard equipment on many commercial trailers because they're engineered to handle repeated heavy loads and long highway miles. Understanding which type you have and what it needs is the first step to keeping it working and avoiding costly downtime.

Key Takeaways

  • Hendrickson makes both air suspensions and mechanical spring suspensions; air systems are smoother but require more maintenance, while spring systems are simpler but transmit more road shock.
  • Air suspensions need regular checks of air bags, valves, and compressors because a leak or failed component can cause uneven ride height and brake problems.
  • Spring suspensions require inspection of leaf springs, bushings, and U-bolts for cracks, corrosion, and looseness, which worsen quickly under load.
  • Both types need alignment checks when you notice uneven tire wear, pulling to one side, or after hitting a pothole or curb.
  • A suspension problem that feels minor — a slight bounce or lean — often signals a component failure that will get worse and damage other parts if ignored.

Air Suspension Systems: How They Work

Hendrickson air suspensions use pressurized air in rubber air bags to support the trailer's weight and absorb bumps. The system includes an air compressor (usually engine-driven), an air dryer to remove moisture, a series of valves that control air pressure, and the air bags themselves mounted between the frame and axles. When you load the trailer, the system automatically adjusts air pressure to keep the ride height level.

The advantage is a smooth ride that protects cargo and reduces driver fatigue. The disadvantage is complexity: more components mean more things that can leak, fail, or need adjustment. A single air bag leak, a stuck valve, or a failed compressor will throw the whole system out of balance.

You'll know an air suspension is failing when the trailer sits lower on one side than the other, bounces excessively after bumps, or makes hissing sounds when parked. These are signs that air is leaking or the system isn't holding pressure. Ignoring them leads to uneven tire wear, brake imbalance, and eventually frame damage from the trailer sagging unevenly.

Spring Suspension Systems: How They Work

Hendrickson spring suspensions use stacked metal leaf springs to support weight and absorb road shock. The springs are bolted to the trailer frame at one end and connected to the axle housing at the other, usually through a shackle that allows the spring to flex. Shock absorbers (dampers) are mounted alongside to control how much the springs bounce after a bump.

Spring systems are simpler and cheaper than air systems, with fewer components to fail. They don't require air pressure monitoring or compressor maintenance. The trade-off is a rougher ride — the springs transmit more road shock to the frame and cargo — and they wear faster under heavy loads because the metal fatigues with each flex.

Spring suspensions fail when leaf springs crack, when U-bolts (the bolts that clamp the springs to the axle) loosen, or when bushings (rubber or polyurethane sleeves that allow the spring to pivot) wear out. A cracked spring or loose U-bolt will cause the trailer to lean, bounce unevenly, or make clunking sounds over bumps. Unlike air systems, springs don't leak — they just break.

Maintenance Tasks for Air Suspensions

Check air bag condition every month or before long trips. Look for cracks, bulges, or signs of air leaking (a hissing sound or visible deflation). Air bags are rubber and wear out; most last three to five years depending on load and road conditions. A damaged air bag must be replaced — it cannot be repaired.

Inspect all air lines and fittings for leaks. Use soapy water sprayed on connections; bubbles mean air is escaping. Tighten loose fittings with a wrench, but if a line itself is cracked or pinhole-leaking, it needs replacement. A small leak will drain the system over hours or days, causing the trailer to sag.

Check the air dryer cartridge according to the manufacturer's schedule, usually every 12 to 24 months. The dryer removes moisture from compressed air; if it clogs or fails, water enters the system and corrodes internal components. A clogged dryer also reduces air pressure, which the system compensates for by running the compressor harder and using more fuel.

Listen for compressor noise and feel for unusual vibration. A compressor that runs constantly, makes grinding sounds, or gets hot is failing. Compressor replacement is expensive, so catching problems early matters. If the system won't hold pressure even after you've checked bags and lines, the compressor or a valve is likely the culprit.

