There's a small piece of metal in my (Ultegra) brake pad. More than one, actually. It seems to have scratched the rim. Presumably this is a manufacturing flaw?
The metal is from your rims. I found the Shimano R55C3/4 pads picked up a lot of metal from my rims, causing scratching and horrible noise when braking.
I was always having to take the wheels out and dig the flakes out.
I switched to Swisstop pads and never had this issue.
There's a small piece of metal in my (Ultegra) brake pad. More than one, actually. It seems to have scratched the rim. Presumably this is a manufacturing flaw?
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