Proper Installation

  Spring Tension Chart  ·  Safety  ·  Warranty

How to get the best results for safe, smooth cargo door operation.
Cargo Systems recommends our spring assemblies only be installed, adjusted or modified by the original trailer manufacturer or an authorized dealer. Under no circumstances should the end user attempt to modify, adjust or replace a torsion spring assembly.

We require the weight of the door and door dimensions to determine the proper spring assembly system for your installation. We will help calculate the door weight, if needed to help determine which assembly is right for your application. Most springs are standard 2 diameter, however we also offer 2-5/8 diameter springs and 3-3/4 diameter springs.

We create specialized assemblies for doors with extra height, aluminum or steel tread plate, extra steel in the door or special flooring. We have customized assemblies to properly lift doors that are heavier (up to 600 lbs.), and 113 in height (or taller).


Proper installation is essential for safe, smooth operation.

  1. Measure inside trailer width. Cut spring tube to allow 1 clearance on both sides. Lay aside.
  2. Weld 1-1/2 x 2 x 3 mounting brackets to header. 1-1/2 inch leg welded. 2 leg projects into trailer. Allow 4 clearance between jamb and 2 mounting leg.
  3. Check cable drums drum stamped RH on curbside, drum stamped LH on driverside. Leave set screws loose.
  4. Bolt spring assembly onto mounting brackets with four 3/8 shoulder bolts provided. Galvanized bearing plates should be on outside of mounting angle, so that the shoulder of bolt fits in punched slot. Tighten four nuts securely. Stationary end of spring mounts on the curbside.
  5. Mount cable anchor bracket securely on ramp with through bolts. Center line of cable anchor pin should be a nominal 9 from top of ramp.
  6. Install cable stop in slot of cable drums.
  7. Check all nuts and bolts on mounting assembly for proper tightness.
  8. Clamp a vise grip on spring shaft at least 8 from end of spring. Vise grip will lie against header to stop shaft from turning.
  9. Wind loose cable onto drum start with RH (curbside) drum. Set cable taught and secure set screws. (Wind drums up toward ceiling.) Now set cable taught on LH drum and secure set screws. By starting with RH drum, cable slack will be minimized.
  10. Wind tension onto torsion spring with ramp open. Use only 1/2 winding bars designed to fully insert into casting. Caution should be exercised to see that bars are properly sized and seated before winding. An improper winding tool can rupture the casting and cause bodily harm. Wind spring down toward floor. Approximate turns required to balance various ramp heights: 66 = 8.6 turns, 72 = 9.3 turns, 78 = 9.9 turns, 84 = 10.6 turns, 90 = 11.3 turns, 96 = 12 turns, 102 = 12.7 turns, 108 = 13.4 turns.
  11. Remove vise grip from spring shaft.
  12. Check ramp for proper balance. Turns may be added or subtracted to achieve balance.

If more than one full turn over suggested turns are required, use a heavier model Ramp-Heister, because spring life will be severely shortened. Also, an over wound spring makes the ramp difficult to open.

Opening Height
Ramp-Heister cable assemblies are available in three lengths to allow for various opening heights: A cable (131) = up to 6-6, B cable (149) = up to 7-6, C cable (176) up to 90.

Door Weight
Ramp-Heister spring assemblies are designed for ramps of various weights, from 100- lb. through 600-lb. in 25-lb. increments. Always use the model designed for your door weight and height. If in doubt, or for any special situations, contact Cargo Systems at (574) 264-1600. Provide us with door width, height, and weight and we will provide springs for any special situation.

Color Coding
All Ramp-Heister springs are color coded and numbered.

Cargo Systems is a member of the National Association of Trailer Manufacturers (NATM).

Spring Tension Chart  ·  Safety  ·  Warranty