How to rebuild your brake caliper


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How to rebuild your brake caliper

Postby WingAdmin » Fri Oct 09, 2015 2:48 pm



"Rebuilding a caliper" - it sounds complex and involved. It's not really. A brake caliper has only two real parts: a piece of metal with two holes in it, and pistons that fit into the holes. Brake fluid gets pumped into the caliper, and the pressure of this fluid pushes the pistons out. The pistons push against the brake pads, which in turn push against the brake rotor (disc), which slows the motorcycle down.

There has to be a seal between the caliper and the pistons, to prevent brake fluid from squirting out between them. These are rubber rings that fit into the caliper. Rebuilding the caliper consists primarily of replacing these seals and cleaning everything out.

Two things can indicate a caliper is in need of rebuilding: leaking brake fluid, or binding pistons. If the pistons are not able to retract properly, or the caliper is not sliding correctly, it will wear through pads quickly. A sure indication is when one of the two brake pads wears much more quickly than the other, or if brake pads wear out in a very short amount of time. If one piston is bound up, brake pads will wear unevenly, wearing thin on one end while the other is hardly worn at all.

In this How-To, we will be demonstrating the rebuilding of the rear brake caliper. Rebuilding a front caliper is an almost identical process - the main difference is how you get to the caliper.

To start with, we will need a caliper rebuild kit. This consists of all the rubber pieces that we will be replacing.

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Unless the brake pads are brand new (or almost new), this is a great time to replace them as well. I strongly suggest the use of OEM Honda brake pads. In my experience, aftermarket pads simply do not perform as well, and produce much more brake dust - which means your wheels are constantly black and filthy.

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We will also need brake cleaner. I tend to buy large quantities of brake cleaner at my local NAPA every time it's on sale, because I use it for many things other than just brakes -it's an excellent multipurpose solvent. It even lifts oil spills off of concrete garage floors!

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Lastly, we will need some high-temperature grease or lubricant, intended for use on brake parts. Regular grease should not be used - it will melt and burn at the temperatures found in braking systems.

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1. In order to get to the rear brake caliper, we must first remove the left saddlebag. Start with the motorcycle on its center stand. Remove both side covers, and if required, remove the seat. The bottom cover of the trunk must be removed. There are four recessed screws along the bottom, near the outer lip. In this picture, I am removing the leftmost screw. Remove all four screws.

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2. Gently slide the left side of the lower trunk cover backward to disengage it from the tabs on the bottom of the trunk sidelight/reflector. Be careful, as these tabs are fairly brittle, and easily broken if forced.

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3. Pull the tab at the front of the lower trunk cover free from the antenna frame. Repeat the process to free the right side of the lower trunk cover as well.

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4. With the sides of the lower trunk cover free, slide the cover forward so that it is no longer held in place by the trunk and saddlebag release levers.

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5. Once free of the release levers, lower the lower trunk cover and put it aside somewhere soft where the paint won't be scratched.

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6. There are two screw/trim covers that must be removed. They are removed simply by prying them away with your fingernail, or a small, thin, flat-blade screwdriver. They should be tight - if they are loose, it's a good idea to give them a slight gentle squeeze with a pair of pliers to make sure they grip the trim tightly. They can be easily lost if they are not tight enough. The first cover is on the back of the bike.

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7. The other one is on the left side, just a few inches from the back of the bike.

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8. Remove the screws exposed by each of the screw/trim covers.

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9. Once the two screws are removed, the lower rear saddlebag cover can be removed. Set it aside.

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10. Wiring for the lights will be exposed by the removal of the lower rear saddlebag cover. You may have a simple 3P connector such as the one I am holding, or you could have a rats nest of aftermarket wiring such as is shown in the top of the image. I decided after seeing this mess of wires and vampire clips to cut out and replace all of this wiring. These connectors connect the lights on the saddlebag to the bike's wiring. Because we're removing the saddlebags, these wires need to be disconnected.

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11. Open the left saddlebag. Inside the saddlebag, at the top, near the rear of the bag, you will find the release mechanism. It consists of a cable, connected to a nylon piece that snaps over the metal release bar. Unsnap the nylon piece from the bar.

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12. Rotate the nylon piece on the cable, and pull the cable free through the slot. Set aside the nylon piece.

