or decades, a wide variety of add-on devices have been marketed to improve the ride and road manners of the leaf-spring suspension for the Ford F-53 motorhome chassis, which has been the mainstay of the Class A gasoline-powered motorized industry. While many of the add-ons developed by various companies in the aftermarket have tempered the Ford’s road manners to a certain extent, the Ford chassis continues to be known for its stiff ride — and, at times, less-than-stellar handling.
Lafayette, Indiana-based LiquidSpring opted to go in another direction. Rather than attempt to “fix” the Ford’s shortcomings by bolting parts to the otherwise stock suspension, LiquidSpring designed a computer-controlled compressible-liquid “smart” suspension system that is installed in place of the Ford chassis’ steel leaf springs and shock absorbers. The system is available for F-53 chassis with 16,000- through 26,000-pound gross vehicle weight ratings (GVWR), dating back to 2011.
The “liquid” in the LiquidSpring system is silicone-based and compressible under high pressure. Struts (a piston in a cylinder) replace the steel leaf springs. Instead of leaf springs flexing and loading under varying road conditions, the silicone-based liquid is compressed at a variable rate determined by an onboard computer that analyzes suspension movement in milliseconds and changes pressures (2,200 to 4,000 psi) in the struts as road conditions vary. The liquid serves as load support as well as shock absorbing; hence the variability the system provides is a radical transformation of the stock F-53 suspension system.
Beyond the Ford F-53, suspension conversions also are available for Ford-based ambulances and other Ford trucks, plus Ram 5500 and specific International Durastar and Freightliner chassis, buses and work trucks. LiquidSpring products are available through a network of authorized dealers/installers in the U.S. and Canada.
For our test, the LiquidSpring system was fitted on a 2016 30-foot Winnebago Itasca Sunstar (similar to Winnebago’s Vista) with an 18,000-pound GVWR chassis. LiquidSpring initially released only a system for the rear in this application, which did a commendable job of controlling body roll and bounciness. For this installation the front conversion was also made, which dramatically changes the paradigm when it comes to handling improvement and overall comfort while driving the motorhome over rough roadways. We drove almost 5,000 miles (combined, before and after) on a variety of Interstate highways and local roads across six states to road-test this suspension, part of which was a controlled 39-mile course for repeatability.
The Installation
Our test installation, performed in the service department at the LiquidSpring factory in Lafayette, took four days and involved the use of four-corner lifts to provide access underneath the Ford chassis. Removed from the chassis were the four stock leaf spring assemblies and shock absorbers, plus their mounts and hardware — all replaced by LiquidSpring equipment. Among the components built at the Lafayette plant are the struts and pressurized tanks (which the company calls “volumes”), plus the control module/liquid reservoir, mounting brackets and other hardware.
As noted earlier, the actual “spring” in the LiquidSpring system is a strut consisting of a tube and piston. Each wheel strut is connected by a high-pressure hose to a volume, and the pressure in that volume is controlled via another high-pressure hose to the control module.
In our installation, the larger volumes are 6.5 by 38.5 inches, attached by hoses to the rear struts and placed behind the rear axle. On longer chassis the volumes usually are mounted between the axles, which will likely present fewer challenges in locating the appropriate brackets. Volumes for the front struts are 4.75 x 30.75 inches. The size of the volumes may vary in applications for higher-rated chassis.
The process was handled competently and carefully by a company technician who meticulously routed and secured all the components and hoses. Although the front suspension was replaced, the steering components were not altered. Nevertheless, the steering wheel was slightly off-center when the project was completed, a direct result of raising the ride height with the addition of the LiquidSpring suspension components. This is usually an easy fix, requiring the removal and repositioning of the steering wheel; instructions are provided to make any corrections. LiquidSpring technicians normally take care of this during the installation process, but we ran out of time on a Friday, and headed down the road before making the correction.
A Few Words on Tires
The weight increase of the LiquidSpring package (450 pounds) did not justify higher tire pressure than what we were carrying — 80 psi in all tires — and the tires were loaded below their maximum load ratings, which were 7,280 front axle (two tires) and 13,660 rear axle (four tires).
Choice of tires apparently can adversely affect ride quality in the 190-inch-wheelbase 18,000-pound-rated Ford F-53 chassis — possibly more so than in higher-rated chassis with 22.5-inch tires. Stock tire size is 245/70R19.5 and the chassis originally was fitted by Ford with Goodyear G670 tires in load range G, which are known to be comparatively soft-riding tires for motorhome service. The motorhome owner had replaced those with Toyo M154 tires in the same size but in load range H; they had stiffer sidewalls and were over-rated for the weight of the motorhome.
Sales literature for most tire brands in the 19.5-inch size emphasize urban delivery-truck service, not soft ride in a motorhome (except for the Goodyear G670 and Michelin XRV).
