FORK SPRING PRELOAD
EXTERNAL TOP-OUT SPRING

DAMPING ROD or CARTRIDGE

Preload has a huge effect on the feel. Recommended Preload is available in Product Search or your DVS Setup Sheet.

Dirt bike - Fork preload is NOT a tuning variable. Too much preload will make the ride harsh particularly on acceleration bumps.

Street bike - Fork Preload can be used to affect ride height and chassis geometry. It can also temporarily be used for increased loads.

1 - These instructions cover all EXTERNAL TOP-OUT SPRING FORKS

"External top-out" means external to the damping rod or cartridge tube

This includes:

     All Damping Rod Forks

     Some right side up Cartridge Forks

Damping Rod with External Top-Out Spring

External Top-Out Cartridge

Internal Top-Out Spring - Click Here

2 - TOOLS AND SUPPLIES
  • Tape measure (metric)
  • Tubing cutter for spring preload spacer
  • Preload Spacer material
  • Steel Spring Washers

2 METHODS

METHOD 1 - Direct Measurement

DAMPING ROD

EXTERNAL TOP-OUT CARTRIDGE

3 - Setting the fork spring preload is done by making the correct length preload spacers.

  1. If your forks have Preload Adjusters set them to minimum.
  2. If you have a damping rod fork with an Emulator. Install the Emulator Adapter first if required. Drop the Emulator down the tube. It sits on top of the damping rod (or Adapter) with the Emulator Valve Spring facing up and is held in place with the main fork spring. Visually check to make sure the Emulator is sitting squarely on top of the damping rod or the Adapter.
  3. If you have a cartridge fork with an external top-out spring the cartridge rod does not need to be attached to the cap for this process.
  4. Extend the fork tube all the way.
  5. Insert the fork springs into the fork tube. (On top of the Emulator if used.)
  6. Install a steel or plastic fork spring washer or special collar.
  7. Install the fork spring spacer tube. Any length that goes above the top of the fork tube is ok for now.
  8. Install another steel or plastic fork spring washer or special collar.
  9. Set the fork cap on the washer.
  10. Measure from the top of the fork tube to the sealing lip on the fork cap. This is a direct measurement of fork spring preload.

Direct Measurement of Preload
(THIS ONE HAS WAAAAY TOO MUCH, we will need to cut the spacer)

  • 11. Adjust the spring spacer tube length to achieve the proper preload.
 
In this example using the image above:
For 15mm preload you would shorten the spacer by 31mm.
46 - 15 = 31mm shorter

 

 
NOTE: You must have steel washers on both ends of the spacer. The spacer must not rest directly on the spring or the cap.
 
NOTE: RT Springs are often a different length than stock. This is how they are designed. You will have to make your own custom spacers.

METHOD 2 - Calculate

4 - Be sure to check if the thread on the cap hits the thread in the fork tube before touching the washer. This would give a false reading. If this occurs, temporarily add spacing washers until it clears.

Measure from the spring washer to the top of the fork tube. Click the image to zoom in. You'll see it is 11mm.

5 -  Measure the Fork Cap Height

In this case 18mm. (The fork cap is upside down)

 

Calculate the Preload

(Fork Cap Height) - (Spring Washer to Top of Tube) = Preload

18 - 11 = 7mm Preload

Adjust the Spacer Length or add washers to get the recommended Preload.

NOTE: You must have steel washers on both ends of the spacer. The spacer must not rest directly on the spring or the cap.
 
NOTE: RT Springs are often a different length than stock. This is how they are designed. You will have to make your own custom spacers.