What Hendrickson suspension does for your trailer
Hendrickson makes suspension systems that connect your trailer's axles to its frame and absorb the shock of bumps, potholes, and uneven road surfaces. The suspension keeps your load stable, reduces wear on your cargo and tires, and makes the trailer easier to steer and brake. Most commercial trailers use one of Hendrickson's three main types: air suspension, spring suspension, or a combination of both.
The suspension you choose affects how your trailer handles different loads, road conditions, and weather. Air suspension is smoother and adjusts automatically to weight changes. Spring suspension is simpler, costs less upfront, and requires less maintenance. Combination systems try to balance both benefits. Understanding which type you have helps you know what maintenance it needs and when replacement parts become necessary.
Key Takeaways
- Hendrickson suspension systems absorb road shock and keep loads stable, with three main types: air, spring, or combination systems.
- Air suspension automatically adjusts to weight changes and provides a smoother ride but requires more maintenance than spring systems.
- Spring suspension is simpler and cheaper but does not adjust to load changes and wears faster under heavy use.
- Replacement timing depends on your suspension type, how much weight you carry, and road conditions where you operate.
- Regular inspection of air bags, springs, bushings, and shock absorbers can catch wear before it causes brake or steering problems.
Air suspension: how it works and what wears out
Hendrickson air suspension uses rubber air bags (also called bellows) filled with compressed air to support your trailer's weight. As the load changes, an automatic leveling valve adjusts the air pressure inside the bags to keep the trailer at the same height. This keeps your cargo level and prevents the trailer from sagging or bouncing.
The main parts that wear out are the air bags themselves, the air lines and fittings, and the leveling valve. Air bags typically last three to five years depending on road conditions and how much weight you carry. Cracks, leaks, or bulging in an air bag mean it needs replacement. Air lines can crack or separate from fittings, causing slow leaks that make the suspension sag. A failing leveling valve will not adjust pressure correctly, so the trailer rides too high or too low.
Air suspension also includes shock absorbers that dampen bouncing after bumps. These wear out gradually and are harder to notice than a leaking air bag, but a worn shock makes the trailer bounce longer and reduces stability. Many operators replace shocks at the same time they replace air bags to avoid a second service call.
Spring suspension: simpler design, different maintenance needs
Hendrickson spring suspension uses steel leaf springs or coil springs to support the load and absorb bumps. Springs do not adjust to weight changes the way air bags do, so a heavily loaded trailer sits lower than a lightly loaded one. This is normal and does not mean the suspension is failing.
The main wear points are the springs themselves, the bushings (rubber or polyurethane pieces that connect springs to the frame), and the shock absorbers. Leaf springs can crack or lose their curve over time, especially if you regularly carry maximum weight or drive on rough roads. A cracked spring reduces load capacity and makes the trailer unstable. Bushings wear out faster than springs and cause clunking noises or excessive movement when they fail.
Spring suspension generally lasts longer than air suspension before needing replacement—often five to seven years or more—because there are fewer moving parts and no air pressure to maintain. However, springs are heavier than air bags and can make the trailer ride rougher, especially when empty or lightly loaded.
Combination systems and when to use each type
Some Hendrickson trailers use a combination of air suspension in the front and spring suspension in the rear, or vice versa. This setup tries to balance the smooth ride of air suspension with the durability and lower cost of springs. Combination systems are common on trailers that carry variable loads or operate in mixed conditions.
Choose air suspension if you carry heavy or delicate cargo that needs a smooth ride, operate in urban areas with frequent stops and starts, or want automatic load leveling. Choose spring suspension if you want lower upfront cost, operate mainly on highways with consistent loads, or prefer simpler maintenance. Combination systems work well if you need both smooth handling and durability but can afford moderate maintenance on the air side.
Signs your Hendrickson suspension needs replacement
Watch for these warning signs that your suspension is wearing out. A sagging trailer that does not level itself (on air suspension) or sits noticeably lower on one side suggests air bag or spring failure. Excessive bouncing after bumps or a rough, harsh ride means shocks are worn. Clunking or creaking noises when turning or braking point to failing bushings or loose connections.
