Review of the Timbren SES Severe Service Spring for Truck Campers

Without a doubt, rear sag and sway are the most common suspension issues for trucks hauling truck campers. Rear sag occurs when a truck is either over matched or when a truck is hauling a load near its max load rating or payload. Not only does rear sag look bad, but it can make a truck wallow in turns, and feel light when steering. Fortunately, most pickups are engineered with a nose-down rake to offset heavy loads, but rear sag can still happen. The other big issue, sway, occurs most commonly on curves or when making sharp turns. A truck suffers from sway if it feels like it’s going to roll or tip over when steering. The sensation can be quite unnerving, especially on winding mountain roads with steep grades. Fortunately, there are a handful of aftermarket upgrades that can be purchased to resolve these troublesome suspension issues. One of the better modifications you can make to your truck are those made by Timbren Industries. This is a review of the Timbren Suspension Enhancement System (SES) Severe Service Spring for truck campers.

If you’re not familiar with Timbren’s SES, its pretty neat. It consists of two rubber spring assemblies that are mounted in place of the jounce bumpers that came with your truck. These Canadian-made springs sit about an inch above the rear axle unloaded. When your truck camper is loaded, the SES springs engage your axle. As you drive, the rubber springs expand and contract, providing your rig with proper load support. Timbren also makes an SES Severe Service kit for hauling extra heavy loads like truck campers. This is what we installed on our truck, a 2013 Ram 3500 4×4 SRW. Unlike the regular SES kit, the Severe Service kit is designed to rest on your axle in an unloaded state in order to provide maximum load support for your truck. The Timbren’s Severe Service kit can support up to a whopping 8,000 pounds, a full 3,000 pounds more than the typical air spring system.

The heart of the Timbren SES is the patented Aeon rubber spring. You’ll find a pair of these hollow rubber springs in every SES kit you buy. The company has a saying that their Aeon springs are “stronger than steel, more reliable than air,” and there’s a ring of truth to these words. Timbren’s Aeon springs will neither rust nor will they leak. Indeed, many of Timbren’s Aeon springs are still going strong after 30 years of service. In fact, all SES kits come with a lifetime warranty for as long as you own your truck. The number of Aeon springs found in each kit varies. When space between the axle and frame is limited or when extra support is needed, a single convoluted rubber spring is used. Conversely, when space between the axle and frame is plentiful or when a better ride is desired, the taller double convoluted Aeon spring is used instead. If you’re hauling a truck camper you’ll want to get the Severe Service kit with the single convoluted springs. Compared to the double convoluted springs, the single springs allow for less travel and delivers more load support for truck campers.

timbren ses - Truck Camper Adventure


Any Review of the Timbren Suspension Enhancement System has to address the installation. Overall, installation of the Timbren SES kit was extremely fast and easy. In fact, we’d have to say it was one of the easiest modifications we’ve ever made to our truck. To perform the swap out, all you need to do is crawl under the truck, remove the two OEM hex screws that hold the jounce stops in place, and install the SES springs using the same OEM screws. Contrary to the installation instructions, we had plenty of room between the axle and frame to install our SES springs, so lifting the truck wasn’t necessary. You’ll need a socket wrench with an 6-inch extension to mount the springs to the brackets and you’ll want to place the brackets in a vise during assembly so that sufficient torque can be created to fully seat the screws into the brackets. In order to improve axle articulation and maintain the stock ride, we modified our SES springs by removing the 1-inch rubber spacer so that the springs come in contact with the axle only when the truck camper is loaded. This extra 1-inch allows for more axle movement and articulation off-road and that’s a good thing. In all, the entire installation took 45 minutes, tops.

Timbren SES - Truck Camper Adventure
The OEM Jounce Bumper (left) and Timbren SES Severe Service spring.
Timbren SES Severe Service - Ram 3500 - Truck Camper Adventure
Driver side unloaded Timbren SES Severe Service spring.
Timbren SES Severe Service - Ram 3500 - Truck Camper Adventure
Engaged (loaded) driver side Timbren SES Severe Service spring.

The Verdict

How well does the Timbren SES work? How well does it eliminate rear sag and sway? Exceptionally well. In order to put the Timbrens through an effective test, we removed the rear sway bar and we have to say that the Timbrens perform just as well if not better in eliminating sway than a sway bar. The big negative with a rear sway bar is that one end has to be disconnected to allow the rear axle to freely articulate when driving off-road. No such adjustments are necessary with the Timbren SES. Just install it and forget about it. What about rear sag? Honestly, we didn’t have much to begin with, but what little we had before is all but gone now. One of the biggest benefits that we’ve been able to derive from the Timbren SES is a smoother, better ride off-road. We no longer bottom out when hitting surprise bumps and holes and that alone is worth the investment in that it protects my rig from damaging shocks and vibrations.

