problemwith painting brake calipers is getting a good key.
they tend to be coverd in sh!t and rusty and people only clean them in a half arsed manner so paint only sticks in a half arsed manner. hammerite is good at clinging onto not much. VHT paint tolerate heat well but demand excelent surface prep or they just fal l off
if you shot blasted them pritty much any paint would stick and stay.