Why do medium/heavy-duties offer substantially more rear suspensions for any given make and model truck?
With countless suspension options available in the medium to heavy duty market, what should owners consider when selecting the most suitable rear suspension for the job? We recommended keeping the following 10 points in mind:
1. Payload Requirements
Payload requirements are the most significant thought for right suspension choice. What the truck will pull, the amount it gauges, and the potential for over-burden. A right suspension spec should leave a little cushion for payload limit, without going past its boundaries. An overloaded suspension can cause a harsher ride, less safe travel and more costly repairs.
2. Suspension Type
For medium-duty trucks, from 14,001-lbs. to 26,000-lbs. gross vehicle weight rating (GVWR), there are two predominant suspension types:
- Multi-leaf. Multi-leaf suspensions provide extra stability and rigidity in applications that require heavy loads on the rear axle, They’re also cost effective and provide a good fit for purchases driven by price.
- Air ride. Air ride suspensions provide for superior ride quality, and there are several that have been specifically designed for vocational applications. The suspension’s air-dump capability lowers the chassis height and enables easier loading and unloading, Air ride suspensions also carry a higher price tag than multi-leaf spring suspensions.
3. Ride Quality
A suspension that is too rigid for the application will ride rough and cause discomfort for the vehicle operator. For applications where the truck is typically always laden, such as service and lube trucks, this [rough ride issue with rigid suspensions] is minimized.
4. Roll Stability
High center-of-gravity applications need suspensions that have horizontal roll stiffness to keep the vehicle upright and tracking properly.
Trucks that routinely carry heavier loads need a suspension that has vertical stiffness to support the weight and also minimize performance issues and maintenance concerns.
In construction and other off-road applications, where the terrain can be rough and uneven, suspensions with high degrees of articulation may be required to maintain a maximum uniform down force at all wheel ends to prevent the suspension from bottoming out. This will likely mean going to a heavier weight suspension to achieve the needed level of articulation. The high articulation provides better traction and maneuverability on rougher terrain.
7. Suspension Weight
The weight of the multi-leaf and air ride suspension in the 10,000-lb. to 18,000-lb. capacity range are quite comparable, with the air ride suspension typically weighing about 20 lbs. lighter. Air springs can be built lighter than steel leaf springs. This plays more of a factor in heavier applications where the increased suspension weight affects payload capacity.
8. Cargo Type
An air suspension, for example, offers a smooth ride that provides a better means of protecting fragile loads.
9. Chassis Wheelbase
In short wheelbase configurations, it can be more difficult to locate air suspension components and find room for air reservoirs and other chassis requirements.
Sandi Auto and Truck can help you to determine whether there are any potential compatibility issues with chassis wheelbase and rear suspension requirements.
10. Overall Cost
What attributes – such as ride quality, roll stability, durability, and weight – are most needed? What are the trade-offs? Specifying too much suspension adds to the cost. Also, air ride suspensions, while offering superior ride quality, come at an increased cost over multi-leaf suspensions.