Why do S Stock make such a loud squeal when braking?

It's quite common for trains to make a brake squeal noise, but S Stock specifically seem to stand out as having the worst/loudest.
Why is this and will it ever be solved? It's an awful noise.

OneTrackMinded said:

It's quite common for trains to make a brake squeal noise, but S Stock specifically seem to stand out as having the worst/loudest.
Why is this and will it ever be solved? It's an awful noise.

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Ironically they have composite brake blocks which generally produce less braking noise than traditional cast iron blocks!

Quite typical from Bombardier bogies from the period.

I’m assume it’s something to do with the design of the brakes and interestingly (although not sure if related) but when it comes to break squeal on trains it kind of feels like we’ve gone full circle in a sense. Old trains like 150s seemed to make a high pitched break squeal on as they came to a halt. Millennial stock like 170s seemed to be relatively squeal free, and then things like IETs and CAF stock squeal again!

Some brake shoe compositions simply squeal by nature. I have racing pads fitted in my car (for track days where they're expected to get very hot) and the same is true for them.