Maximum payload. Minimum road damage. Trucking is a lot more complicated than just this pair of often-conflicting goals, but when it comes to today’s spec’ing environment of multiple axles and wide-spread suspensions to handle heavy loads, here, at least, there’s a solution at hand.

While traditional “rigid” lift axles have been around a long time, they’re not very popular with enforcement authorities and politicians (read: they’re forbidden in many jurisdictions) because of two physical facts of life. If a driver leaves the lift down on the roadway during a sharp turn, he’ll likely incur “tire scrub,” which damages both the tread on that axle’s tires and the pavement surface at the intersection, as well as encountering stiff steering-wheel response. Lift the axle to help make the corner, and he risks imposing excessive and illegal weights on-and through-his remaining axles.

Bad for the vehicle. Bad for the road surface. And bad for the chequebook if an enforcement officer happens to be watching.

Another factor contributing to restrictions on lift axles are provincial and U.S. bridge formulas, sets of tables that define allowable maximum weights on different axle combinations and spreads to ensure that highway bridges in particular are not over-stressed by loaded commercial vehicles. Enforcement officials are increasingly cracking down on axle-overweight violations that contravene bridge laws.

Self-steering axles or SSAs-widely popular in Europe for decades and becoming more so in North America-can solve all these problems. Incorporating either a traditional I-beam steer axle or a fabricated square-tube leading-kingpin design, a self-steering auxiliary suspension follows the direction of vehicle travel (straight truck or semi-trailer) with minimal resistance to side forces.

Typically equipped with oversize “Super-Single” tires rather than dual wheels-which would tend to inhibit the self-steering function due to their more limited turning radius-these suspensions let their wheels align with the vehicle’s direction of movement thanks to simple road friction. Most designs allow 20 degrees of turn, and weight ratings range from a standard 13,200 pounds to as high as 25,000 pounds (configurations above 20,000 pounds do require dual wheels, and are much less frequently seen). Used in both “pusher” and “tag” locations, the majority of SSA suspensions are liftable, a feature only intended for use when running empty.

One industry observer estimates that currently about 90% of the lift-axle market (rigid and self-steering) is accounted for by vocational straight trucks like dumps, refuse haulers, and concrete mixers, while the other 10% comes from semi-trailers.

“We’ve been seeing 25% to 30% annual growth recently in our lift-axle business, which includes both rigid and self-steer models,” says Richard Rickman, director of sales at Texas-based Watson & Chalin Manufacturing. “The self-steer segment is increasing at a more rapid pace, though, and I’d say now comprises about 60% of all lift-axle sales in North America.”

Acknowledging that self-steer units cost upwards of 20% more than rigid lift models, Rickman notes that there’s a significant payback in lower tire wear-and not just on the SSA wheel ends, either.

“You’ll get three to four times the tire life on a steerable lift than with a rigid,” he says, “but there’s a wear savings on your steer-axle tires, too. We feel the payback period on this additional investment is generally less than two years. And don’t forget the benefit of avoiding fines and citations for axle-overweight situations.”

Watson & Chalin is one of several firms that market entire self-steering axle suspension systems. Others include Henderson Auxiliary Axle Systems, of Hebron, Ohio; Silent Drive Inc., Orange City, Iowa; Link HiSteer, Sioux Centre, Iowa; Hi-Steer Canada Ltd. (no longer affiliated with the similarly named U.S. operation) of London, Ont.; and Reyco/Granning, of Springfield, Mo., and Stoney Creek, Ont.

Additional companies make customized axles for SSA systems, and among these are KGI Industries, Oroville, Wash., and Canada’s own IMT Corp., formerly Ingersoll Machine and Tool, of Ingersoll, Ont.

(Component heavyweight Meritor Automotive was briefly in the lift-axle/SSA business following its takeover of Ohio-based Suspensions Inc., but ceased production in March in order to focus more on trailer air suspensions. Arrangements have been made to ensure aftermarket support to the Suspensions Inc. lift-axle customer base, however.)

“We produce more than 2000 axles for self-steering assemblies per year, and about 75% of our current production is exported,” says Jules Guillemette, project manager/axles, at IMT. “Our clients include Watson & Chalin, Silent Drive, and other firms.”

In most cases, the steering mechanism only works when the vehicle is moving forward; many SSAs use a locking mechanism to allow reverse-direction travel. However, suspension specialist Hendrickson recently added an axle that offers full self-steering during both forward and reverse movement. “Often, a self-steering axle has to be lifted when you back up, or the change in wheel caster will cock the wheels one way or the other,” says marketing manager Tim DeCesaro. “We recently introduced the ‘ParaRev’ model to our Ultra line of parallelogram-style auxiliary lift-axle suspensions, and this unit features an automatic shift mechanism that allows fore-and-aft axle movement and full self-steering in both directions. As a result, the axle can remain on the ground when the vehicle is reversing.”

