TORONTO, Ont. - There's a lot riding on your suspension system. Literally. In addition to supporting the weight of cargo and equipment, related components need to deal with the stresses associated wit...
MAINTAIN IT: If you want your suspension to last, it’s important to keep it properly maintained. Today’s suspensions generally require modern shocks to shoulder more of the stress, according to John G. Smith.
TORONTO, Ont. – There’s a lot riding on your suspension system. Literally. In addition to supporting the weight of cargo and equipment, related components need to deal with the stresses associated with every turn or bump in the road.
Consider following these 10 tips to preserve a smooth ride:
1. Grease it good
This advice may appear overly simplistic, but the proper application of grease is still a key step in any preventative maintenance regimen.
Just keep in mind there are a few tricks of the trade to ensure that the grease flows where it should. For example, to ensure grease fills the cavity at the bottom of center and spring eye bushings – where it is needed most – use a hoist to relieve the suspension of its load. Then apply the grease gun with confidence.
2. Torque it tight
Considering the stresses that they’re under, fasteners associated with such things as axle connections, spring eyes, saddle caps, torque rods, bushing retainers, shocks, air springs and leveling valves should all be checked and re-torqued at least once a year.
3. Get in line
Irregular tread wear can offer an early indication of vehicle alignment problems. The good news is that a re-alignment is usually an affordable repair, and often includes little in the way of parts other than a few well-placed shims.
4. Learn the shock truth
The friction and limited travel associated with old multi-leaf suspensions tended to absorb a lot of energy, but today’s air and tapered leaf spring suspensions require modern shocks to shoulder more of the stress.
Shocks are responsible for keeping tires from hopping along the surface of the road, and prevent damage associated with chassis vibrations. But early signs of trouble can come in the form of an uncomfortable ride, uneven tire wear, or the premature failure of cooling and electrical components.
Related maintenance tends to involve the regular replacement of bushings, but you’ll also want to watch for visible signs of damage including dents, enlarged mounting holes or oil leaks.
Still, don’t be (ahem) shocked by every sign of fluid on the outside of the shock. Some oil is bound to evaporate and escape through the upper seal. The grime on the outside may simply have been formed by fluid that has condensed after being exposed to cool air. (Combined with simple road grime, it can look pretty ugly.)
The true signs of trouble come in the form of streams of fluid that can be traced to the upper seal. You’ll simply need to extend the shock as far as possible to see it.
Meanwhile, a sense of touch is one of the most effective tools to determine if a shock is working the way it should. Drive at a moderate speed for about 15 minutes and park the vehicle. Touch a nearby part of the chassis to establish an idea of the ambient temperature, and then touch the shock just below the dust cover or tube.
A working shock will always be warm to the touch.
5. Choose better bushings
Rubber center bushings are fine for many applications, but premature bushing failures may give you a reason to switch to aftermarket alternatives such as urethane designs, which won’t deteriorate as fast as their rubber counterparts, or intermediary designs made of rubber and bronze. Severe-duty applications may require such things as fully bonded rubber bushings, while equipment exposed to an unusual number of tight turns may require bronze bushings. The latter designs may require regular grease applications, but they can last much longer as a result.
Signs of worn bushings include trailers that wander back and forth, unusual rattling sounds, and ragged or loose pieces that protrude from connection areas. And if there’s too much lateral movement in a beam center bushing, the inside walls of the tires may actually begin to rub against the suspension frame hangers.
Excessive free play can usually be identified by applying a pry bar to the questionable part.
6. Take care of torque rods
Torque rods control driveline angles, absorb forces that relate to corners, and restrain the axle housing whenever you accelerate or brake.
Luckily, an upper torque rod can last the entire life of a walking beam suspension as long as the related bushings are replaced on a regular basis. Inspections should also include checking the related locknuts that fasten the attaching ends of the straddle mount rod and tapered rod.
7. Ensure welds are well
A trailer that leans from one side to the other may tell a story of missing or broken axle welds. In contrast, if it always leans in one direction, the suspension’s beams may not have been installed parallel to each other.
A visual inspection of the various welds in a suspension system should look for signs of cracks at mounting plates, frame brackets, pivots, gussets and hanger attachments.
8. Listen to the air
Air springs should never be allowed to rub against tires or loose steel, and should be regularly checked for any signs of cuts or abrasions.
If an air spring is entirely flat, however, listen for any air that may be leaking from points including fittings, the control valve or brake actuators. And if the air spring suddenly deflates whenever you park the vehicle, coat the paint-can-sized part and its connections with a solution of dish soap and water. Air leaks will appear in the form of bubbles.
If the air springs will not inflate when you add weight to cab, or will not deflate when weight is removed, the height control valve may need to be replaced.
9. Deny delaminating
Inspections of rubber bolsters should involve lifting a suspension on a hoist, to check for any signs of delaminating, where the rubber blocks separate from steel plates. Some tolerance will be allowed, but use a machinist’s scale to ensure the gaps have not expanded beyond an acceptable distance.
10. Know your slide rules
Slider assemblies should be checked for missing hardware such as errant bolts, retainers, pins and hold-down clips, and all fasteners should be torqued to recommended levels. The sliding mechanism itself – such as the pull bar mechanism and locking pins – should not show any signs of excessive wear or binding.n