Is the Timbren SES better than the traditional air bag system in addressing rear sag and sway? We wouldn’t say that one works better than the other. However, we will say this. Having owned both, we prefer the simplicity and durability of the Timbren SES. Sure, air bags are adjustable, but they’re also more complex, prone to leaking, and aren’t particularly suitable for extreme off-roading. The Timbren SES, on the other hand, excels on all types of road surfaces and doesn’t require any maintenance, adjustments, or pressure checks. Are there any negatives associated with the Timbren SES? Just a couple. Bumps and imperfections in the road are felt a bit more when the springs are engaged, but that’s the price you pay for resolving handling issues that put your rig at risk. To us, it’s a very fair trade off. What would we rate the Timbren SES? On a scale of 1 to 5, we enthusiastically give the Timbren SES a rating of 5 stars. It’s a winner!

About Mello Mike 908 Articles
Mello Mike is an Arizona native, author, and the founder of Truck Camper Adventure. He's been RV'ing since 2002, is a certified RVIA Level 1 RV Technician, and has restored several Airstream travel trailers. A communications expert and licensed ham radio operator (KK7TCA), he retired from the U.S. Navy in 2004 as a CWO3 after 24 years, holds a BS degree, and now runs Truck Camper Adventure full-time. He also does some RV consulting, repairs, and inspections on the side. He currently rolls in a 4WD Ram 3500 outfitted with a SherpTek truck bed with a Bundutec Roadrunner mounted on top.


  1. Bill Hamilton here. I live a few miles from where Timbren suspension parts are made.
    When I installed my upgrade on my 2003 Dodge 2500 long bed pick-me-up truck I found the slots in the mounting brackets were way too wide for the hardware and the bolt heads even with washers did not cover enough of the slot sides to provide a secure installation. I brought this to their attention and suggested a fix of a spacer that fits in the slot. I made my own on my machine shop and they work great. They are essentially a very large washer with a lug that is proud and fits the slot and prevents movement of any kind. I also drilled the bolt hole for a close fit as well. I can see they have not made any changes to their brackets.
    If you are going to install these, and they are a great product, take the steps to ensure they are not going to move once installed. Currently I have little confidence in their security of staying in place.

  2. For a 2” lifted 148” F350 with a full CJC/King set up would you take the regular one to maintain axel movement off road, or the severe duty version?

  3. I just installed a timbren system in my 2014 f350 4wheel drive ford. our first trip pulling a 36 foot 5th wheel was surprising the ride didn’t feel to bad but when we opened the trailer the ride had obviously been a lot rougher for the trailer. furniture was all over the place the fridge door had jarred open and our printer had been smashed.
    Same roads we have traveled before with no damage. can I do something to soften the ride or will that defeat the purpose. I’m concerned for the structual integrity of the trailer

  4. Carol I have 2003 4Runner that we use to pull a similar weight trailer with when we first started camping. At that time I put in Air Lift 1000 bags. The bags have since dried out not sure if that because of our frigid Canadian Prairie winters or just age. The bags no longer have the plyability they use to even though they hold air. They performed well for the first few years. When we up sized to a 5000lb trailer we bought a Avalanche and after doing research I choose to go the Timbren route over the air bags and they worked out great. We have since up sized again to a 7500lb trailer and use our sons F250 and I was so happy with the Timbren’s I put them on his truck after just one trip with it. It stopped a majority of the rear end sag, made setting up the weight distribution hitch easier and took the bounce out of it while traveling down the road. At work I drive a Ram 1500 with 1000lbs of payload everyday. The company choose to install the Air Lift 1000 with onboard compressor and wireless remote for nearly $1500 Cdn on 3 trucks, I wasn’t asked for my opinion. In less than a year all 3 trucks has blown bags out, the first sets were replaced on warranty. When they go this time it is my recommendation that we buy the Timbrens. Installation is quick and you never have to worry about them again. Hope this helps.

  5. I have a 2011 Toyota 4Runner 4WD with factory tow package. In the spring I will be taking delivery of a 3000 pound/dry weight dual axle travel trailer. Since Runners have a tendency for saggy rear ends, I have been considering air bags. then somebody suggested the Timbren System. Now I am confused and not sure which would be best for me. ??? Thank you !!!

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