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Out of curiosity, would anyone know what material Shimano uses for Brake Caliper Mounting bolts? Would Stainless Steel 316 be sufficient in strength if I needed longer bolts?

The particular bolt I am looking to replace is the standard Shimano M6 X 18.7 caliper mounting boltenter image description here

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  • Thanks for the reply, but I am unsure of the Shimano bolt material, and there doesn't appear to be marking on the grade used.
    – Larry
    Jan 19 at 21:28
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    Generic 12.9 metric bolt or a decent quality stainless will do. You only need 6-8Nm on these bolts, which is nothing crazy for a M6.
    – MaplePanda
    Jan 20 at 21:49

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Generally yes - fasteners on a bike are made from Stainless Steel, Steel, or High Tensile Steel.

There are occasionally fasteners made from Titanium or Aluminium for weight savings, but titanium is expensive and aluminium is weak.

Stainless Steel reduces rust/corrosion (but doesn't fully eliminate it) and is generally ideal for most places on your bike.

You'll also need to match the thread form, pitch, and diameter of the threadded part. The head also needs to suit the application and the length should provide sufficient engagement of threads without bottoming out in a blind hole.

For convenience, you probably want to have the same tool fitment as other bolts on your bike. That probably means a 3/4/5 mm hex tool or perhaps a T25 torx, or older bikes often use hex bolts in the 8/9/10mm range (or the imperial equivalents.)

Related - washers can also be stainless steel, should you need them.


Your other option is to check the existing bolts and figure out what they are.

Stainless steel is generally not magnetic, (or only very slightly)

Steel responds well to a magnet.

High Tensile bolts will have specific markings on the head to show what Grade of bolt they are - Example
https://www.boat-renovation.com/wp-content/uploads/2020/06/Bolts.png

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    If it's black passivated it's not going to be stainless. I would replace with (ordinary) stainless if I needed longer because that's easier to get than a decent passivation and you don't want them rusting if you can help it.
    – Chris H
    Jan 19 at 21:44

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