Collection vehicles are in for rough duty. Their suspension and brake systems take real beatings—between wet heavy garbage, severe braking and frequent lifting, stopping, and going.

By Peter Hildebrandt

The suspension system provides a way to cushion the shock that the vehicle and its chassis experience as the tires travel over the road. Unlike early systems that were rigid, mechanical, steel leaf springs that did little to cushion the problems of the road, today’s suspensions can provide a smoother ride, improve traction, and reduce the vehicle’s weight.

The three types of large truck suspension systems—air, rubber, and mechanical—have been adapted by the various manufacturers to provide a great deal of selection on today’s market.

Although suspension may not be the first system considered when ordering a new truck, there are enough differences in suspensions to lead to research and questioning.

Operators, dealers, and repairmen from around the country share their views on the latest in suspension and brakes, and a few simple things to remember to prolong the life of your truck’s suspension.

Choosing Options in Suspension
A large manufacturer of trash disposal trucks, Leach Co., receives commercially available chasses from various truck manufacturers and mounts their truck bodies on chasses from nearly all manufacturers, including International Harvester, Mack Trucks, Freightliner, and others.

“When a municipality or trash-hauler is making a decision about their overall truck, they often look to put together a package based on convenience of service and longstanding reliability,” says Bob Oudenhoven, product manager with Leach Co.. “The haulers and municipalities will have their own favorite brand of chassis and refuse truck body. The choice of suspension gets folded into the decision on the chassis. I guess this is something that might be considered a little peculiar about this industry. Someone may think when you get a Leach garbage truck, you get the package. In the end the customer has the choice on the chassis and all the components that go with it.”

Oudenhoven finds more and more that air ride suspensions are being used in refuse hauling because of improving conditions at landfills. “Traditionally, when landfills weren’t packed solidly, there was an issue with debris such as wire and ropes pulling the air lines off the suspension systems.”

The off-road demand on garbage trucks has become less as landfill conditions have improved and more transfer stations are in use, according to Oudenhoven. “If you look at trends, landfills are becoming bigger and they also have a higher concentration of people working the compactors and other equipment so that the debris is leveled quickly. There is less of a need for trash trucks to have off-road capabilities in their suspension systems.”

Gerry Remus, vocational marketing manager with Hendrickson, makes the point that, due to the growing complexities of the new sophisticated equipment in refuse trucks, a more cushioned ride is becoming more of a necessity; the smoother the ride, the less expense from wear on all these new parts.

Hendrickson recently came out with a new product, PRIMAAX, an air-ride suspension designed for heavy applications such as refuse. This is the company’s first vocational air-ride suspension system. “The superior ride quality of PRIMAAX provides driver comfort and equipment protection while delivering excellent articulation, stability, and traction for off-road use,” says Remus.

The company’s new HAULMAAX system features a low-maintenance design including a reduced number of bushings that require less maintenance. “Increasing the ability to put more garbage on every run is something we have achieved with HAULMAAX,” says Remus. “For a refuse vehicle this is crucial; it may enable the operator to expand a route or reduce the number of overload tickets, improving operational efficiency of the vehicle.”

The quest for a smoother ride ended in the founding of Link Manufacturing in 1968. “Mr. Nebbelink started out as a truck driver and he was tired of getting his rear end beat while going down the road, so he invented this truck cab suspension system,” says Dale Puhrmann, director of sales and marketing with Link Manufacturing Ltd. “We have recently made a couple of interesting changes with the introduction of the DuraLift II. It uses a lift bag that is very easy to service and also remains parallel through the entire lift operation so we don’t get a lot of torquing on the bushings and arms.”

IMAGE: HENDRICKSON

The geometry of the system is such that the piston and cylinder stay parallel. “There is not the problem of crunching the one side of the air as the other side balloons out,” says Puhrmann. “The air bags, as a result, last a lot longer. This particular air bag literally sits on the assembly. It is one of the first times it has been used in this country in this application, and it is very easy to replace the air bag. All an operator has to do is pop the retaining pins out, and pull the unit apart, and replace it.”

The bags are made of a standard rubber compound used in all lift bags. “They are not rare. They have just never been used in this application before,” says Puhrmann.

Liftable suspensions generally have an issue with the lift cylinders and the lift bags not staying parallel and over a period of time, allowing air to escape. “Everyone out there is trying to get as close as possible to parallel with the air bags so there isn’t a maintenance issue with them,” says Puhrmann.

Puhrmann says Link manufactures nearly a third of the cab suspension systems made in North America, and that trucks now have these suspension systems for weight distribution. “There are areas where these systems are recognized as helping meet the various state DOT’s bridge laws, and states where they are not. In western Canada, for instance, you very seldom see a lift axle because they don’t recognize the auxiliary axles as load-carrying. Beyond that, some areas require steerable suspension while others allow non-steerable suspension, which is clearly tougher on asphalt paving. Unless they are forced to lift them, they will tear the asphalt up pretty bad.”

