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I have a full SRAM Rival groupset from 2011. Having used it in humid and rainy places for a while, most of the parts are OK, but the small button-head screws (or bolts?) in the QR pivot for the brake calipers are quite rusty. I guess the quality of these screws was somehow not up to the standard of the rest.

To be clear, I'm talking about a single screw per brake, whose head faces forward on the front brake, and backward on the rear brake.

Unfortunately, SRAM's maintenance guides do not call out these screws or dimension them in any way. How can they be replaced?

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    You can make a solution of oxalic acid (from a paint store) and soak the bolt in that, to remove rust. – Daniel R Hicks Jan 10 '15 at 3:14
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I can answer this question myself, having removed the screws, measured them, ordered replacements, got the wrong size, and so on. So other people can learn the easy way!

The screws (or bolts?) are M4x6 button-head. The threaded portion is actually slightly longer than the nominal 6mm on my set, closer to 7mm. But if you buy M4x8 screws you will find that they do not fit, because while the hole they thread into is plenty deep, it seems to be untapped beyond a certain depth. So 7mm is the absolute maximum threaded length for these screws, and you should buy M4x6. I chose titanium ones, but stainless would be fine too.

If you want to follow what I did, you should also see my follow-up question which describes how a tiny ball bearing will fly out of your brakes if you allow the QR mechanism to come apart when you remove the screw: What size is the tiny ball bearing used in SRAM brake caliper quick release detents?

  • I have numerous trips under my belt to a specialty hardware store in my area that has a vast selection of fasteners. However, most Home De'pot and Lowers also have a decentish selection. Usually if you take you old part in you can find something that will work. Keep in mind that if you find a replacement bolt that is too long, a dremel and file can work wonders. – Deleted User Jan 9 '15 at 17:34

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