How to Rebuild Zipper Carnival Ride Brake Calipers

Too many times, the seal will give way in the zipper ride's brake system, leaking brake fluid all over the scenery, shutting the ride down until proper repairs have been done. Just as often, the maintenance person does not know how to rebuild the caliper sets, so when the calipers are put back into service, another mess and more down time for the ride. The following directions will take you through the proper procedures to follow when rebuilding the caliper sets.


  1. 1
    Place brake casing into a soft jawed vise with end plug (6) in a vertical position. Note that clamping should be done at the sides of the caliper on the machined surfaces.
  2. 2
    Remove bleeder screws (19), using a 7/16” socket and ratchet or box end wrench. If a combination wrench is used, do not use the open end of the wrench because it may strip the flats before loosening the bleeder screw.
  3. 3
    Remove hex nut (1) from compensator assembly (9), using a ½’ socket
  4. 4
    Remove belleville spring (2) wedge ring (3) washer (4) and o-ring (5) from compensator assembly (9).
  5. 5
    Using a spanner wrench, remove end plug (6) from housing ( 18)
  6. 6
    when removing the end plug (6) from the housing, the compensator assembly should remain in the piston. If it comes out with the end plug, this indicates that it had been assembled improperly.
  7. 7
    Remove piston (10) and lining (11) assembly from housing bore.
  8. 8
    Remove flat head screws (12) to separate lining (11) and piston (10). Save the lining for future use for replacement of worn linings which does not require full disassembly. This lining is still reusable. However, notice the quantity of rust and exfoliation which has accumulated between the piston and the lining. This rust as it built up actually caused pressure and contributed to the shearing of the upper right hand screw. Before this lining can be reused, it must be cleaned of all these oxide deposits, taking great care not to disrupt the ridge at the bottom where the lining seats into the piston. This area is where all of the braking force is exerted, and the aluminum screws will not shear if it is seated properly. Any movement of the lining in the piston under braking pressure will result in the screws being sheared.
  9. 9
    Notice that the right hand screw has been broken off. Notice as well the excessive amount of rust buildup under where the old lining had seated. This rust has allowed moisture to collect under the lining assembly, accelerating the corrosion process, weakening the aluminum screw due to galvanic effects, resulting in the screw having been sheared off. Before the new lining is assembled to this piston, the rust must be thoroughly removed, sealant will be applied to the new lining to act as a seal and adhesive, and new screws will be installed. Never reuse old screws.
  10. 10
    Remove compensator assembly (9) from piston (10), using an 11/16” open end wrench . Notice the use of a folded rag in the jaws of the vise to prevent damage to the piston .
  11. 11
    When the compensator assembly has been removed, carefully inspect the threads for damage, making sure that all old locktite material has been removed from the threads
  12. 12
    Remove o-ring (8) and backup ring (7) from end plug (6)
  13. 13
    Using a thin blade tool, or a pick tool, remove backup ring (14), o-ring (13), and seal (15) from housing bore.
  14. 14
    Remove flat head screws (16) and lining (17) from housing bore. Inspect the housing bore contact area for corrosion, and remove any which may be present.
  15. 15
    If the lining is in good shape, clean and set it aside as spare parts to be reused in the event that anther lining wears out. At this time, do not reuse the old linings because new ones are provided with the rebuild kit. This end plug is not reusable. Notice in the photo to the left that the center hole has been crushed by impact with a hammer or other object, and in the photo to the right, the edge where the o-ring and backup ring installs has severe pitting corrosion. The new pressure compensator will no longer fit into the center hole, and the new o-ring and backup ring will not make a proper seal against the pits left from the corrosion. The end plug in the photos to the left is reusable, and if properly cleaned will provide long service.
  16. 16
    Notice the white powdery substance along the perimeter of the threads. This is the anodizing which has been attacked by filiform corrosion. The anodizing or gold coloration was applied to act as a sacrificial anode, and the white powdery substance is the produce after corrosive attack. This is normal, and if the corrosion has not pitted the groove where the o-ring and backup ring seat, it will be all right. However, due to the fact that the protective anodizing has been compromised, the bare steel will now corrode under corrosive attack, and protective measures need to be undertaken.
  17. 17
    Using a mild wire brush and brake parts cleaner, or any other solvent which does not contain petroleum distillates, such as electrical parts cleaner, naptha, or isopropyl alcohol, thoroughly clean the entire end plug assembly. If using a flammable substance such as naphtha or isopropyl alcohol, be sure to work in a well-ventilated area, well away from sparks or flames, and for safety's sake, have a safety observer with a CO2 fire extinguisher standing nearby.
  18. 18