Ridewell Suspensions makes a unique mechanical suspension system for refuse trucks. Their OEM suspension system comes at a premium price. “Some of the reasons that end users are willing to pay that premium price up front is that there is almost no maintenance expense on this system, it is very durable, and requires little attention,” says Rick Rickman, Ridewell’s vice president of sales. “Our suspension performs well in service and is fully articulated. These factors make it well suited to a variety of terrains, including both off-road conditions and standard street settings.”

Rickman stresses that Ridewell’s rubber block-style suspension acts like an independent suspension. Each of the four corners of the tandem boogey has independent torque beams for superior articulation and traction. The fasteners should be checked to see if they are properly torqued. This check should be done first at approximately 6,000 miles, and thereafter each 50,000 miles that the vehicle is driven.

“New York City is one of our biggest customers for our suspension system,” says Rickman. “They feel that—despite a higher initial purchase price than other suspensions—the total lifecycle cost will be much lower. All vehicles in New York City’s trash collection fleet are outfitted with the Ridewell suspension system before they arrive for duty.”

Ridewell also manufactures air-ride suspensions for trash transfer trailers that are used to an increasing degree in the waste hauling industry. Maintenance requirements for these suspensions are the same as the mechanical truck suspensions previously mentioned: a torque check at 6,000 miles and every 50,000 miles thereafter. Additionally, the moving parts on all suspensions should be visually inspected every three months or so for any signs of interference, along with a check of welded and bolted connections to make sure they are secure.

IMAGE: SILENT DRIVE

Because of the growing demand for a system that will carry more GVW, Silent Drive has found a niche in supplying an additional axle on waste collection vehicles. “The weight laws are starting to crack down more and drivers are only able to carry so much weight on their truck,” says Reese Kelch, sales manager for Silent Drive. “But if they put more axles on they can carry more weight. We help spec out what they’re hauling, how they’re hauling it, and what they need to do to haul more waste without getting ticketed.”

Silent Drive provides air-suspension systems primarily for Class 6 to Class 8 trucks, with their biggest growth now in the Class 7 and 8 trucks. “We build about 28 different suspensions,” says Kelch. “But we also build about 280 different variations of suspension systems. We have a lot of resources to pool from when it comes to different trucks and different applications.”

Silent Drive’s system uses all urethane bushings, which makes their suspensions virtually maintenance-free, according to Kelch. “Just as an old eraser in your desk drawer will eventually become crumbly, rubber bushings on suspensions have the same problem. Urethane is so much more resistant to road grime, salt, and oils.”

The company offers a five-year warranty on their bushings, but recommends that all standard maintenance checks be run regularly on brakes, camshafts, and bushings. “There is no such thing as a maintenance-free truck,” says Kelch.

Timbren SES (Suspension Enhancement Systems) has a spring-assist system that works between the frame and the axle of light-duty trucks and SUVs, and between the frame and spring U-bolt pad of heavy-duty trucks. The aftermarket system acts as a stabilizer providing stability to vehicles, especially in high-center-of-gravity situations, thereby improving vehicle handling. The product is primarily for light- and heavy-duty trucks, with hundreds of units designed for both front and rear axles.

The system cushions road shocks and acts as a load leveler for heavily loaded vehicles, whether it is trucks operating at or beyond the capacity of the suspension or when towing heavy trailers. The heart of every Timbren SES kit is a hollow rubber spring, each of which has been designed for specific vehicles and applications.

“The popularity of this system is undoubtedly the result of both its simplicity and effectiveness,” says Parto Rezania, chief of engineering at Timbren. “They are very easy to install, need no maintenance, and are guaranteed to do the job as long as one owns the vehicle. Another advantage is that the system only kicks in when the vehicle is under load. At all other times the vehicle rides on its own suspension.”

Chalmers Suspensions manufactures suspensions for all the major OEM’s including Kenworth, Peterbilt, Freightliner, Mack, Volvo, and specialty truck chassis builders. “Our system is unique in that it is a rubber spring design that provides many advantages for the trucks of today,” says Livio Luchini, manager of sales administration at Chalmers. “Chalmers is very successful and well-received on trucks of all construction and vocational applications—including refuse-collection vehicles.

“The Chalmers system has lots of advantages and benefits, including improved traction; increased tire mileage; no leaf springs or air bags to replace; greatly increased stability and cornering; and full freedom of articulation, both parallel and diagonal, allowing vehicles to provide full traction and weight distribution on all types of terrain,” says Luchini. “It is one of the lightest suspensions in the industry but extremely rugged. It can definitely take a beating as well as protect the frame of the vehicle and mounted equipment by absorbing the road bounce and shock before it is transferred to the frame.”

Luchini says that this is basically a maintenance-free suspension. The design allows for ease of maintenance that can be accomplished in any shop without the use of special tools or presses or expensive equipment. “The Chalmers needs no greasing or oil ever, and all work is easy and simple to perform. This helps to eliminate costly parts and the ever-important costs of downtime.”