At a rated capacity of 13,200 pounds, the ParaRev provides 13 inches of axle travel and a 25-degree wheel cut, and is usable in both pusher and tag locations.

NEW RULES

Despite some of the obvious benefits of SSAs, the trucking industry has been slow to adopt them. That may change soon, thanks to some recent provincial government moves in Canada. Both Quebec and Ontario have either passed or are considering regulations that mandate self-steering axles in certain circumstances on newly acquired semi-trailers.

In Ontario, the Ministry of Transportation announced plans to allow quad axles on 53-foot trailers-a tridem axle led by a single SSA. There are distinct conditions for their use: the single axle must be between 2.5 and 3.0 metres ahead of the lead tridem axle; be capable of turning 20 degrees in either direction; have only single wheels; the lift control must be on the trailer, not inside the tractor cab; and all four axles must carry equal loads.

The allowable weight is consistent with current rules governing one-three quads on 48-foot trailers: 32,000 kg when the tridem spread is from 3.0 to 3.6 metres, and 34,400 kg when the spread is between 3.6 and 3.7 metres.

The configuration will be allowed by permit (which cost $300 each), with fleets having to meet certain safety requirements in order to obtain them.

The drawback, of course, is that the 53-foot quad is restricted to Ontario.

But Quebec, which currently does not allow lift axles on semi-trailers longer than 15.5 metres (50 feet, 10 inches), is expected to begin an 18-month test of the safety and impact of self-steering axles-with single tires-this month.

Central to government concerns about rigid lift axles is the temptation for the driver to flip up that toggle on the dash while he’s under way. Some drivers either forget to drop the axle after a turn, or intentionally leave it raised even while heavily loaded because they believe the reduced tire friction will save fuel and allow a higher top speed on the highway.

These regulatory mandates that discourage the use of rigid lifts already are boosting interest in SSAs on new equipment orders, Guillemette feels.

“Self-steering axles can contribute their benefits even when retrofitted to existing vehicles,” he says, “but we feel the impact is maximized when the axle is spec’d as an integral part of the new-vehicle order. These Ontario and Quebec initiatives will encourage fleets to ‘think self-steer’ as they go through a full purchasing cycle.”

Indeed, one of the market trends Hendrickson marketing manager Tim DeCesaro has noted recently is that truck manufacturers are becoming increasingly involved in steerable lift-axle installation as part of the new vehicle’s customer spec.

“A lot of truck operators are indicating that they’re more comfortable having an SSA installed by the OEM instead in the aftermarket,” he observes. “It’s not that bodybuilders can’t do a good job, but there’s a perception among end-users that the original manufacturer can provide a better job by engineering the self-steering suspension(s) right into the truck on the production line.”

ACCEPTANCE STILL LOW

And how are SSAs viewed from the perspective of a vehicle retailer? At Kitchener, Ont.-based Breadner Trailer Sales, vice-president of sales Craig Sterling reports that self-steering axles traditionally haven’t been a significant concern of the customers who buy the 6000-plus new trailers Breadner sells annually. But that may be changing.

“I doubt we’ve had even a half-dozen customers who spec’d self-steer axles over the years,” he says. “But these recent moves by the Ontario government, in particular, are making us think that this may change things in the future.

“As a result, we’ve just started an in-depth evaluation of SSAs, working with our trailermakers to put together a database of who makes what, and which configurations are recommended for what type of trailer. That way we’ll be able to better serve clients who decide to incorporate self-steers.” While it’s true that SSAs have a long way to go before they become the norm, they’ve come a long way from their obscure beginnings.

In researching this article, we came upon an interesting assertion as who was the “father” of the self-steering axle-at least in the North American market.

“In early 1998, Link Manufacturing purchased the assets of H.S. Industries, of Sturtevant, Wisc.,” Dennis Tooker, division manager at Iowa-based Link, explains, “and that has become our HiSteer division.

“Well, the onetime owner of H.S., Dennis Lange, developed and patented the very first steerable lift axle back in the late 1970s. For years, Lange had been repairing rigid lift axles and the frames on which they were mounted, and he concluded that there had to be a better way to accommodate extra loads.

“His steerable innovation took a while to catch on, but it worked so well that other players in the industry started offering similar products, too.”

And the rest, you might say, is track ‘n’ roll.