Originally Posted by
cbrstar
I don't think it's a roller cam brake at all but likely a Shimano Deore XT U brake along the lines of a BR-M731 or similar model. You can't really use a V brake as it might hit the crank arm. They started putting U brakes on chain stays because chain stays have less flex then the posts on seat stays and the cable routing is simpler. But like everyone says on a MTB with mud etc getting stuck in it, and getting hung up on things was more trouble then the system was worth.
V brake and cantis won't work at all because the pivots (a) are in completely the wrong place (pads might contact the top of the tire but will be nowhere near the rim) and (b) the pivots are fatter and Cantis and Vs won't fit(IIRC).
Roller cams and U brakes use the same mounting posts and location relative the rim, but I think the whole RC assembly (including the 'actuation triangle') might not fit behind the BB shell.
The cable routing issue got figured out for the next generation of bikes ca. 1992 - run all the cables along the top tube.