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13. Here you can see the end of the release cable after the nylon piece has been removed. Squeeze the four locking tabs surrounding the cable and push it through the hole.

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14. Remove the four bolts fastening the saddlebag to the frame.

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15. Here you can see the saddlebag with the bolts removed. The large circle on the left is an adhesive rubber patch that can be removed to gain access to the rear brake caliper, in order to bleed the caliper without first having to remove the saddlebag.

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16. Tip the top of the saddlebag outward and make sure the release cable has come fully out of the bag.

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17. gently lift the saddlebag away from the motorcycle. Here you can see the emergency release button on the top of the saddlebag that is accessed from inside the trunk.

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18. You will now see the rear brake caliper exposed. Now is a good time to hose down the whole area with brake cleaner, to get rid of the grease and grime.

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19. Loosen and remove the banjo bolt on the caliper. There are two copper crush washers - one on each side of the brake line fitting. So one washer between the brake line and the caliper, and the other one between the bolt and the brake line. Don't lose these!

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20. Be prepared for a few drops of brake fluid to come out. I usually take a plastic bag, throw the banjo bolt and crush washers in it, and zip-tie it around the end of the brake line, so that it doesn't leak all over the floor while we work on the caliper.

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21. Loosen and remove the caliper bolts.

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22. Once the top one has been removed, remove the bottom one. If you do the bottom one first, you will have difficulty preventing the caliper from rotating when loosening the top one.

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23. Remove the caliper from its bracket. You may need to rock it back and forth slightly to retract the pistons enough to allow the brake pads to come free of the brake rotor.

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24. We're now working on a workbench. Remove the brake pad pin retaining bracket bolt.

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25. Once the bolt is removed, remove the brake pad pin retaining bracket. This bracket keeps the pins that hold the pads in place from coming loose.

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26. Once the bracket is removed, knock the brake pad retaining pins free and remove them.

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27. Remove the brake pads. You can see these aftermarket EBC brake pads are in sad shape, even though they are nowhere near worn out. They have fractured and are starting to crumble at the edges.

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28. Next we have to remove the pistons. If your caliper is in need of rebuilding, chances are the pistons will be bound up so tightly that they can not easily be removed. The surface of the calipers must be smooth in order to maintain a seal, so don't attempt to clamp on them with a pair of pliers and wiggle them out! Instead, we will take the caliper along with one of the brake pads back to the bike. Insert a brake pad into the caliper as shown, and temporarily hook the brake line back up to the caliper.

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29. Start pumping the brake. Brake fluid will pump into the caliper, pushing the pistons out. Usually one is much more stuck than the other, and will come out first.

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30. One piston will normally come out as shown until it contacts the brake pad, at which time the other will start coming out. You will be pumping a lot of brake fluid into the caliper in order to do this, so ensure you keep your brake fluid reservoir topped up - you don't want to have it run dry and start pumping air into the brake system as a result!

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31. Once both pistons are fully extended and have contacted the brake pad, disconnect the brake line from the caliper once more. Remove the brake pad and pull the pistons straight out of the caliper - they will come out quite easily.

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Note the white goo in the bottom of this cylinder. This is the effect of brake fluid that is not flushed often enough. The brake fluid is highly hydrophilic, which means it absorbs moisture out of the air. This moisture mixes with the brake fluid and eventually migrates down to the caliper, as it is heavier than brake fluid. It turns into this white emulsion. This is the primary cause of corrosion in brake calipers. Flushing your brake system at most every two years will prevent this from occurring.

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32. Back on the workbench with the pistons removed, it's time to start the rebuild process.

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33. Remove the brake anti-squeal spring, clean it with brake cleaner and set it aside - we will be reusing this.

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34. Using brake cleaner, spray out the caliper to remove all remaining brake fluid from the caliper and the cylinders.

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35. After spraying off the pistons, you can see a fair bit of corrosion. This corrosion must be removed, or it will compromise the new caliper seals. The piston wall needs to be as smooth as possible. If the pistons are so corroded that they are not salvageable, I would highly recommend replacement stainless steel pistons from Wingovations.

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36. Use very high grit sandpaper to recondition and polish the piston walls - this 1500 grit sandpaper is excellent. If they are in very bad shape, you could start with a 600 grit sandpaper followed by 1500 grit.

