I removed my rear brake caliper for the first time, and found this white soft-to-the-touch padding on the screws. What is it? It was quite difficult to remove the screws and this must have been the reason. The caliper was mounted with an adapter but there was only a single screw to hold both the caliper and adapter to the frame.

enter image description here

More importantly, can the screws be re-used in their current state, or does this "padding" need to be replaced?

Note: I am not asking about the red and blue threadlocker at the end of the screws, but the white stuff in the middle.

Update: I found an image of this part, showing the same white foam on the screws: https://www.bike-components.de/en/Magura/Disc-Brake-Adapter-for-180-mm-Rotors-p63867/#product-image-6

  • Can't find a good tag for this question, please re-tag as appropriate.
    – Szabolcs
    Commented Jun 26, 2022 at 12:17
  • 1
    Maybe a thread locker of some kind. Is it soft like handlebar tape foam, or more rigid like the outer brake casings plastic?
    – Robert
    Commented Jun 26, 2022 at 12:30
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    @Robert In the photo it's not very visible, but there was actually normal threadlocker on it as well. The top one in the photo has red, the bottom one blue.
    – Szabolcs
    Commented Jun 26, 2022 at 12:32

2 Answers 2


Re-answer (based on Szabolics' link in the comments):

It appears to be either a (now weathered/aged) moisture seal to prevent water from getting into the caliper mounting threads OR a a crude alignment aid when initially installing the caliper.

  • 1
    I was not asking about the blue residue at the end. I am familiar with that. I am asking about big white blobs in the middle. BTW whatever it is, it is manufacturer-applied. This screw has not been undone after the bike was purchased (until now).
    – Szabolcs
    Commented Jun 26, 2022 at 15:45
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    I found a picture of the part online (or perhaps a similar part), and it seems that these are always present on the screws: tnc-hamburg.com/TNC-Shop/Scheibenbremsen/Adapter/Magura-Adapter/…
    – Szabolcs
    Commented Jun 26, 2022 at 15:47
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    Sorry about the unclear question. I tried to make it clearer to avoid further misunderstandings. Would you just re-use such a screw or would you try to replace that white stuff?
    – Szabolcs
    Commented Jun 26, 2022 at 16:06
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    @Szabolcs, no problem at all! I would just re-use the original screws/bolts. Maybe a dab of blue Loctite on each of you have some, but that is optional. Keep an eye on it for a few rides to ensure they are still tight. If you have a torque-spec to follow then abide by that as well. Ride on!
    – Ted Hohl
    Commented Jun 26, 2022 at 16:15
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    Crude alignment, +1. I thought they were shipping retainers for keeping the washers on (nope). OP has a pic of a new set, showing them in the same place. If they were for moisture the OP's would've been squished up against the washer. Since they never move, then they fit in a hole large enough for them, which means w/o them you can cross thread too easily.
    – Mazura
    Commented Jun 26, 2022 at 23:20

I think it is a type of "loctite" paste that prevents screws from working loose during use , vibration , heat , cold etc.. Leave it on and reuse it when fitting the screws back again. Make sure screws are tight but do not overtighten.

  • No, the Loctite is visible near the tip (red, blue) and sits in the thread. The white stuff is odd
    – Chris H
    Commented Jun 27, 2022 at 9:23

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