TORONTO, Ont. - As clichd as this may sound, there's a lot riding on your equipment - and it's all bouncing along on the mechanical leaf springs, air bags or rubber blocks that create the all-important buffer between you and the next pothole.
December 1, 2004
John G. Smith, Technical Correspondent
SMOOTH OPERATOR: Maintaining your suspension can help reduce the risk of failures while providing improved ride quality.
SLOW DOWN: When travelling over rough surfaces, slow down. The suspension can be damaged by driving too quickly over potholes or other rough spots.
TORONTO, Ont. – As clichd as this may sound, there’s a lot riding on your equipment – and it’s all bouncing along on the mechanical leaf springs, air bags or rubber blocks that create the all-important buffer between you and the next pothole.
But as robust as they appear, suspension systems still require routine maintenance to lessen the vibrations that can weaken everything from wiring connections and bulb filaments to the welds that hold steel on steel.
Luckily, some minor maintenance procedures can offer some cheap insurance against major repairs.
1. Inspect suspension bushings at every oil change
Bushings can be cheap – particularly when you compare them to the cost of neglect.
Benson Truck and Trailer service manager Claude Seguin, for example, refers to a flatbed that was delivered to his Cornwall, Ont. shop once the driver began to notice a noise whenever he hit the brakes.
Two months ago, the truck’s worn bushings could have been replaced for about $200.
But they were left unchecked. Today, the bushings account for the cheapest line item on an invoice that includes brackets worth $250 per side, and a beam bushing that’s valued at another $1,200.
“If he had a good maintenance program, he’d get the shop to check the bushings when he gets the oil changed,” Seguin said.
Keep in mind that the life of the bushings can vary from one model of suspension to another, but trailer suspensions with longer wheelbases (between 72 and 100 inches) face additional stress, he added.
“You’ll gain one to two years (of life) with a short wheelbase.”
2. Re-torque the U-bolts
The U-bolts that hold various suspension components in place can loosen after an initial installation.
That means the related torques should be re-inspected after the first 5,000 km, said John Kozier, a suspension technician at Parts for Trucks in Halifax.
But your follow-up inspections don’t need to involve a torque wrench.
A well-torqued U-bolt will sound with “quite a nice ring” when hit with a hammer, Kozier said. In comparison, loose U-bolts will respond with a dull thud.
And if the loose fasteners aren’t re-tightened, you can expect to experience a vibrating driveline.
“Eighty-five per cent of the time, the U-bolts have shifted. Then the driveline will shift into a different position,” he said.
3. Stay true to the original spec’s
The spec’ing software used to outline every aspect of a new truck will typically ensure that a suspension system matches its approved application.
“I think consumers are probably more educated now than they’ve ever been, and a lot of that is because salesmen are more educated,” said Rick Wiebe, service manager at Fort Garry Industries in Winnipeg.
But all bets are off if the equipment is suddenly switched to a different use, and an unusual number of suspension repairs may be a sign that components are being asked to absorb bigger shocks than they were ever expected to experience. A suspension designed for over-the-road trips, for example, may only be allowed to travel off road 20 per cent of the time, and that’s well beyond the realities faced by many cement trucks or oilfield applications, he said.
4. Change the air bag pedestals
While air bags are relatively cheap to replace, it’s also important to inspect the pedestals on which they sit, since they can deteriorate over time.
Thank the all-corroding effects of road salt.
“Once the rust goes between (the bag and its pedestal), it starts separating the two pieces, pushing the plate up,” said Wayne Bellefontaine of Parts for Trucks in Halifax. “It’s not going to sit properly.
Still, some fleets have extended the life of the components beyond the typical five to eight years by applying a rust-inhibiting undercoating to their vehicles, he added.
5. Replace shocks as required
A vehicle’s shocks will play an important role in protecting everything from air bags to bushings, but many equipment owners fail to change them when they should – at the first sign of a fluid leak, Seguin said.
Simply remove the shock’s bottom bolt, and extend the component as far as possible if you want to have a good look.
6. Clear the air
If your equipment is riding on air bags, it seems obvious to suggest that it’s important to ensure the air supply is free of contaminants, but Wiebe said air dryers are often neglected.
“The desiccant should be changed annually, depending on the (operating) environment,” he said. “If you have moisture in the system, it’s going to freeze up.”
And the most common response to this problem can lead to further headaches.
If you pour antifreeze into a frozen air system, it can wash away the lubricants that protect internal valve components, and that will cause them to stick two to three months later.
7. Keep it clean
While your air system needs to be free of water, a regular truck wash can also be the key to protecting air bags, Wiebe added.
The grit and grime that can accumulate around the base of these components can actually wear through the rubber as they flex to accommodate loads.
“It there’s gravel and dirt and hard contaminants in there, make sure that’s washed out.”
8. If it pivots, grease it
Meanwhile, the spring pin’s bushing should be well greased if it’s expected to last from one maintenance interval to another.
“Anything that’s got a pivot should be greased properly,” Wiebe said.
But some of that work can involve tools that are more refined than a grease gun, and he notes that an automatic greasing system helped one of his customers extend the life of spring shackle pins to a million miles or more.
9. Inspect the washers
Rubber blocks are pretty robust, making them a popular choice for rough-riding vocational applications, but related components can still wear out.
A thrust bushing that runs through a block’s aluminum saddle will hold a spike that attaches to a hanger, and this has a washer, Kozier explained. As the cushion begins to wear away, it will force the hanger through the thrust bushing, loosening the washer so much that it moves and jingles at the touch of your hand.
The first time this problem is noticed, the assembly can be re-tightened by adding another washer, he said. But if the washers begin to loosen a second time, you’ll have to replace the rubber blocks.
If the rear end of the truck is wandering all over the road, you may want to ensure that the spike hasn’t sheered off altogether, and the only way to do this is to lift the back end of the vehicle, to see if the wheels remain on the ground while the hanger pulls away from the saddle, he added.
10. Take it easy
While leaf springs are designed to absorb road shocks, they can face added stress when unloaded equipment is allowed to bounce across railway tracks and potholes.
“The quick action has enough energy (to snap them),” Kozier said.
The best way to maintain your components here? Slow down when travelling over rough surfaces.
Without a doubt, these are little steps involving little components, but they can all help prevent major breakdowns.