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37. When polishing, always move in a circular motion - never up and down or side to side. You don't want to lay linear marks into the piston. I find it easier to lay the sandpaper on my leg and move the piston over it in a circular motion while slowly rotating the piston.

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38. Once polished, the corrosion should be removed. Very minor pitting may remain, but if the pitting is too bad, the piston should be replaced.

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39. The pin collar is a sealed piece that should be able to slide easily back and forth within the caliper. Its purpose is to allow the caliper to self-center over the brake rotor as the pads wear. If this collar is seized, you will find one pad (usually the outside pad) will wear much faster than the other (inside) pad.

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40. Push the collar to one side, to extend one of the boots.

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41. Using small pliers, pull the lip of the boot from the groove of the collar, pulling the boot over the end of the collar. The collar itself holds the boot in the caliper, so don't try to pull it free yet.

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42. Once the outer boot is free of the collar, push the collar through the caliper. It will come free of the other boot as it does so.

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43. You can clearly see the groove that holds the boots in place as it is pushed free.

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44. This collar has significant corrosion, and was bound up enough that it was causing problems with the caliper.

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45. Squeeze the collar boots and remove them from the caliper. Discard the old boots.

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46. I used a wire brush to clean the corrosion off this collar, followed by a gentle polishing with 600 grit sandpaper.

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47. This collar still has pitting, but it is serviceable. It will likely need to be replaced the next time this caliper is rebuilt.

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48. Clean out the grooves in the caliper. I use a small allen key for this - it allows you to easily access the groove and scrape corrosion and dirt out. Several sprays of brake cleaner help with this as well.

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49. Here you can see the corrosion being scraped from this groove. The grooves should be as clean, smooth and free of corrosion, deposits and dirt as possible.

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50. Remove the brake bleeder nipple from the caliper. Spray the area with brake cleaner to remove any remnants of brake fluid.

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51. Clean the nipple of corrosion and brake fluid deposits. Discard the old bleeder cap.

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52. Using a small screwdriver, very gently remove the upper seal from each cylinder. It is of the utmost importance that the insides of the cylinders are not scratched during this procedure.

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53. Pull the upper seals free and discard. Note that the upper seals are thinner and have ridges on the insides.

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54. Remove the thicker lower seals in the same manner.

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55. After thoroughly spraying the seal grooves with brake cleaner, all dirt, deposits and corrosion must be removed. It is very important that ALL corrosion and deposits are removed, so take your time and be exacting in this process. Any deposits left in the groove will push the new seals out of position and can cause leaks. Regularly spray out the grooves as you do this to clean out what you have scraped. Again, be very careful not to scratch the inner walls of the cylinders.

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56. If there is corrosion or deposits between the seals, they can be removed by very gently scraping with 1500 grit sandpaper or a small piece of Scotchbrite sponge. When this is completed and you are happy with the condition of the caliper, use brake cleaner to spray out the entire caliper - spray into the bleed nipple hole, the brake line fitting hole, and both piston cylinders. The caliper should be spotlessly clean!

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57. Identify the new lower seals - they are thicker, and do not have ridges on their insides.

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58. Coat the seal with brake fluid for lubrication, and push it into the lower slot.

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59. Note the upper seal is thinner, and has ridges on the inside of it. Coat it with brake fluid and install it into the upper slot the same way you did with the lower seal. Make sure the seal does not twist when installed, and that the ridges point inward.

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60. Once the seals are installed, inspect your work. Ensure both seals are fully and uniformly seated in their grooves and are not twisted. Coat the exposed surfaces of the seals with brake fluid.

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61. Coat the outer surface of a brake piston with brake fluid, and place it at the entrance to the cylinder, with the open end facing outward. Making sure it is absolutely perpendicular to the surface, slowly push the piston into the cylinder. Do not allow the piston to tilt, or it will bind, possibly gouging the side of the piston.

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62. Both pistons should push fully into their cylinders with relatively little resistance.

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63. Apply brake grease/lubricant to the inside of the collar housing on the caliper.

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64. Apply the lubricant to the inside of the new collar boots.

