Originally Posted by
scyclops
Assuming the disc rotor is 6"/160mm, the caliper should bolt on to the Dart fork without an adapter (as dminor said).
This is assuming that the brake is a post mount type.
I found a photo of a similar model Apollo bike with a IS mount mechanical disc brake.
Apollo.JPG
However, it occurs to me that some cheaper disc calipers (Promax, for instance) don't use an adapter and won't work with the post mount - but someone will correct me if I'm wrong - again.
Promax brakes can and are used with adapters, I think that the most if not all of the current Promax brakes are PM and they can be directly mounted on a PM fork or mounted on a IS fork with the appropriate adapter.
Some of the older Promax brakes were IS mount and there might of been some limitations to mounting these to a PM fork as there is with other brands of IS mount brakes. There is adapters for mounting IS brakes on PM forks but not all brakes can be used with the 160mm adapter/160mm rotor, sometimes the only way the brake can be used is with a 180/185mm adapter and a 180/185mm rotor.