Maintenance Tasks for Spring Suspensions

Inspect leaf springs for cracks every month, especially after rough roads or heavy loads. Look along the length of each spring for visible breaks in the metal. A cracked spring loses strength and can break completely under load, causing sudden sagging or even a wheel to shift position. Cracks start small and grow, so replace a cracked spring before it fails entirely.

Check U-bolts for tightness by trying to turn them with a wrench. Loose U-bolts allow the spring to shift on the axle, which causes clunking, uneven tire wear, and eventually spring breakage. Tighten them firmly but do not over-tighten, which can strip threads or crack the axle. If a U-bolt spins freely or the nut is missing, replace it when ready.

Examine bushings where the spring connects to the frame and shackle. Worn bushings look cracked, flattened, or missing chunks of rubber. They allow excessive movement, which causes clunking and accelerates spring wear. Bushing replacement requires removing the spring, so it's often done during other suspension work.

Inspect shock absorbers for leaking fluid or damage. A leaking shock absorber won't control spring bounce, which makes the trailer bounce excessively and tire contact uneven. Shocks typically last three to five years. If the trailer bounces more than once after a bump, the shocks are worn.

When to Get Professional Alignment and Inspection

Bring the trailer to a suspension specialist if you notice uneven tire wear (one side wearing faster than the other), the trailer pulling to one side while towing, or a noticeable lean when parked. These are signs of misalignment or suspension damage that a visual inspection alone won't catch. A professional alignment uses specialized equipment to measure axle angle and frame geometry.

After hitting a pothole, curb, or debris on the road, have the suspension checked even if nothing looks obviously broken. Impact damage can bend axles, crack welds, or damage components internally. Catching it early prevents cascading failures that damage tires, brakes, and the frame.

A full suspension inspection — checking all components, measuring ride height, and testing air pressure or spring condition — takes one to two hours and costs less than replacing a damaged axle or frame. Many shops include this with routine maintenance or tire service.

Common Suspension Problems and What They Mean

A trailer that sits lower on one side than the other usually means an air bag is leaking (air suspension) or a spring is cracked (spring suspension). Do not drive far — the uneven load distribution stresses the frame and axles. Have it towed to a shop or park it until repaired.

Excessive bouncing after bumps signals worn shock absorbers or, in air systems, a valve that isn't damping properly. The trailer will feel unstable and cargo can shift. Shocks are a straightforward replacement.

Clunking or rattling sounds over bumps usually come from loose U-bolts, worn bushings, or a cracked spring. The sound gets worse as the component deteriorates. Tighten or replace the loose part before it breaks completely.

A hissing sound when the trailer is parked (air suspension only) means the system is leaking air. The trailer will sag over hours. Find and repair the leak before the next trip.

Frequently Asked Questions

How often should I inspect my Hendrickson suspension?

Check air bags, springs, and bolts monthly or before long trips. Have a full professional inspection once a year or every 50,000 miles, whichever comes first. If you haul heavy loads regularly or on rough roads, inspect more often.

Can I drive with a leaking air bag?

Not safely. A leaking air bag will deflate over hours, causing the trailer to sag and the brakes to work unevenly. The uneven load damages tires and the frame. Have it repaired before the next trip.

What's the difference between Hendrickson air and spring suspensions in terms of cost?

Spring suspensions cost less to buy and simpler to maintain, but wear faster under heavy loads. Air suspensions cost more upfront and need regular compressor and dryer maintenance, but provide a smoother ride and last longer if maintained. Total cost over the trailer's life depends on how much you haul and how far.

Why does my trailer lean to one side when parked?

In an air suspension, one air bag is leaking or the system isn't holding pressure. In a spring suspension, a spring is cracked or a U-bolt is loose. Both require repair — do not ignore it, as the lean worsens and damages other components.

Do I need to replace the whole suspension if one component fails?

No. Individual components — air bags, springs, U-bolts, shock absorbers, compressors — can be replaced separately. A shop can diagnose which part is failing and replace only that part. Full suspension replacement is rare and usually only done if the frame is damaged.