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Recently I wanted to remove the brake pads of my Shimano 105 disk brakes to check their wear state. When I was about to open the screw which holds them in place I found that some white crust had accumulated on the screw - possibly remains from my winter rides. As I tried to open the screw on the rear wheel brake with a screw driver at some rather moderate force (how much torque can you supply with a simple screw driver...) the head of the screw did just shear off, leaving the rest of the screw in place without any possibility to grab or otherwise move it (see images at the end of this post). Of course, I had removed the little safety splint beforehand. Looks like I will need a new rear brake caliper since I don't see a chance to remove the broken screw without damaging the caliper.

But there is still the front wheel brake. I already tried to rinse away the crust with some water. This worked, but on applying gentle torque the screw does not move as well. I didn't dare to try harder yet since I don't want to snap the screw on the front brake as well.

Therefore my questions:

  1. Do I do something wrong or am I missing some detail about how to remove those screws?
  2. Is those screws getting stuck due to corrosion or something similar a known thing or bad maintenance by me?
  3. Are there any tricks to get the still intact screw going again without breaking it?
  4. As I will have to get at least one new caliper: How to prevent such corrosive problems in the first place? (Don't ride in the winter is not an option!)

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  • I'm guessing its a steel screw into an aluminium shoe ?
    – Criggie
    Commented May 14 at 22:32
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    Calvanic corrosion is the likely cause - when two "chemically different" metals come in contact in the presence of an electrolyte (e.g. salt water), they corrode and seize. Most commonly known from stuck seatposts. Usually happens when aluminum comes in contact with (stainless) steel.
    – Erlkoenig
    Commented May 15 at 5:17
  • Maybe the white stuff was actually threadlocker?
    – Michael
    Commented May 15 at 12:06
  • @Michael quite surely not. It looked like this white foamy crust that you have on sale exposed things after winter. Commented May 16 at 5:32
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    @BenediktBauer Oh that’s not too bad! Option A: remove the wheel and grab the backside of the pin (where the safety clip is) with strong pliers and try to remove that way. A drop of penetrating oil where the threads are and/or a bit of carefully applied heat would help. You may also be able to slide the brake pads to one side and grab the pin through the gap too. Option B: drill out the threads, and then either install a thread insert to restore the threads, or just use a cotter pin.
    – MaplePanda
    Commented May 20 at 20:53

1 Answer 1

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You can use the cotter pins from a pad like B05S to replace the screws completely. You may be able to drill out the snapped one and leave a hole that can take the pin.

If you suspect the other one might do the same, use needle nose vise grips on the accessible part of the shaft as you also turn the head. This way you're adding torque to maximize your chances of it working.

It tends to be corrosion that causes this. The best preventative is a mild threadlocker. You don't want grease or oil there.

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    Better than threadlocker is anti-seize, such as Park Tool ASC-1. It is designed to prevent this exact issue (calvanic corrosion). Also works for seatposts, bearings, freehub bodies.
    – Erlkoenig
    Commented May 15 at 5:09
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    @Erlkoenig Anti seize has a grease base and here it would be millimeters away from the pads. Too risky, a lot of people would flub it. Threadlocker will seal out moisture when it sets up and is safer to use around disc pads. Commented May 15 at 16:03

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