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Timbren SES Suspension Enhancement System SKU# GMFK25D - Front Kit

Suspension Rubber Helper Spring Kit


This SES Suspension Upgrade fits the front suspension of a Chevrolet Silverado 2500HD/3500HD & GMC Sierra 2500/3500 truck. Our hollow rubber springs are engineered to deliver a progressive spring rate. In other words, the more weight that pushes down on the rubber springs (weight from a snowplow or heavy aftermarket accessories – such as a steel bumper) the harder they work to prevent front-end sag.

GMFK25D replaces the bumpstops on the front suspension of the 2011-2021 GMC Sierra and Chevy Silverado 2500HD and 3500HD pickup truck and cab and chassis models.

This kit is rated at 8000 lbs capacity. Even though you’re increasing the spring rate by adding this upgrade, this does not increase the GVWR (Gross Vehicle Weight Rating). Please make sure that the load does not exceed the GVWR set by the manufacturer.

Pricing: $297.00
5 5 1
Free ground shipping to lower 48 states (some exclusions may apply)


Timbren SES – Suspension Enhancement System – upgrades improve your suspension with:

More Safety

When extra weight makes your vehicle squat in the back, the front-end lifts up reducing traction on the front tires. Not only that, if the front is too high your headlights will shine up into the eyes of oncoming traffic instead of pointing down on the road ahead.

Timbren SES upgrades are designed to keep your vehicle level at all times. This will increase traction on the front tires, improve overall steering and keep your headlights pointing down on the road where they belong.

More Stability

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

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

More Comfort

Too much weight can cause your vehicle to bottom out if you’re driving over roads that are bumpy and rough. All this road shock will compromise an otherwise comfortable ride.

Improve your ride quality by installing Timbren SES upgrades, guaranteed to provide a softer, smoother ride… empty or loaded.



  • Eliminate Vehicle Squatting & Sagging
  • Cushion Road Shocks
  • Improve Handling
  • Satisfaction Guarantee
  • Lifetime Warranty


  • Rated for 8000lbs
  • Overall kit height = 3.25”

What's Included In The Box:

  • 4x Aeon® hollow rubber springs
  • 4x Rubber mounting spacers
  • All necessary hardware



"The Timbren SES system is the answer for rear end sag and soft handling." Larry V. - South Dakota

"My F-250 is awesome, now. Thanks to your Timbren SES system I don't have to worry about a 'sagging rear end'." Rick C. - New York

"I've put a Timbren SES kit on 2 different RAM 1500 trucks and would never tow anything without them ever again." Joel I. - Ontario, Canada


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


  • GMFK25D
  • GMFK25D
  • 809933005270
  • Timbren SES
  • New


Shipping Information

  • Item Requires Shipping
  • 4.0 lbs.
  • W9.5000” x H5.5000” x L7.0000”
  • Free ground shipping to lower 48 states (some exclusions may apply)


Customer Reviews

Comment Total Reviews (1)

Perfect Solution for vehicle sway and roll
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 month

Not purchased from: Timbren

Just installed the Timbren GMFK25D bump stops on the front of a 2015 Chevy 3500 dually. I needed some additional stability for the front for heavy loads and these will definitely give me what I need. The installation was more challenging than the directions make out but not impossible either. Getting the Timbrens back into the socket that the stock bump stops come out of requires some contortionist moves within the limited space available, and the use of the wood-block and soapy water as noted in the directions to get the Timbrens fully seated. I choose to not remove the front tires and had I done that, it might have been easier. The provided directions are more than adequate.

The front end of the truck is now slightly higher than it was with the stock bump stops installed and as a result, more level than before. The ride on rough surfaces is a bit stiffer, but on paving there was little if any noticeable difference in ride quality with the truck empty.

Drivability and handling seemed to be unaffected as well. The extra height and stiffness will be a welcome addition with the heavy slide-in camper that this vehicle hauls. The camper is a high-profile addition to the truck when it's loaded, and as a result, catches even the slightest amount of wind, especially side winds or when semi's pass. I expect that with the additional height and stiffness that I will experience much less vehicle sway and roll on windy days, especially with side winds.

Overall this is a very useful upgrade to this vehicle and will definitely provide the extra stiffness and roll and sway control that was lacking with the stock bump stops. The installation is challenging, however with some time and patience, and blocking for the truck while working under it to ensure safety, this is a doable and worthwhile project.

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