Got myself in a sticky position with sons bike, my old one, could do with some advice.
Bought some new front forks for the bike as the old ones were beyond saving. So Rockshox Dart3 fitted with Post Mount for caliper. The existing brake is a Promax IS fit hydraulic caliper with a 160mm rotor. So bought a Brake Authority IS to Post Mount adaptor. Only trouble is it doesn’t fit. Apparently (CRC) its an IS to PM adapter not a PM to IS adapter, they say the only solution is to buy a Hope adaptor (HBSM20H)which it appears from the Hope site is right, but it means changing the rotor to a 180mm as well, which I could do without.
Also concerned as to whether it would fit. Sound advice most welcome!

Promax caliper is quite a bulky item, so a +0mm mount may not fit. HBSM20 mount should fit most brake/fork combo’s, and with a minor spot of filing i’ve got them fitted to forks they’re not supposed to fit(do this at your own risk).

Try this guy to see if he’s got any of the Hope HBSM20H mounts left (I bought the Hope C off him and was excellent deal)

http://www.singletrackworld.com/forum/topic/fs-hope-183mm-saw-rotors-pair-lots-of-disc-brake-adaptors

Thanks guys, I have sent him a message to see if he has any left.