Additional Images

Spring Under Axle Configuration Trailer Kit | Timbren SES Suspension Enhancement System

This SES suspension upgrade fits your trailer suspension with an underslung axle setup that has a 2-3/8” up to 3” diameter axle with 2” wide leaf springs. Each laser cut piece of steel is precision bent and powder-coated to ensure a quality fit. Our hollow rubber springs are designed to deliver a progressive spring rate. In other words, the more weight that pushes down on the rubber springs the harder they work to prevent sag and stabilize the load.

This kit is rated at 5,000 lbs capacity. Even though you’re increasing the spring rate by adding this upgrade, this does not increase the trailer’s GTW. Please make sure that the load does not exceed the GTW (Gross Trailer Weight) set by the manufacturer.

Pricing: $479.14
Free ground shipping (some exclusions may apply)


Timbren SES upgrades are designed to keep your trailer level at all times. This will improve safety and stability.

If extra weight makes your trailer top-heavy, you’re going to experience roll and sway. There’s nothing more challenging than trying to keep your trailer moving in a straight path when the load is unstable.

Timbren SES suspension upgrades offer you more stability and peace of mind by eliminating suspension sag and reducing roll & sway on your trailer.

What Is An Underslung Trailer Suspension?

An underslung axle refers to the way the leaf spring sits below the axle instead of above the axle.



  • Eliminate Trailer Squatting & Sagging
  • Cushion Road Shocks
  • Improve Handling
  • Tow & Haul Trailer With Safety & Confidence
  • 100 Day Money Back Guarantee
  • NO B.S. Lifetime Warranty


  • Rated for 5000lbs
  • Overall kit height = 5.25”
  • Compatible with 2-3/8” up to 3” diameter axle with 2” wide leaf springs

What's Included In The Box:

  • 2x Aeon® hollow rubber springs
  • 2x Steel mounting brackets
  • All necessary hardware


Timbren SES products come with a Lifetime Warranty which includes:

  • Defects in material and workmanship
  • Damaged parts under normal use and service

Warranty limitations include the following:

  • Warranty applies to original purchaser
  • Warranty is not transferable to another vehicle
  • Warranty does not include labor, freight or collateral damage
  • Timbren reserves the right to inspect the failed part and ask for proof of purchase.
  • Timbren will not warrant the product in the event of alteration, misuse, overload, negligence or damage cause by others.



I installed a rear kit on my pickup truck and its almost touching the axle. The installation instructions indicate that I need a 1" gap. What should I do?

Remove the rubber spacer supplied in the assembly. If you have already done this or if there is no spacer in the kit then take the vehicle out for a test drive. Often with a vehicle having a partial load, or a vehicle having an older suspension, the rubber spring may be in contact with the axle with no adverse ride quality. If ride quality is poor, contact Customer Service.

I installed a rear kit on my pickup truck and there is more than 3 inches of gap between the rubber spring and the axle. Is this ok?

Ideally, you want to adjust the rubber spring assembly to a gap of about 1 inch. In most cases this can be done with a spacer included in the kit. If you have already installed everything included with the kit, and you still have too much gap, contact Customer Service.

The capacity rating of the Timbren SES kit seems awfully high. I am sure that I do not need that much capacity for my application. What do you recommend?

The real question you seem to be asking is Will this give me a rough ride? The products progressive spring rate provides superb ride quality with any load. Also when cornering, swerving or in high wind situations, the improved stability offers great performance and peace of mind.

I'm experiencing a rough ride when my vehicle is unloaded. Can this be fixed?

If you have installed the Timbren SES (Suspension Enhancement System) and find that the vehicle ride quality is poor when empty, measure the gap between the rubber spring and the axle. (See Question and Answer #1 for further details and solutions.)

The rubber spring is touching the axle all the time. Will that hurt the axle?

Not at all. Primarily, the total weight of the vehicle normally contacts the axle at a point under the leaf springs. The rubber spring, however, contacts the axle at a secondary point of contact. By adding a secondary point of contact we are reducing the stress at the original point and are spreading out the load to 4 points of contact on the axles instead of 2.

Furthermore, the progressive spring rate provides a soft uptake of the load rather than the sudden stop of a solid bump stop, providing a good ride with reduced stress.

I have a 1985 motorhome with a badly sagging rear suspension. Will Timbren's SES (suspension enhancement system) help?

Timbren's Suspension Enhancement System will certainly help, but our systems are designed to work in conjunction with a suspension that is in good condition. We recommend that the motorhome be inspected by a suspension specialist, to ensure the suspension is in good condition, prior to installing a Timbren system.

Can I haul more weight on my truck if I install Timbren's SES kit?

You cannot exceed the manufacturers axle rating or GVW rating of the vehicle. A Timbren suspension enhancement system will greatly enhance the performance of a heavily-loaded vehicle by adding to the spring rate. You can expect reduced sag, and improved roll stability.

How does Timbren's product compare to an air system? What are the advantages?

Here are 9 ways to compare Timbren's SES to an Air Ride system:

  1. Ride Quality: SES upgrades deliver a softer ride empty and loaded especially with extra-heavy loads
  2. Stability: SES upgrades eliminate roll and sway even with the heaviest loads
  3. Reliability: SES upgrades are made to last they will never start leaking air because there is no compressed air.
  4. Ease of use: SES upgrades require zero maintenance.
  5. Ease of installation: SES upgrades take less than an hour to install
  6. Price: The installed price of an SES upgrade is about 1/2 the installed price of an air system
  7. Warranty: SES upgrades come with two of the best warranties in the industry
  8. Lifetime warranty
  9. Customer Satisfaction Guarantee


  • 30498087
  • 809933011554
  • New


Shipping Information

  • Item Requires Shipping
  • 8.0 lbs.
  • W9.5000” x H5.5000” x L7.0000”
  • Free ground shipping (some exclusions may apply)


Customer Reviews

Comment Total Reviews (0)

Write the First Review!

You must login to post a review.