    Using a rounded object (in this instance a 6” ratchet extension), and 400 to 600 grit emery cloth, clean out the inside of the end plug. This area is where the pressure compensator makes its seal, and travel occurs within this area as the piston travels outward during normal liner wear. Normally, there is a small area of wear, where the anodizing has been worn away, with rust or oxide deposits in this area. If there is deep pitting in the wear area, the end plug cannot be reused, or leakage will occur past the pits. Use a folded rag to protect the machined surfaces from damage by the jaws of the vise. Note that brake fluid eats paint if it is left on a painted surface too long, and if brake fluid comes into contact with a customer’s clothing made of polymers, it will destroy them just as well.
    • When using a cylinder hone to clean out the bore of the housing, be careful not to hone down the threads inside the housing. Also, use the finest possible grit stone that can be obtained, normally only glaze breakers are available from most auto parts stores.
    • If a coarse glaze breaker has to be used, first smear grease onto the stones, so that the fine oxides removed from the inside of the housing will fill the pores of the stones, and make less abrasive. Doing this means that in the future, these stones will only be good for polishing and honing, so keep them separate from other stones used for rougher abrasive work. The finished product should be as close to mirror-like as possible when done.
    • If there are obvious signs of scratching from the hone, it is too rough, and should be used on something else to wear it down and smooth it more before final polishing of the housing. Adding grease will close the pores of the stones with the materials removed. For quickly wearing down a glaze breaker to smoother polishing, a piece of pipe, a tin can, or other rounded steel item can be used. It is easier to just purchase the proper stones in the first place, because any scratches put into the housing will have to be removed before going on with reassembly.
  19. 19
    Since usually one or more of the fastening screws for the lining will be sheared off, now the sheared off portion of the screw needs to be drilled out. These are 10-24 screws, so use a #25 drill bit to drill these out, and follow with a 10-24 tap to clean the threads. If the proper size drill bit is not available, do not substitute for any other size; these parts are expensive, and a #25 drill bit is very cheap. Do not use a 5/32 drill bit just because it is close to the same size and do not go to a smaller size drill bit, because the likelihood that the tap will break is increased when tapping the holes out. When drilling the holes, put the housing, or piston in a vise so that it will not move, and make sure that you drill straight down through the hole, using both hands, and keeping the drill steady. If it is a piston which is being drilled, use folded rags to protect the outer surface, and test its stability in the vise before beginning to drill to make sure the vise is tight enough, and the piston will not swivel sideways in the jaws. It is much more preferable to use a drill press, but sometimes they are not available. Use a 3/8” drill capable of at least 900 to 1000 rpm, do not use a ½’ drill. Most ½” drills are too slow in rpm, and have such high torque that they might break the drill bit off on breakthrough. Use a sharp drill bit, start the drill at high speed, but with very little downward pressure so it can start its way through the aluminum of the screw, and very slowly let the drill bit do all the work.
  20. 20
    Run a tap through the holes to clean out the threads. If drilling has been done, the old thread material needs to be removed. This thread material should be of aluminum, if someone in the past has not put steel screws into the part. Aluminum has a tendency to clog up the tap, so a lot of back and forth tapping should be done.
    • Turn the tap in just a little, then back it almost all the way out again, never putting more than just the minimum of torque on it each time it is turned in. This is a long tedious process, but if performed in this manner, it will prevent the tap from binding in the steel and breaking. When running the tap through the housing, the tap is traveling through almost ¾” of steel, and there is a very high likelihood of binding.
    • Use the tee handle in the tap set for this, and use wrist action to twist, do not use both hands on either handle as some persons prefer to do. By using wrist action and one hand, it makes sure that too much torque is not applied, and helps keep the torque straight down the axis of the tap, reducing the chance of breakage. If the tap breaks off inside the piston or the housing, then you have just ruined a very expensive part.
  21. 21
    Before installing the new lining into the housing, first double check to make sure the mating surface of the housing is well cleaned of all rust and debris. If necessary, scraping it will help, followed by a small wire brush and brake cleaner to remove all traces of oil and dirt.
  22. 22
    Mask off all the areas where paint will not be applied, and prime the area where the lining seats to protect it from corroding again.
  23. 23
    Set the housing aside for the paint to dry while working on the piston and compensator assembly.
  24. 24
    Carefully install new back-up ring (7) and o-ring (8) over non-threaded end of plug (6) and into groove. Make sure they are installed in proper position in groove.


  • Cleanliness is of the utmost importance, and attention to detail helps a lot.
  • If you have no idea as to how to use any of the tools listed above, then you shouldn't attempt this operation.


  • When using any flammable solvents, make sure to locate your work outside, and if possible, have a fire extinguisher handy.
  • When using chlorinated solvents such as brake pad cleaner, ensure that there is adequate ventilation.

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