Can’t remember where I first read about these, but it worked for me. If I recall correctly, they make one for discs and one for drums. That’s about as much research I put into it before trying it.
So these valves keep a small amount of pressure in whatever circuit you add them to, to offset the pressure drop from addition of the larger (than system was designed to run) calipers? Interesting. How does one ascertain what residual pressure is OK, without causing a pad drag issue?
(Link doesn't work for me, Safari keeps asking for multiple client ID certificates when trying to load it)