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65. Squeeze the piston-side slide boot and insert it into the caliper. Make sure it is securely inside the groove in the caliper.

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66. You may need to gently push the last bit of it in with a flat blade screwdriver in order to get it to properly seat.

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67. Coat the collar in lubricant.

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68. Push the collar into the large end of the remaining boot and push it almost all the way through so that the boot hangs off the end as shown. Don't push the collar so far that the boot slips into the groove on the end of the collar.

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69. Insert the end of the boot into the caliper, seating it into the groove.

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70. Once the boot is securely in the caliper, push the collar into the caliper.

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71. Seat the outer ends of the boots into the grooves in the collar and gently push it back and forth to make sure it is fully inserted and correct. Use brake fluid to spray all the grease off of the outside of the boots and anywhere else on the caliper it may have gotten.

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72. Put the new bleeder cap on the bleeder as shown and reinstall it into the caliper finger tight.

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73. Push the anti-squeal spring into place, and make sure its ends lock securely into the caliper.

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74. Apply grease to the pad retaining pins and spread it over the surface of the pins.

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75. Make sure your hands are free of grease or brake fluid, and insert the brake pads into the caliper. Push the pin retaining pins into the caliper, and through the holes in the pads. You will have to push the pads down against the anti-squeal spring in order to allow the pins through.

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76. Install the pin retention plate and torque the plate bolt to 8 ft-lb.

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77. Remove the old caliper bracket boot and spray out the cavity with brake cleaner. Lubricate the cavity and the inside of the replacement boot with grease.

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78. Insert the new boot into the caliper bracket.

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79. Place the caliper back over the brake rotor, making sure the brake pads straddle the rotor. Make sure not to displace the caliper boot you just installed in the previous step.

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80. Use brake grease to lubricate the smooth portions of the caliper mounting bolts. The upper caliper mounting bolt actually screws into the caliper itself, and the smooth pin portion of the bolt slides into the boot on the caliper mounting bracket.

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81. Insert and tighten the upper and lower caliper mounting bolts. The upper caliper mounting bolt/pin is torqued to 20 ft-lb, and the lower one is torqued to 12 ft-lb.

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82. Reattach the brake line fitting with the banjo bolt, making sure there is a copper crush washer on either side of the brake line. It should go: caliper, crush washer, brake line, crush washer, banjo bolt. Torque the banjo bolt to 25 ft-lb.

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83. Bleed the brake system, first bleeding the left front caliper, then the rear caliper.

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84. Ensure the rear brake reservoir is topped up while bleeding - it can take a fair amount of fluid to remove all of the air from the linked brake system, and this can easily empty the reservoir, sucking more air into the system. After bleeding, pump the brake pedal several times until resistance is felt - this will move the pistons out of the caliper and push the pads against the brake rotor. After this is done, top up the reservoir one more time.

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85. Spray the caliper and brake rotor with brake cleaner to thoroughly clean any leftover grease.

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86. Replace the saddlebag.

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87. Before pushing the saddlebag fully into position, make sure to push the release cable securely into its hole.

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88. Bolt the saddlebag into place with the four bolts.

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89. Thread the nylon piece onto the release cable, then snap it onto the release bar.

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90. Reconnect the tail/brake wire connectors.

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91. Replace the lower rear saddlebag cover. There are round, molded pins on the cover that seat into holes in the existing plastic - make sure they seat correctly, or the cover will not fully fasten in place.

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92. Replace the screws fastening the cover in place.

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93. Push the trim clips back into place. Make sure they are tight - if not, clamp them gently with a pair of pliers to make sure they do not fall off.

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94. Lift the lower trunk cover into place. Push it forward to clear the fronts of the release levers, then pull it up and back over the top of the levers.

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95. Fastening the lower trunk cover in place takes a bit of finesse - and practice. Position the cover so that ALL of the tabs on both sides are lined up, then push the cover up and forward to lock it into place. You'll find that if you attempt to do one side at a time, the process of locking one side in place will often unlock the other side - an exercise in frustration. Keep in mind the fragile, brittle nature of the tabs!

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96. Replace the four screws holding the lower trunk cover in place.

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97. Always make sure to take a careful test ride in a safe area whenever work on brake systems have been performed. Make several firm stops to ensure the new brake pads are fully seated.



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