GP Suspension 25mm Cartridge Kit

For Harley-Davidson Softail Models

Track-Tested, Street-Tuned

We've been building suspension for national-level racers for years. This kit takes that same technology and dials it in for street riding - not race-stiff, but properly controlled.

Engineered to Absorb Every Road Imperfection

Exceptional suspension begins with a hydraulic system capable of absorbing every imperfection on the road you travel. Through tireless refinement with professional racers, canyon carvers, and touring aficionados we've created a system that delivers amplified traction, heightened comfort, and above all—a ride that brings a genuine smile to your face.

What Makes Our Kit Different

Better Compression Control

Our valve design handles small bumps smoothly but firms up for bigger hits. No more choosing between comfort and control - you get both.

Proper Rebound Damping

Stock Softails bounce around after hitting bumps. Our rebound valving keeps the wheel planted and gives you actual control.

Topout Spring

Prevents harsh extension when the fork reaches full travel. Keeps the tire on the ground and eliminates the jarring feel when going over crests.

Progressive Bottom-Out

Instead of slamming into the stops like stock suspension, our system progressively controls the end of travel. You'll know you're at the limit without the harsh impact.

Manufactured & Built entirely in Ventura, CA. All machining and engineering work remains in-house—proudly American-made with decades of collaboration alongside top-tier racers.

Custom-Built for Your Ride

Each kit involves meticulous consideration of rider weight and individual riding style. Recognizing that proper setup is fundamental to exceptional suspension, we take immense pride in tailoring a kit specifically for every rider. Whether you seek luxuriously smooth rides on everyday bumpy roads or crave track-ready, precision-handling performance, we have the solution for you.

We recommend pairing our 13"-13.5" adjustable rear shock with all front cartridge length options for optimal geometry. 

Enhanced Performance & Length Options

• Travel increased: From 121mm to 125mm (optimized through extensive R&D)
• Three length options available:
  • Stock length (recommended setting your shock at 13")
  • +1" over (recommended setting your shock at 13.25")
  • +2" over (recommended setting your shock at 13.5")

Note: 2" over applications require extended brake lines for proper fitment. OEM chrome tubes can be used for all length options - our minimum standard of 6" overlap between upper and lower tubes is achieved even at 2" over

Full Adjustability at Your Fingertips

Located conveniently on your new fork cap:

• 30 clicks of compression adjustment
• 30 clicks of rebound adjustment
• 12 turns of preload

Set it and forget it, or fine-tune between rides—we're always a call away for setup support.

What's Included

Pricing includes custom spring set selected by our setup technician based on your riding information.

Transform your Softail with race-proven suspension engineering.