Review on Adjustable MTB Bike Disc Brake Bracket Converter Frame Adapter Mounting Holder - Star-Art 20/31.8mm by Gregory Rasmussen

I gave it 3 stars because it probably does what it's supposed to do, but I just couldn't get it to work with my particular frame geometry. I read reviews about design limitations so I knew what I was getting myself into. I have a Trek Y50 that has a very unusual frame. The rear frame members that lead to the dropouts are rectangular in cross-section (joke), but I was hoping the metal on this adapter would be malleable enough to wrap around them. The metal "hinges" are a little pliable, but the problem turned out to be just the location of the dropouts. As you can see from the photos, the rear triangle has a much larger weld area than most "regular" bikes, so the adapter couldn't reach from the attachment point to the axle. It would be closer if I installed it on the bottom of the frame, but not close enough. This can be done with just one of the two screws as shown in the last photo. I added green tape to protect the aluminum frame while I tightened it. This is clearly suboptimal. Another option would be to cut the narrower loop to be closer to the axle. I'm looking at other possible solutions first as a bolt and hinge seems unlikely to me that they won't be very strong (and could also damage the frame). Worth a try for €9. As many other reviewers point out, be prepared for some mechanical work and the possibility that it just doesn't fit.