Uneven tire wear—more wear on the inside or outside edge of tires—often comes from suspension problems that throw the wheels out of alignment. Brake problems like pulling to one side or longer stopping distances can result from a sagging suspension that changes brake geometry. If your trailer pulls or drifts to one side while driving straight, suspension wear may be affecting steering response.
Air suspension systems may show visible leaks: oil or fluid around air bags, hissing sounds when the engine is off, or a compressor that runs constantly. Spring suspension may show cracks in the springs themselves, visible rust or corrosion, or metal-on-metal contact where bushings have worn away.
Maintenance to extend suspension life
Regular inspection catches problems early and prevents expensive failures. Check air bags monthly for cracks, bulges, or leaks. Look at air lines and fittings for loose connections or damage. Listen for hissing that suggests a slow leak. On spring suspension, inspect springs for cracks and bushings for wear or movement.
Keep your trailer at the correct tire pressure—underinflated tires force the suspension to work harder and wear faster. Avoid overloading beyond the trailer's rated capacity, which accelerates wear on all suspension components. Drive smoothly when possible; hard braking, sharp turns, and rough roads all increase suspension stress.
Have a professional inspect your suspension annually or every 50,000 miles, whichever comes first. They can measure air bag condition, check spring curve, test shock absorber function, and spot wear on bushings before it becomes dangerous. Replacing worn components early is cheaper than waiting for a failure that damages other parts or strands you on the road.
Replacement parts and when to do it yourself versus hiring a shop
Hendrickson suspension parts are available from trailer dealers, online suppliers, and independent shops. Air bags, springs, shocks, and bushings are all replaceable components. Prices vary widely depending on the part, your trailer model, and where you buy. Air bags typically cost $200 to $500 each; springs $300 to $800; shocks $150 to $400.
Some operators replace their own suspension parts if they have mechanical experience and the right tools. Air bag replacement requires disconnecting air lines and unbolting the old bag, then installing the new one and reconnecting lines—straightforward but requires care to avoid damaging fittings. Spring replacement is more labor-intensive because springs are under tension and require special equipment to remove safely.
Most trailers benefit from professional replacement because suspension work affects braking, steering, and load stability. A shop can also inspect related components like brake lines, wheel bearings, and frame damage while the suspension is apart. If you are unsure whether a component has failed or is straightforward worn, a professional inspection costs less than guessing wrong and replacing the wrong part.
Frequently Asked Questions
How do I know if my air suspension is leaking?
Listen for a hissing sound when the engine is off, especially near the wheels. Check around air bags and fittings for oil or moisture. On some systems, the compressor runs constantly or the trailer sags noticeably after sitting overnight. A slow leak may not be obvious until you load the trailer and notice it sits lower than usual.
Can I drive on a cracked spring?
You can drive short distances on a cracked spring, but it is not safe for long trips. A cracked spring reduces load capacity and makes the trailer unstable, especially during braking or turning. The remaining springs have to carry extra weight, which accelerates their wear. Have it replaced before the next loaded trip.
What is the difference between a shock absorber and a spring?
Springs support the weight and absorb the initial bump. Shocks dampen the bouncing that happens after the bump, so the trailer settles quickly instead of bouncing up and down. Both wear out independently—a worn shock does not mean the springs are failing, and vice versa.
Do I need to replace all four air bags at once?
If one air bag has failed, the others are likely near the end of their life too. Replacing all four at once prevents a second failure a few months later and ensures even load support. If only one is leaking and the others look good, you can replace just that one, but plan to replace the rest within the next service cycle.
How much does a full suspension replacement cost?
Cost depends on whether you have air or spring suspension and how many components need replacement. Replacing all four air bags, lines, and a leveling valve typically runs $2,000 to $4,000 in labor and parts. A full spring suspension replacement with new springs, bushings, and shocks may cost $1,500 to $3,000. Get quotes from two or three shops before deciding.