The motorhome weighed 17,160 pounds, loaded (water/fuel propane full, supplies aboard) prior to the LiquidSpring installation. Afterward, weight increased to 17,610 due mainly to the weight of the four volumes, the struts and four very substantial control arms front and rear.
Ford’s gross axle weight ratings (GAWR) were 7,000 pounds front and 12,000 rear. Other Ford chassis with longer wheelbases are rated up to 26,000 pounds. Motorhome owners who are considering this installation should acquire accurate weight figures, possibly on one of the many CAT scales at truck stops, because LiquidSpring may decline the installation on a motorhome that already exceeds one or more of its weight ratings.
Road-Testing the Results
“Dramatically quieter. Amazing.” We used those words in describing the level of improved ride and handling of the motorhome after the LiquidSpring installation versus a similar — and extensive — nearly 2,500-mile trip across the same type terrain following the installation.
As an example, ride was dramatically smoother and controlled even on broken pavement riddled with repairs and potholes. The truck lanes on some Interstate highways, such as I-40 east of Albuquerque, New Mexico, were the worst with the stock suspension. The LiquidSpring system substantially reduced the repeated shock impulses transmitted by the stock leaf springs on rough pavement, and it muted the noise.
On curves, the motorhomes did not heel over and yaw, even during aggressive maneuvering. It stayed mostly flat on the pavement; a winding road became a pleasurable drive. Rough approaches to highway bridges were no longer feared. Rapid lane changes produced very little body roll and yawing effect.
“Perceived ride comfort” is the descriptive phrase for the effect of LiquidSpring, according to Bartolone. It is the combination of better ride quality and road manners with less chassis noises, without the annoying cacophony inside the motorhome that translates to less fatigue and more enjoyable travel.
Essentially, the LiquidSpring system transformed the Ford F-53 suspension into something more akin to an air-suspension system on a diesel-pusher coach — and, let’s face it, ride quality is oftentimes one of the reasons buyers opt for more expensive rear-diesel coaches.
Granted, the LiquidSpring smart suspension is definitely not a project for the do-it-yourselfer. However, in addition to its factory installation center, LiquidSpring is associated with a number of independent suspension repair/modification shops in various locations that are available on the company website. Motorhome manufacturers also can order the bare chassis from Ford with the LiquidSpring suspension components already installed; Tiffin Motorhomes and Fleetwood RV, for example, offer the LiquidSpring suspension as an option from the factory.
In most cases, selling or trading a perfectly good gasser results in a big depreciation hit — and when combined with the depreciation of the new motorhome, the financial loss can be substantial. Investing $20,000 in a motorhome in excellent condition that will easily rival the ride quality of a diesel pusher may be the more cost-effective option. Again, there are other factors to consider, including an owner’s level of satisfaction with his or her current gas motorhome and travel patterns, but the numbers will generally favor making the LiquidSpring transformation.
The LiquidSpring system is the first real fix for the historically stiff ride of the Ford F-53 motorhome chassis, and it does an excellent job of improving handling and road manners while reducing interior noise. Combine these benefits with far superior suspension components than the factory counterparts, and the expected improved longevity may be the deciding factor for owners tired of enduring a harsh and fatiguing ride.
LiquidSpring ventured into the suspension business while tasked with finding a solution for poor ride quality plaguing huge off-road trucks used in underground mining. Typically, these trucks rode so rough that operators were being fatigued by uncontrolled vehicle shaking, creating more down time and less production. LiquidSpring prototyped a suspension for the mining and similar industries that suggested compressible liquid could smooth out the ride enough to make a dramatic difference. In short order, production for those companies that adopted the system doubled while the system also increased suspension longevity and reduced repair down time.
The unique suspension proved to be a worthy improvement, but there were no electronics available to manage the process. The challenge was to develop software that would communicate with the system so spring rates could be changed in concert with the capacity of the springs. By 2012, the company developed a model to understand the characteristics of fluid via electronics and introduced the product to the bus and ambulance industries, which offered dramatic improvements in ride quality. As a LiquidSpring company representative explained, in many cases, the bumpy ride to the hospital before installing the LiquidSpring system increased the fatigue and shock already experienced by distressed patients, which actually degraded their health beyond the problems requiring the ambulance ride. Today, 90% of these ambulances are equipped with LiquidSpring components. This type of improvement was not attainable by the auto industry, which struggled to change spring rate for years without success.
Bringing the LiquidSpring system to the F-53 and cutaway chassis, company engineers had to figure out how fluid changes. A fluid model was built to allow engineers to study what happens to fluid under different temperatures, pressure and flow rates for vehicle control. In the end the model provided the company with the electronics to work with hydraulics and mechanical components — eliminating tradeoffs between ride quality and handling. This was a major milestone.
This type of suspension action is achieved with the use of suspension sensors to regulate height, braking, speed and steering input via proprietary algorithms that allow the system to react to body roll in milliseconds — something shock absorbers and air springs simply cannot do.
