By Randall Brink
If you have a newer Class C motorhome or a Class A manufactured since the mid-1980s, there is a good chance that your coach has an air ride system with “air springs” as part of its suspension. The system may seem shrouded in mystery because its components are underneath the coach chassis. If everything is in good working order – out of sight and out of mind. But like all coach systems, the components are subject to wear and tear from use and should be inspected regularly.
The two primary components of your suspension system are airbags and shock absorbers. Most everyone is familiar with the latter because most cars and trucks have them, and they are an item that needs replacement every few years or after, say, 100,000 miles.
Air bags are rubber. The same type of rubber as tires. Rubber deteriorates with age.
What does the air spring system do?
The airbag system under your coach has three functions. First, the system lifts the coach to “ride height” or a level well above the tops of the tires when the coach is in the travel mode. Second, the air suspension levels the coach, both while underway and while parked in camp. And finally, the system provides a cushioning effect that substantially enhances the smoothness of the ride while on the road.
How does the system work?
The airbags are mounted forward near the steer wheels and the aft dual wheels. There are pneumatic lines that connect the bags to an engine-driven air compressor that inflates them and allows the operator to maintain a level coach body by adjusting valves with controls located, generally, near the driver’s seat. The valves let air out of front or aft airbags and/or left or right airbags to achieve level.
What do you look for when inspecting the air ride system?
Condition of airbags and pneumatic lines.
How can you tell when it is time to refurbish your air springs?
Airbags are tough and built to handle the inflating, deflating, and intense air pressure. But they are made of rubber, and rubber deteriorates with age, as with tires. Airbags should be inspected for integrity as a matter of pre-departure routine. The system should get special attention if there is any indication of low airbag inflation, airbag failure, the sound of an air leak, or failure of the coach to reach level ride height. In addition, if your coach is more than ten years old, it is time to start carefully inspecting for cracks in the rubber, heavy oxidization, or the appearance of bare cords (see below). An exposed cord should prompt an immediate plan for an airbag replacement, just like visible cords on a tire.
Replacement airbags and associated components are typically sourced from your coach manufacturer or many parts outlets, particularly those that supply Class A RVs or commercial trucks. There are also discount parts suppliers online, such as SDTruckSprings.com and FinditParts.com. It is worthwhile to shop carefully, referencing the specific part number(s), as there can be a wide range of pricing for a given airbag part number. I have personally seen a difference of as much as $80-$100 per airbag! A Class C coach with air spring-assisted suspension has two airbags.
Do it yourself?
The handy motorcoach owner will likely consider doing an airbag replacement project themselves. However, remember that this project involves raising the coach, blocking it safely, and dismantling the air ride suspension system. Older coaches sometimes have rusted or corroded airbag attachment brackets which are very difficult to get off. Air supply valves and fittings might also be worn and require new parts, and sometimes those components are located in very tight quarters near the wheel wells and bulkheads. And again, I stress, if you are going to do any work underneath the coach, ALWAYS USE FRAME BLOCKS!
Leave it to the pros
In my case, in the end, I decided to leave it to the pros.
I found cracking and some bare cords on the airbags and called my favorite heavy-truck shop, Ross Point Truck Repair, in Post Falls, Idaho. Their truck chassis technicians change dozens of these systems out every year. They have the parts, tools, and know-how to get the job done right.
If your coach won’t level or ride right, or rides like a hay wagon instead of a Bentley, take a close look at your air ride system.
This article originally appeared on RVtravel.com in October 2021. It has been updated for accuracy.
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CV boots and air bags last longer if sprayed with a silicone liquid like Black Magic, every oil change.
I have never seen anything in print on an age limit of “Airbags” but since they are rubber, like our tires I see no reason to expect them to last much longer than the 10 year max life of our tires.
Great article.
I installed SumoSprings on our single axle TT this past spring. They have done an amazing job of minimizing trailer bounce. The core is high density urethane foam – somewhere between rubber and plastic. Any idea how long this material might last?
After reading this great article I went looking for “ALWAYS USE FRAME BLOCKS!” & didn’t find any. Does anyone know where to get them or even what they are? Aside from using large pieces of lumber!
Snoopy
Dave, very heavy duty jack stands with locking pins, and a proper hard and level surface to set them on, are fine. I run down my hydraulic jacks, put in the HD jack stands, then adjust the hydraulic jacks so the coach frame rail is on the jack stands but the hydraulic jacks are still touching ground. I then have both systems protecting me in case one or the other fails.
DO NOT RELY ON JUST RATCHETING TEETH OR HYDRAULICS IN A JACK STAND. YOU ALWAYS WANT A PHYSICAL PIN TO LOCK IT IN PLACE.
You can also use wood blocking, but that is not the handiest. Jack stands are designed for the job. HD stands aren’t cheap.
Hi Mike yup I know all of what you said, however it didn’t answer my question regarding what are “FRAME JACKS” Actually I bought a pair of 12T jacks that are 22.2 inches tall & they were still about 4″ short of supporting my 2017 Berkshire Forest River 34QS Class “A” motor home Freightliner frame in the rear, sent them back!
Thanks
Snoopy
The opening statement is WAY too broad!
Gasoline chassis A’s and C’s would not have an air ride system and gas units make up the majority of motorized units, especially in the C class. Diesel chassis “Super C” and Class A motorhomes are where you will generally find air suspension systems.
In addition, most diesels don’t have driver controls to adjust air bag leveling. The cockpit controls are dump the air completely or the system self manages, which is not reliable for campground leveling, hence leveling jacks are used. High end units may have complete driver control from the cockpit and avoid jacks, but that is not the case for low or mid level diesels.
Another important thing with air systems is to perform the needed maintenance on the air dryer system. This critical component removes the moisture from the compression of the air and ejects it. Older units may require owners to occasionally release air from the air storage tanks via lanyards attached to valves to purge moisture from the tanks.
Air systems are great, but they require another level of owner knowledge, maintenance, and cost.
See the above information from me.
Thank you for this article! Right on! I have a Class A 34′ 1994 GM gas 454 with full rear air suspension as provided to Winnebago by JetCo (Iowa). The original Firestone bags are still on it, albeit cracks from aging are showing up. I bought two for replacement and carry them in the event of failure on the road and finding them in Podunk, MN! i did experience a failure some years go which makes the vehicle basically not driveable as there is only 1/2 of leaf spring on each side; so it is frame to axle direct contact. The failure was caused by the small 3/4″ rubber tube from the accumulator to the air spring. They are bent at 90 deg with a stainless steel spring inside.
I had just had new tires installed and the failure happened on the way home. It broke the slide hangers on the rear bedroom drawers among other things jarred loose; at only 15 mph max!
Also this system is self leveling, however it is controlled from the instrument panel either manually or automatically. I do not have leveling jacks and have only needed to put a block under the wheels once in several years! I use the manual adjustment mostly to level the refrig. while setting up. The Firestone air bags are robust being manufactured for semi trucks and trailers.