Fresh Air

Today’s equipment market may be soft, but trailer suspension manufacturers have been busy. We actually have an entirely new entrant in the field-Dana Corp.’s Heavy Truck Group-plus a second product from ArvinMeritor. A couple of seasoned trailer-suspension veterans, Hendrickson and ReycoGranning, also have been working hard.

Not surprisingly, the emphasis has been on air-ride. There are about a million air-ride equipped trailers on the road now, and by 2005 the experts say more than 70% of new trailers will be spec’d that way. Here’s a look at the latest from air-ride trailer suspension manufacturers.

ARVINMERITOR

ArvinMeritor has been growing its trailer suspension family-and changing its name. The company’s second trailer air suspension-a single axle/fabricated design for specialized vocational trailers-is called the FS Series. It joins the lightweight RHP Series introduced four years ago in the family of RideStar Suspension Systems, the new name for the company’s suspension product line. Some 50,000 RHP highway-van suspensions have been sold so far.

The RideStar FS Series was designed for trailers in specialized vocational markets such as flatbeds, tankers, auto haulers, and lowboys. Field and lab testing will be finished soon, with production and sales starting this Fall. First off the mark will be the FS230 Top Mount model.

Engineers were given pretty free rein, by all accounts, aiming for a driver-friendly design needing minimal maintenance. They came up with a “revolutionary” new bushing design. The patent-pending FS bushing uses interleaf shims for superior fore/aft stiffness compared to other single-bushing designs, the company says, while the more narrow design saves on total suspension system weight and bulk.

The engineers were also able to take advantage of shock absorber experience at ArvinMeritor’s Ride Control business, which makes Gabriel shocks. Borrowing from European technology, the shock absorbers were specially developed to work with the FS suspension geometry, “delivering exceptional damping characteristics and an innovative integral check-strap,” ArvinMeritor says. Increased damping force should mean less fatigue damage, plus better braking and longer tire life.

Shock absorbers on the FS are covered by a three-year warranty, while the suspension at large is covered for five years/500,000 miles.

DANA

Dana’s new Ride & Control Systems Division used the Mid-America Truck Show in Louisville, Ky., to introduce its first integrated trailer suspension module-the AdVANtage air-ride model. With tandem weight capacity ratings from 36,000 to 46,000 pounds, it was designed specifically for vans and refrigerated trailers where a soft ride and cargo protection are valued.

“The suspension has been configured to incorporate several of the ‘intelligent’ product offerings our Advanced Chassis engineers have developed that are common in both tractor and trailer applications,” says Greg DiMarco, general manager, Ride & Control Systems. “This is the first in a series of modules that Dana will be offering to the commercial vehicle industry.”

The AdVANtage trailer air-ride suspension features “EZ-Pull” technology that improves performance and reduces maintenance; a ride-height lock mechanism to “eliminate” dock walk; and a rigid axle-to-beam connection to improve alignment and cut maintenance. The 146mm axle tube is designed to provide greater strength at reduced weight, and larger pivot bushings should yield greater durability, longer life, and less need for maintenance. Single or double-anchor-pin brakes provide parts commonality between tractor and trailer.

Options include the Spicer LMS Hub System, which can significantly reduce wheel-seal failures while eliminating the need for wheel-bearing adjustment. As well, there’s the Tire Maintenance System to keep tires at recommended pressure levels and Eaton antilock braking products.

REYCOGRANNING

The new ReycoGranning model 19AR/RS1062 is an air-ride van slider suspension system rated at 19,000 pounds capacity per axle. It’s claimed to be currently the lightest air-ride slider on the market, at just 854 pounds.

Weight is saved, but strength not compromised, by using narrow beams and hangers, only two main crossmembers, and by eliminating u-bolts in the axle attachments. Strength has been added via a new unitized hanger design which attaches the hangers to the sides of the rails, not just at the bottom of the rails. Hangers and rails are joined by plug welds to reduce stress risers.

Also adding strength are nine-inch seven-gauge side rails, industry-standard double convoluted air springs, and 4.5-inch wide bushings. Options include a bolt-on load block mechanism, bolt-on mud flap brackets, choice of axle type, multiple pin spacings, and quick pin release. The ReyAlign one-man axle alignment feature is standard.

HENDRICKSON

Hendrickson International’s INTRAAX 300 trailer suspension recently began rolling off production lines. It’s the industry’s first integrated 30,000-pound suspension/axle system, aimed at forestry, mining, off-road, and other severe-service applications. Offered in both top-mount and low-ride-height/liftable configurations, it offers ride heights from nine to 19 inches.

The robust AA300EDT (extreme-duty top-mount) and AA300EDL (extreme-duty low-ride-height/liftable) are full 30,000-pound structural- and axle-capacity systems. They feature low-pressure air springs with steel pistons and full bottom-plate coverage; high-damping, extended-service shock absorbers; and a 30,000-pound capacity axle with HP spindles. Options include rear-mount shock absorbers and chain down-stops.

For more mainstream heavy hauling, the INTRAAX AA300T and AA300L provide a 30,000-pound suspension capacity matched with a full 25,000-pound axle rating. They share many features and options with the extreme-duty models. HN and HP spindles are available for both the top-mount and low-ride units.

The INTRAAX 300 systems team with Hendrickson’s Under Beam Lift (UBL) to give operators a liftable suspension for heavy-duty applications like dumps, tankers, straight- and drop-deck platforms, loggers, chip haulers, and specialty trailers.

SIDEBAR: Hutchens Drops 360-00 Springs

Hutchens Industries no longer recommends the 360-00 high-arch single-leaf spring for use in its suspension systems because it “contributes heavily to premature wear and failure of certain suspension components, and the problem has worsened as trailers and chassis have grown longer and heavier.”

Alternatives include the 324-01 two-leaf spring, the 354-00 three-leaf spring, or, perhaps the 363-00 low-arch single-leaf spring. For more information, contact the Hutchens engineering or customer service departments at 1-800/654-8824.

SIDEBAR: Hot Shocks

Shock absorbers should be hot after they’ve worked awhile, anything up to about 350 degrees F. That’s because they literally absorb the energy produced by the sprung vehicle and convert it into heat. So after normal use they should be at least warm to the touch, and possibly hot. If they’re cool, you’ve got a problem.

ArvinMeritor suggests this simple test: operate the vehicle at moderate speeds for about 15 minutes, then stop and carefully touch each shock absorber on its body below the dust cover or tube. (First, get a reference ambient temperature from a nearby chassis component).

All shocks should be warmer than the chassis. Look especially for a shock that’s noticeably cooler than its counterpart on the other end of the axle. These shocks should be removed and examined further.

To inspect for an internal failure, remove the suspect shock and shake it. Loose or rattling parts likely indicate an internal failure.