I bought something like this (but not this one, this is just a stock image. On mine the legs with the bolt eyes are assymetric) off the classifieds recently, marked as 'front, 160mm'.
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It seems to sit too far out from the rotor, such that only about half the pads are overlapping the edge of the rotor. Could it possibly be a rear caliper on a short hose and RH lever? Can't think of any other explanation.
Cheers
The callipers are interchangeable yes. They go down by 20mm when moved to the back so unlikely to be what your describing. Its possible it could be a 180mm (the calliper position moves more than just out I think). Hope IS callipers have a number on them normally (e.g. 3 or 5), this will tell you the size (with a bit of goggling).
This is mine:
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It has '3' stamped into it. I guess a 20mm larger rotor is only 10mm greater radius, so about half a pads worth. Hmpff.
Cheers
The no. 3 caliper is a 180mm front, 160mm rear caliper.
Yes and you'll require a No.5 if you want to use a 160mm rotor up front