IIRC, the 987’s are designed the same as 986’s, but with a lower profile. I used the 986’s on my Rock Combo build.
The part that acts as the friction
stop against the frame has lands that are either 15 or 13mm (can’t recall - one of my cone wrenches fit it perfectly) so that the tension can be balanced between the two sides of the canti. Both sides can be adjusted so one can increase or decrease the spring load while keeping the tension balanced.
With the mounting bolt just loose enough, one increases or decreases spring tension then tightens the bolt. Repeat on the other side. It’s a great idea in principle: essentially infinite adjustability without the need for a spring hole in the frame. But it takes patience to achieve total harmony. Once you get the hang of it though, the process is pretty quick. They’re great brakes. Even better in purple!
