I have a submission to be added to the Unofficial Manual to do with the Front Brake Pad changing process for my 2018 DS (so all models under the 2015+ S Platform section).
The situation is that I was changing the front pads which were slightly worn and a stainless steel spring plate fell out of the caliper when I dropped the right pad after not getting the left one all the way seated. It was not mentioned in the manual so I started making records. In addition there were some stainless steel side plates on the outsides of the stock pads which I had no idea whether to move over to the new pads or discard.
In the process of making inquiries on the Facebook group, I was told or found the following...
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1. The stock Front pads may be fitted with stainless steel shims that are held onto the outside of the pads by four small folded clips. These are called anti-squeal shims and should be carefully removed, cleaned and transferred to the new pads in the same orientation. A light coating of copper anti-seize grease to both the outside of the pads themselves and the anti-squeal shims is advised.
2. When removing lightly worn pads without taking the caliper off first it is possible to dislodge a stainless steel rectangular spring from the top of the caliper body. If this drops out, the caliper must be removed according to normal instructions to refit the spring. It is an anti-rattle spring and exerts a small amount of spring pressure on the top surface of the pads to prevent rattling when riding on rough surfaces.
Take the opportunity to clean the spring. Hold the caliper in your hand with the rotor slot facing up towards you and the pad locking bolt at the front. You will see the caliper body has three sections of metal between the two sides. The loose spring only fits on the rear-most one. Note the two small folded lugs on the spring and place those face down into the body of the caliper. There is also another steel clip at the very back which is usually more firmly attached. It has a small lip visible on it (indicated in picture) and the back edge of the loose anti-rattle clip should go under this lip.
Replace the pair of pads and hold them in position with the pad locking bolt. In this position, the pads themselves hold the anti-rattle spring in place properly. You may now replace the caliper as per standard instructions (remembering the pad locking c-clip). Clean the rotor with IPA or brake cleaner and pump the front brake lever a fair few times to build back up the hydraulic pressure. Test braking in a safe area through low to mid speed controlled stops before progressing to mid to high speed emergency stops.