I am putting some Avid cable disc brakes on my wifes Trek hard tail. I used to have these brakes on my park bike, so they already had the adapter on it. Then I ran into a problem I have never had before. The rear adapter holes are at a different spacing. The frame holes are at 1.75" (44mm or 45mm?). My adapter is for 2" (51mm). I haven't found an adapter yet for this size. Can someone point me in the right direction?