what does post mount look like in the rear?
I'm trying to update a older schwinn moab, part of which involves sticking some new hydros on. I'm not familiar with the rear brake mount though, i think it's post mount, but it's really just a flat spot on the chainstay with 2 holes drilled in to it. Does that sound like post mount? Are there different spacings of the holes that i need to worry about? Appreciate your help!
Yes. If the 2 holes are parallel to the rotor plane and 51mm apart, it is an IS standard. If it is parallel to the rotor plane but close together, then it is most likely a rack mount. If it is perpendicular to the rotor plane and 22mm apart, it is the old Hayes/Trek mount. Post mounts are 74mm apart.
2 holes on a flat spot on the chainstays is a 22mm mount. Thats an old Hayes mount, pretty common on late 90's to early 00's bikes. You can still get 22mm mount Hayes calipers from various parts supply places...otherwise I believe there are a few adapters out there to convert it to 51mm IS mounts