In this brief article we are going to discuss the different Chalmers Suspension problems, what the causes are, and Troubleshooting Tips.
What are the most common Chalmers suspension issues?
The most common Chalmers suspension issues are:
- Main Load Rubber Rupture
- Torque Rod bush failure
- Axle Sliding Bracket wear
- Shock Absorber Failure
Chalmers Suspension is an axle-suspension manufacturer that offers suspension solutions to OE’s like Paccar, Kenworth, Peterbilt, Daimler, Freightliner, Western Star, Volvo, Mack, Navistar and Oshkosh. Chalmers Suspension Solutions include Single axle, Tandem axle and three axle truck chassis. The applications of Chalmers suspension are in various construction applications like Dump, Concrete, Garbage, Public Utility, Fire, Mining and many more. The major products that cover these applications are:
- 700 series
- 800 series
- 1000 series
- 1100 series
- 1400 series
- 1800 series
Out of these the 800 series Tandem axle system is the most popular one.
The Chalmers 800 Series suspension can be categorized as a boggie type suspension, but with some very fundamental changes. Conventional Boggies have a Trunion bearing about which the Boggie Spring rotates. But in the case of the Chalmers 800 series, the Boggie Spring is replaced by a ‘Walking Beam’ that rests on the 2 Drive axles via Sliding Brackets, and is supported on the top to contact a chassis upper bracket.
The Axles are constrained in the lateral and longitudinal direction using Torque Rods that are oriented in a diagonally Cross fashion to the chassis. The chassis Crossmember brackets, mounted at the center of the 2 axles, serves as the chassis anchoring points for the Upper diagonal control arms and the Lower Torque Rods.
Unlike in a conventional Boggie suspension, the central pivot point in the Chalmers, is not a rotational axis, but a “Load Rubber” Buffer. The Load Rubber is a large Donut shaped Bush which can flex in all conical degrees of freedom. The Load Rubber therefore provides stiffness in all the degrees of freedom, i.e. Axle Roll, Cross-Articulation, One axle Full Bump and Tandem axle Full Bump.
How does the Chalmers tandem suspension work?
Load from the axles is transferred to the walking beam. The Walking beam compresses the load rubber by squeezing it between the walking beam and the Conical Striker plate (Which is in contact with the chassis bottom rail. In Rebound, the Walking beam rests upon the chassis crossmember support bracket
In Cross-articulation, when one of the axles travels upwards into bump, the walking beam strikes the load rubber and transfers the load to the other axle by pushing it downwards.
Main Load Rubber Rupture/Breakage
- The central pivot Load rubber tends to weather and crack after continuous cycles of loading and unloading
- After long periods of service, the Load rubber loses its elasticity and tends to rupture faster
- Load Rubber Rupture leads to a Noisy suspension and a poor and harsh ride quality
- As a countermeasure to further improve service life, the Original Load Rubber can be replaced with a compatible aftermarket Polyurethane, or any other durable material.
- Poly bushes also have the advantage of being resistant to corrosion by chemicals and a much longer service life as compared to Rubber.
Torque Rod Bush Failure
- There are a total of 8 Torque Rods (4 above and 4 Below) that connect the chassis to the 2 drive axles via rubber bushings
- The torque rod bushes wear out and tear over time.
- Since there is no Anti-roll bar for each axle, the torque rod bushings resist the axle roll motion.
- Torque Rod Bush wear out, therefore leads to problems in Handling behavior of the truck and noisy suspension on rough surfaces
- The bushes, which are typically of rubber, are of a serviceable design and can be replaced with aftermarket poly bushings which offer orders of magnitude improvement in service life.
Axle Sliding Bracket Wear
- The Center Beam (4) contacts the Axle sliding bracket (7) with the wear pad (5) as interface
- The wear pad ( as the name suggests) is the sacrificial part that wears out in order to prevent contact between the Beam and the Axle sliding bracket.
- It is suggested to regularly inspect the condition of axle sliding brackets. If they wear out excessively, there is a risk that the Beam may contact the axle sliding bracket directly, resulting in major repair bills.
Shock Absorber Wear
- If the shock absorber fails, it results in a bumpy rear ride and harshness going over rough surfaces
- Generally, the shock absorbers would show signs of oil leakage, when they have failed.
- Generally, the shock absorber top seal is the first to fail
In this brief article we have discussed the different Chalmers Suspension problems, what the causes are, and Troubleshooting Tips.
Frequently asked questions
What is the difference between a tandem Boggie Suspension and the Chalmers Suspension?
- The conventional tandem boggie suspension uses a walking beam inverted leaf spring to transfer loads between the 2 rear axles. The boggie springs are hinged on a Trunnion, which is mounted on the axle.
- The Chalmers suspension uses a walking beam and conical rubbers to transfer loads between the 2 rear axles. The walking beam is a floating type supported on the axles only using sliding saddle bracket supports
- The tandem boggie suspension is much heavier in weight and therefore suited to heavy duty applications like mining wear suspension loads are higher and environment is harsher, like in deep mining. Rubber would have durability issues, whereas steel spring could last longer in mining conditions.
- The Chalmers Walking beam rubber suspension is suited to lighter tonnages and construction applications
How do you align the Chalmers suspension?
- The Chalmers axle suspension is aligned by adjusting the length of only the Lower longitudinal Torque Rods. The upper Torque rods cannot be used for alignment. The rear axle/s is aligned for Castor alone since it is a rigid axle.
- Before starting the alignment procedure, it is important that the Torque Rod Bushes need to be relieved of any cornering compression by fully lifting the chassis frame and allowing the axle to hang. On bringing the axle back on the ground, visually check whether the bushing rubber appears squeezed to any one side.
- Perform the alignment readings for one of the axles first and then the other.
- The Torque rods are of 3-piece construction. The Torque rod is connected by threaded joints to the Rod eye ends. The threaded joints are held secure by way of Pinch bolts.
- Loosen the Torque rod pinch bolts and loosen the torque rod threads by rotating the rod using a pipe-wrench. Use penetrating oil if needed.
- Rotate the torque rods in order to increase or decrease the torque rod length according to the alignment readings.
- Once the right alignment is achieved, tighten the pinch bolts of the torque rod ends to 65 ft.lb of torque.
Is Chalmers Suspension air ride?
The Chalmers 1800 series has a 4-air bag single axle air suspension system. The basic setup is a trailing arm Torsion beam axle with two air bags ahead and 2 air bags behind the axle. The biggest advantage of the 1800 series is that it ensures the best possible ride quality with a really lightweight system. The capacity of the Chalmers 1800 series axle ranges from 23000 to 26000 pounds.
Is walking beam suspension good?
A Walking beam suspension’s primary intention is to provide the maximum articulation while keeping the rear axles in tandem. The walking beam allows the axles a high degree of roll and at the same time transfers loads between the rear axle-1 and rear axle 2.
The Walking beams best application is in construction and mining industries, where Off-roading is the norm. In mining or construction, the payloads are always at rated or slightly more, since quick material movement is the most important objective. A Walking beam suspension is rugged and has the capability to haul heavy loads over extremely uneven surfaces.