Although M-3 offers both single and dual systems, the dual system is recommended on doors weighing 120# or more.  The dual-spring system offers greater flexibility when balancing a ramp door.  Safety is another key issue.  Since both springs are mounted on a common shaft, if one should happen to break the second spring is still loaded.  This will not keep the door from falling but will slow the rate for descent.

A description of our standard dual spring system follows:

  • Standard tube length for 8’ and 102” trailers is 96”.  Tube length for 7’ wide trailers is 81” and 5’ wide and 6’ wide trailers are provided with a 66” tube and a single spring.
  • Standard dual spring weight is 160# for 8’ wide and 102” wide trailers.  We recommend 120# dual spring systems for 7’ wide trailers and a single 80# spring for 5’ wide and 6’ wide trailers.
  • All systems are provided with 5” diameter cable spools unless additional height is required.  At this point we will go to a 6” diameter spool to allow for more cable.  Please call for quotation on systems requiring additional height.
  • We also stock 185#. 205# and 250# dual spring systems.  Prices quoted above are for systems to 205#.  250# and above require a special quotation.
  • For orders of 25 or more, systems will be crated at no additional charge for LTL shipments.  Please specify your choice of carriers.
  • For orders of less than 25, the spring systems (to 205#) will be packaged two per box and shipped UPS.  Two spring systems (to 205#) can fit in each box.  Spring systems over 205# are shipped one per box.

*Door weight is established by simply lowering a finished door onto a bathroom scale before any lifting mechanism is installed.  We refer to this as “springing weight”.  By weighing a finished door we can more accurately balance the door.