sounds to me like whoever last worked on the brakes did not do a very good job. are all the bolts still there? have any broken or fallen out?

to do the st170 conversion you will need st170 hubs/knuckles, st170 discs and either st170 callipers and pads OR any mondeo mk3 callipers and pads.

easy bolt off, bolt on job for anyone competant with a spanner.