Timbren 2011-2023 GMC/Chevy 2500/3500 Custom Specs for GMRCK25D

Eliminate Rear Sag and Protect Your 2011-2023 Silverado or Sierra HD Under Heavy Loads with the Timbren GMRCK25DM1

The Timbren GMRCK25DM1 is a rear suspension enhancement system (SES) bump stop upgrade for the 2011-2023 Chevrolet Silverado 2500HD, Silverado 3500HD, GMC Sierra 2500HD, and Sierra 3500HD in both 2WD and 4WD configurations.

It replaces the factory jounce stop on the frame with a purpose-engineered hollow rubber spring that engages progressively as load increases, preventing rear sag and controlling axle travel under heavy payloads and trailer tongue weight. Unlike traditional bump stops that only engage at the limits of suspension travel, the Timbren SES design contacts the axle in the normal travel range under load, providing a supplemental spring effect that works alongside the factory coil or leaf springs without requiring disassembly of the suspension. 

The GMRCK25DM1 includes a 1-inch custom spacer for applications requiring additional preload or gap adjustment to achieve the correct half-inch to one-and-a-half-inch unloaded gap between the rubber spring and axle. Rated at 8,600 lbs capacity, it is engineered for trucks regularly used for towing, payload hauling, and commercial applications. Made in Canada.

Key Features

• Replaces factory jounce stop with progressive hollow rubber spring for supplemental load support
• Prevents rear sag and controls axle travel under heavy payloads and trailer tongue weight
• Progressive spring rate increases resistance as load increases for automatic load leveling effect
• Engages within normal suspension travel range under load, not just at full compression
• Includes 1-inch custom spacer for preload and gap adjustment
• Rated at 8,600 lbs capacity
• 2WD and 4WD compatible for 2011-2023 Chevy Silverado and GMC Sierra 2500HD and 3500HD
• No disassembly of factory suspension required for installation
• Made in Canada by Timbren

Vehicle Fitment

Specifications

What's Included

• 2x Timbren hollow rubber progressive rate spring bump stops (left and right)
• 1-inch custom spacers
• Hardware for installation

About Timbren

Timbren Industries is a Canadian manufacturer of suspension enhancement systems trusted by truck and van operators across North America for payload and towing load control. The Timbren SES product line is engineered for direct bolt-on fitment on a wide range of light truck, van, and SUV platforms, replacing factory bump stops with progressive hollow rubber springs that provide an automatic load-leveling effect without the air compressors, sensors, or maintenance requirements of air suspension systems.

Related Parts on Our Site

• Timbren GMRCK25DM1.5 2011-2023 Chevy GMC 2500 3500 Rear Bump Stop 1.5-Inch Spacer - Same kit with a 1.5-inch spacer for additional preload adjustment

Frequently Asked Questions

What is the Timbren GMRCK25DM1?

The Timbren GMRCK25DM1 is a rear suspension enhancement system (SES) upgrade for the 2011-2023 Chevrolet Silverado and GMC Sierra 2500HD and 3500HD. It replaces the factory rear jounce stops with progressive hollow rubber springs rated at 8,600 lbs to eliminate rear sag and control axle travel under heavy loads. The M1 suffix indicates the kit includes a 1-inch custom spacer for gap adjustment.

What is the difference between GMRCK25DM1 and GMRCK25DM1.5?

The GMRCK25DM1 includes a 1-inch spacer and the GMRCK25DM1.5 includes a 1.5-inch spacer. The spacer thickness adjusts the height and preload of the rubber spring relative to the axle. If your truck's unloaded gap between the bump stop and axle is greater than 1.5 inches, the larger spacer helps achieve the required half-inch to one-and-a-half-inch gap for correct operation. Timbren recommends measuring your specific gap before selecting the spacer size.

Does the Timbren GMRCK25DM1 increase my truck's GVWR?

No. Adding the Timbren SES does not increase the Gross Vehicle Weight Rating of your 2500HD or 3500HD. The GVWR is set by the vehicle manufacturer and is unchanged by this upgrade. The Timbren system improves load control and reduces sag, but the vehicle must not be loaded beyond its rated GVWR regardless of the suspension upgrade installed.

Will the Timbren SES affect my ride quality when the truck is empty?

The Timbren SES is designed with a half-inch to one-and-a-half-inch gap between the rubber spring and the axle when the truck is unloaded. This gap means the rubber spring is not in contact with the axle during light driving, so the ride quality on an empty truck is not significantly affected. Once a load is applied and the suspension compresses enough to close the gap, the Timbren spring engages progressively to resist further sag.

Is the Timbren GMRCK25DM1 compatible with factory lift or leveling kits?

The GMRCK25DM1 is engineered for stock ride height 2011-2023 Silverado and Sierra 2500HD and 3500HD trucks. Timbren recommends confirming the unloaded gap between the rubber spring and the axle falls within the half-inch to one-and-a-half-inch specification after any lift or leveling kit installation before ordering. The M1 or M1.5 spacer selection may need to change depending on how the lift affects that gap.

Does the GMRCK25DM1 require any modification to the truck?

No. The Timbren GMRCK25DM1 is a direct bolt-on replacement for the factory jounce stops. It requires no cutting, welding, or modification to the frame, axle, or suspension components. Standard hand tools are sufficient for installation.

How does the Timbren SES compare to helper springs or air bags?

The Timbren SES offers a maintenance-free alternative to helper leaf springs and air bag systems. Unlike air bags, the Timbren rubber spring requires no air compressor, no sensors, no lines, and no regular maintenance. Unlike helper springs, the progressive rubber design allows normal ride quality when unloaded. The trade-off is that Timbren does not allow adjustable load leveling the way an air bag system does, but for most hauling and towing applications the Timbren provides a simpler and equally effective solution.

Does the GMRCK25DM1 fit the cab and chassis 3500HD variants?

Yes. The Timbren GMRCK25DM1 is compatible with the 2011-2023 Chevrolet Silverado 3500HD Cab and Chassis and the GMC Sierra 3500HD Cab and Chassis in addition to standard pickup configurations, in both 2WD and 4WD drivetrain configurations.

Installation Instructions

1. Safely lift the rear of the vehicle and support it on jack stands. Verify the rear axle is supported and the vehicle is stable before beginning.
2. Locate the factory jounce stop on the frame rail above the rear axle on each side.
3. Remove the factory jounce stop by unbolting it from the frame bracket. Note the orientation and hardware for reference.
4. Measure the gap between the mounting surface and the top of the rear axle with the suspension at ride height to confirm spacer selection. The installed Timbren spring should produce a half-inch to one-and-a-half-inch gap between the bottom of the rubber spring and the axle pad with the truck empty.
5. Install the 1-inch spacer onto the Timbren mount bracket as needed to achieve the correct gap.
6. Position the Timbren GMRCK25DM1 onto the frame bracket and install using the provided hardware.
7. Torque to the specification provided in the Timbren installation instructions included with the kit.
8. Repeat for the opposite side.
9. Lower the vehicle and verify the unloaded gap between the rubber spring and axle pad is within the half-inch to one-and-a-half-inch specification on both sides.
10. Load the vehicle to a typical working load and verify rear sag is controlled and the truck sits level.