My rack.
I had the same problem.
I ride a 61cm Specialized Sirrus.
The rack I bought (can't find the brand, but it came with a removeable child seat), came with 2 sets of stand-off brackets for bolting to the seat stays. Neither one worked.
So, I used one set for the seat stays, and one set for the chain stay. So, the rack is set up and back just a bit - but enough to get it out of the brake cable, keep it from riding on the tire, and keep my daughters feet out of mine when riding with the child seat.
I'll try and post a pic.