Sorbothane Installation Instructions

This article will explain how to install our Sorbothane Pad.


  • Cyanoacrylate glue (super glue)
  • Sand paper
  • washing up liquid/detergent
  • Scrubbing brush/old toothbrush
  • Sharp knife
  • Scribe (optional)

Installing your sorbothane pad is easy. Once you have made sure that the piston will rest at the correct position, the sorbo pad simply glues on to the cylinder head.

Step 1 

  • Remove the gearbox from the AEG.
  • Disassemble the gearbox, removing everything but the sector gear, cylinder, cylinder head, piston and piston head.
  • Slide the piston all the way to the front of the cylinder.
  • Rotate the sector gear anti-clockwise until the first tooth touches the piston's first tooth. This is the current angle of engagement (AOE) - the angle at which the first sector gear tooth engages the first piston tooth.
In most AEGs, the AOE is completely wrong and needs to be corrected


Step 2 - Mark the current piston position

  • Take a knife/scribe and mark the gearbox shell in line with the back of the piston - This makes it easy to reference the original piston position. 
  • If you use a marker pen to colour the area first, the line will be easier to see.


Step 3 - Find the correct angle of engagement

  • Rotate the sector gear until the first gear tooth and the first piston tooth are touching.
  • Now continue to rotate the sector gear until the two teeth make full contact.
  • This is the position at which the piston should stop at the end of each cycle.
  • Mark the gearbox again at the new position.


Step 4 - Test fit the sorbo pad

  • Put the sorbo pad into the cylinder and make it lie flat on the cylinder head
  • Insert the piston and slide it all the way forward.
  • If the back of the piston lines up with the second line you made in the previous step, you are ready to glue the sorbo onto the cylinder head.
  • In most cases, the piston will be too far back - this is because some material needs to be removed from the cylinder head.


Step 5 - Prepare the cylinder head

  • Most cylinder heads come with a hard rubber pad which needs to be removed in order to allow correct AOE.


Step 6 - Make another test fit

  • Before gluing, do another test fit like in Step 4. The back of the piston should line up with the second line you made on the gearbox shell.
  • When the gearbox is fully assembled, the spring constantly pushes on the piston. This slightly compresses the sorbo pad, so the piston's actual resting position will be slightly further forward.
  • If the piston is still too far back, you may need to remove some material from the cylinder head, or buy a new one.
  • If the piston is not far back enough, you can add some thin shims/washers between the piston head and piston body.
  • Once you are happy with the piston position, you are ready to glue the sorbo pad onto the cylinder head.
You will need to remove the piston teeth that are in the way of the sector gear. A sharp knife, file or dremel are suitable for this.


Step 7 - Prepare the cylinder head and sorbo pad for gluing

  • Gluing is all about surface prep. The aim is to obtain a perfectly clean and dry surface.
  • Take your time here - good surface prep will ensure that the sorbo pad never comes loose, which could spell disaster for your gearbox.
  • Use a scribe or a sharp knife and carefully score the cylinder head.
  • Use rough sand paper to remove any semi-loose particles.
  • Wash the cylinder head and sorbo pad thoroughly with soapy water to remove any grease and loose particles.
  • Dry the sorbo pad and cylinder head with a lint-free cloth, allow to dry naturally, or blot with clean printer paper.


Step 8 - Glue the sorbo pad to the cylinder head

  • Apply a thin, even layer of glue to the cylinder head, but don't put too much glue around the hole.
  • Carefully position the pad as central as possible. It doesn't have to be perfect, but the holes in the middle must line up.
  • Apply gentle, even pressure to the pad. You should feel the pad compress very slightly. A small block of wood makes it easier but you can use any flat surface.
  • After about 30 seconds you can let go.
  • Use a cotton bud or similar to remove any excess glue from the hole.
  • Leave the glue to harden for at least 2 hours before use.



Congratulations, you are done!