Service and Maintenance
Larry Theede, service manager of Truckaline Suspension Center of Blaine, MN, works on different truck suspensions on a daily basis. His largest workload is with the Class 8, heavy dump trucks, such as Mack. These suspensions are known as the “hockey puck” suspension because of the way their rubber discs look. Theede also works on nearly every other type of suspension on the market, from Freightliner air rides to Kenworth air glides to Peet air leafs.

Theede explains that the air-ride suspensions use an air bag on top of a spring to stabilize the vehicle and to cut down on the weight. Primary users of this type of suspension are road trucks, such as semi trucks that need to keep their weights down. Because they are not going off-road with their trucks, these suspensions are not heavy duty.

The waste collection industry relies heavily on the walking beam suspension, with a square, 50-inch-long beam with rubber steel-encased bushings on each end of the beam. On top of the beam is a heavy-duty leaf spring. In the case of the Chalmers suspension, this spring is solid rubber.

Another suspension growing in popularity for refuse collection vehicles is the “T-ride” or “sure-track” suspension. It is mostly used on Volvo trucks and uses a long leaf spring on the top, and on the bottom has rubber bushings on a beam. “The main maintenance job on any of the many suspensions that we service are the bushings,” says Theede. “When they wear, what happens is that the axles start walking side to side and then your truck is not running true down the road.”

Valley Truck and Trailer Service Inc. dba State Spring Services does a brisk business in the growing Phoenix area, repairing various truck suspension systems and brakes. President Chris Baroldy says the constant workload of the dirt-hauling trucks and cement mixers in the area means that many of these vehicles will end up at the repair shop. Waste trucks and roll-off trucks play an integral part in all this construction.

IMAGE: CHALMERS SUSPENSIONS

The company does no work on the lifting parts on the main bodies of waste collection trucks. Baroldy works on suspensions, engines, and drive trains in these vehicles. “With each type, it’s all about maintaining them properly—whether air ride, spring suspension, or walking beam. All trucks have front springs and they all have to get their pins greased. It should be done each time you lube the truck and change the oil.”

Baroldy says the main reason for spring failure and breakage is not maintaining proper U-bolt torque. “You need to check the torque within 200 miles of having those springs replaced in addition to inspecting them periodically from then on.”

Regarding two suspension products that he is familiar with, Baroldy adds, “Timbren’s system is a good product that definitely works in certain situations and Chalmers systems have become very popular in this area with all the recent increase in use of cement mixers.”

He also recommends that truckers in the waste-hauling or other industries adjust brakes on a weekly basis. “Regular inspections and replacement according to the DOT guidelines is the best way to go. There will be some chatter when the air brakes are wearing. This may be caused by dirt, too much heat building up, glazing, or worn bushings. A weekly visual inspection of brakes for cracks on the outside lining of the brakes or the lip of the drum for severe wear is important.”

Scott Kenoyer, fleet manager with the city of Augusta, ME, says their fleet’s single-axle garbage trucks were experiencing difficulties. “They have 18-yard bodies and when they are loaded they are overweight on the rear axle. Maine’s state laws specify that only 24,200 pounds can be carried on the rear axle. So in a few weeks I’ll be adding a Duramax ‘pusher’ axle—manufactured by Link Manufacturing—to the truck to take some of the weight off the rear axle.”

The city of Augusta does not haul garbage on Mondays, so on that day operators check all their collection vehicles’ suspension systems. This check includes ensuring that the lead springs are not cracked, checking the pins for proper greasing, and doing the greasing if required. “With our abundant potholes here in Maine, checking the suspension on our trucks is a must,” says Kenoyer. “They take quite a bit of abuse and then will break. We are also on the lookout for problems with the brakes before anything can happen down the road. But besides inspections and greasing of the springs there is really little that you do with suspension systems as far as maintenance.”

Dan Arnott, service manager at Michigan Truck Spring, a repair and sales facility for all Class 6 to Class 8 trucks in Saginaw, echoes many of the claims that Fernbach says about his company’s suspension system add-on. “We’ve had Timbren for five or six years now and it’s a very simple installation,” says Arnott. Most of the installations take no more than an hour and a half or two hours maximum, depending on which vehicle the system is going on. Once it is installed, it is pretty maintenance-free. I have seen them go beyond 100,000 miles in some vehicles. As long as the units don’t get oil-soaked, they hold up well. The company stands behind their product 100%, too.”

When it comes to brake maintenance on the many vehicles that Arnott works with in his company’s business, he has two words: monthly inspections. “Make sure that everything with the vehicle’s brakes is 100% each month and you’ll definitely save money on brake drums and other work you’ll have to do down the road.”

Your truck’s suspension may not be the system on your truck that is first in for repair work. It may not even be something that you know much about, until after you’re already an owner or operator of the vehicle. But suspensions do make a difference in the life of your truck’s chassis, body, and tires, as well as the spine of the operator.

Peter Hildebrandt writes extensively on engineering and scientific subjects.

MSW - September/October 2005