Weighing in on trailer spring suspension TCO

Weighing in on trailer spring suspension TCO

Sponsored by Hutchens Industries

Increased payload and trailer uptime are prime factors in determining the total cost of ownership (TCO) calculation when considering a suspension system. Tried and true spring suspensions have been serving trailers well years and for good reason: The initial lower acquisition and maintenance costs of yesteryear are now married to continued improvement in mechanical spring technology. Springs have always had a progressive rate to ride as soft as they can when the load is lighter and then provide higher roll stiffness as the load increases.

To determine what type of suspension fits your fleet, you have to consider the weight of the entire trailer, the load and the uptime requirements. The uptime expectations are easy to define for all fleets—you never want any downtime, and uptime often relies on your fleet’s dedication to regular preventative maintenance. So let’s take a look at how payload and application will impact your suspension selection.

With all suspensions, there is a push and pull between cargo safety and driver comfort. Safety and control of the trailer typically comes at the cost of the ability to dampen and absorb inputs from the road. That’s because the stiffness of the spring affects how the sprung mass—the mass of the trailer supported on the springs—responds. The stiffness is affected by the ratio between the sprung and unsprung mass—the weight of the axle, brake and wheel end systems. For example, when a tire absorbs impact and bounces vertically, a loosely sprung suspension (or one where the sprung and unsprung mass are isolated) will better accept vertical movement and help dissipate the vibrations to protect the cargo. Conversely, a higher sprung mass will push down on the wheels and keep the tires on the ground to maintain trailer control.

To meet the demands of both driver comfort and cargo safety, mechanical suspension technology has evolved through the use of lighter, higher-strength steel to reduce weight. Additionally, natural rubber bushings are used to maintain durability, fastening technology improvements minimize maintenance and expansion of spring types provide improved cargo protection for a wide range of applications.

Springs absorb energy to protect the load. They can only absorb so many road inputs until they eventually reach the end of their fatigue life and you have to replace the springs. Yet the durability of today’s mechanical spring suspensions in applications where road conditions and payloads remain relatively constant means that, often times, the suspension will outlast the life of the trailer as long as you maintain your suspensions.

In terms of mechanical spring suspension maintenance, most preventative maintenance focuses on keep the fasteners properly tightened. Preventative maintenance consists of a periodic torque check of all fasteners along with routine pre-trip visual inspections to make sure that none of the moving parts have reached the end of their life.

In the event that a spring does need replaced, should be replaced at the first opportunity, but some types of spring failures require placing the vehicle out of service immediately. (The Commercial Vehicle Safety Alliance (CVSA) defines out of service criteria for suspension springs and their handbook can be consulted for further definition.) Replacing a spring in a mechanical suspension can be performed on either a loaded or unloaded vehicle as long as the shop is properly equipped with the necessary lifting and safety equipment. The process involves lifting the load off of the spring to be replaced, removing the U-bolts attaching the spring to the axle along with any spring retainer bolts in the rockers and/or hangers, and then removing the spring from beneath the trailer.

After inspecting the suspension hangers and/or rockers for excessive wear, a new spring of the same type can then be re-installed. It’s important to always use new fasteners when replacing a spring and make sure that they are properly tightened. Shop times vary by location, but changing a spring should take less than an hour.

For more information on mechanical spring suspensions, visit the Hutchens Industries website.

You May Also Like

Scania opens orders for autonomous mining trucks

Scania’s 40-tonne autonomous heavy tipper for mining available to order, and the 50-tonne model to follow shortly afterwards.

Scania-autonomous-mining-truck

Scania announced that it has begun selling autonomous mining trucks, with s 40-tonne autonomous heavy tipper for mining available to order, and the 50-tonne model to follow shortly afterwards.

Sales of Scania autonomous mining solutions will start in Australia, with first deliveries and start of operation scheduled from 2026. Scania believes the next market will likely be Latin America, a region where it has significant market presence in the mining segment. 

FTR: Truck orders exceed recent trends in May; vocational sales stand out

Not only are orders up m/m and y/y, FTR said this level is above recent demand trends and 2% above the average for May over the past decade.

FTR-May-Preliminary-Class-8-orders
PACCAR MX-13 CARB compliant engine available in Peterbilt 579, 567, 589

The PACCAR MX-13 diesel engine meets the CARB Omnibus Regulation and is available in high performance or efficiency focused ratings.

Cummins, PACCAR, Daimler Truck N.A. complete joint venture formation

The completed joint venture is now known as Amplify Cell Technologies.

Accelera-Daimler-Paccar
FTR sees rise in April trailer orders

With 13,016 units sold, April saw 9% m/m and 45% y/y gains. However, trailer orders were still 20% below the average for the last 12 months.

FTR-april-trailer-orders-chart

Other Posts

FTR: Neutral outlook despite Shippers Conditions Index improvements

Stable diesel prices and slightly more favorable rates resulted in a better market for shippers in March, but conditions may deteriorate soon.

FTR-Shippers-Condition-Index-March-chart
Food Forward Inc. uses Volvo VNR electric to fight food insecurity

Food Forward says food insecurity and climate change are interconnected global issues, and this move helps address both at once.

Food-Forward-Volvo-VNR-Electric
Daimler Truck N.A. to add EV training center, engineering facility to Oregon HQ

The investments include a new Electric Vehicle Supply Equipment (EVSE) training center, and a new engineering facility.

Daimler-Portland-HQ-Clean-Transport-investments
AiLO places 100-truck order of Nikola hydrogen FCEVs

Scheduled to start delivery in 2025, Nikola says this new order is for double the amount of trucks AiLO ordered in 2024.

Nikola-AiLO-Logistics