Hi,
It actually depends of what we are talking about. If you take the example of callipers like Wilwood or Outlaw, yes, they have different widths according to a range of disc widths you can use the with.
Actually, these kind of callipers have all the same half-bodies, and spacers of different thickness’s define the disc width range you can use (see the sketch below).
2800draw_2.gif
Of course, the wider the callipers is, the thicker the bracket (carrier) will have to be for the same disc offset. The pad thickness has its importance too.
If we talk about original one-block cast callipers from a donor car, they might accept different disc thickness, but on a very small range to my mind.
Can you give more informations about what kind of callipers you bought, disc thickness (vented and non-vented) and bracket thickness ?
Thanks.