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Riding on air

KALAMAZOO, Mich. - There's been plenty of discussion about NHTSA's desire to reduce tractor-trailer stopping distances, but very little has been said about the impact larger front brakes will have on...

KALAMAZOO, Mich. – There’s been plenty of discussion about NHTSA’s desire to reduce tractor-trailer stopping distances, but very little has been said about the impact larger front brakes will have on the suspension.

The proposed regulation to reduce stopping distances by 30 per cent likely means fleets will be specifying larger drum brakes on the front axles. It’s less expensive than slapping disc brakes on the entire unit and all indications are that the impending regulation can be met that way.

Dana officials, however, have expressed concern that the additional torque loads may impact the ride and handling of traditional front suspensions. Its answer: The new Dana Spicer FrontRunner air ride front suspension.

While front air suspensions are available today, they have been greeted with mixed reviews.

Dana says it has gone to great lengths to assure customer concerns with competitive products have been addressed in the FrontRunner.

The proprietary design includes a traditional taper leaf spring arrangement in combination with air springs as well as a roll control device. Collectively, Dana officials say the suspension system delivers improved driver control, handling and stability while improving overall ride comfort.

“Long haul drivers operating a truck equipped with these new suspensions will immediately identify the differences over front air suspensions available today,” vows Mark Davis, product manager, steer axles for Dana. “That’s because the FrontRunner gives a solid feel and response through the steering wheel. Straight line tracking also is excellent.”

When the new stopping distance regulations come into play, it’s expected that brake dive (the front end’s tendency to lower under heavy braking) will be a point of concern.

Davis says the FrontRunner’s variable rate air spring assembly will resist large front-of-vehicle suspension deflections during heavy braking.

Meanwhile, he says the suspension boasts lateral stability that is 2.5 times stiffer than competitive front air suspensions.

It all adds up to a better ride, not only while travelling at highway speeds but also when standing on the brakes or carrying out a sudden panic maneuver such as a lane change, Davis explains.

“We see these (NHTSA) regulations eventually dictating the use of larger torque steer axle brakes,” says Davis.

“The design of the FrontRunner suspension has taken this into account and already accommodates these brakes through the use of new brake reaction links and a variable rate air spring assembly.”

Davis goes on to say that drivers and fleet managers may be in for a rude awakening if they think larger front brakes won’t impact the performance of their current suspensions.

“The whole subject and issue of what to do with the suspension has lagged and we want to make sure the market knows there is a need for this suspension, otherwise fleets will be surprised when they learn their suspension doesn’t ride as well as it used too or is heavier than it used to be,” Davis warns.

The FrontRunner is 75 lbs lighter than traditional front suspensions and engineers say it’s possible to make it lighter yet.

“Weight reductions, of course, will translate to fuel savings and increased payloads,” Davis points out.

The first FrontRunners have been designed for use with linehaul trucks with long sleepers – most notably, the International 9000-series and Pete 387. Dana hasn’t ruled out extending the offering to other applications in the future.

Truck West recently had the chance to test two similarly spec’d International 9400s – one with a traditional suspension and one with the new FrontRunner.

Our route took us over some bumpy roads and a stretch of highway near Marshal, Mich.

The difference between the two trucks was immediately noticeable as we crossed a series of bumps en route to the Interstate. It was also evident when we dropped the right tires onto the rumble strips along the highway.

However, where the FrontRunner really stood out from its traditional counterpart was during a series of maneuvers we carried out on Dana’s test track. The maneuvers we performed included: a slalom run; a panic lane change; and a panic stop.

The improved lateral stability of the FrontRunner was evident from the passenger seat of the truck as well as from the outside. During the panic stop, the brake dive was minimal – in fact, it’s hardly fair to call it a dive at all (maybe a bellyflop).

The FrontRunner is clearly able to deliver on its promise to provide an improved ride and better performance during sudden maneuvers, but it will come at a premium price.

Davis said the cost will be “slightly more” than current offerings, but the difference could well be recouped over time thanks to the weight savings.

Davis also adds “Due to the high level of satisfaction and confidence the FrontRunner provides, we see this new product rapidly becoming a contributor to retaining drivers, broadening a fleet’s appeal in recruiting new drivers as well as providing a comprehensive solution toward reducing driver fatigue.”

The FrontRunner is easily-interchangeable with existing spring suspensions, Davis says, making for an easy transition for OEMs. With Bendix brakes on the axle, the entire module is available with one point of contact thanks to the relationship Bendix and Dana share with Roadranger.

The FrontRunner is currently undergoing field testing and it is slated for limited quantity release in April, 2006. Full production status will be reached in the fall of 2006, Dana representatives claim. n


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