[jd2013cambercomp]

I got the new rotor and the adapter just a little confused on which direction to mount the adapter. should the larger spacer be on the front or rear post. Thanks! If anyone could post a pic that would really help!

 

[cobba]

http://techdocs.shimano.com/media/t...0A/SI-8170A-001-ENG_v1_m56577569830667774.PDF

The arrow on the adapter always points in the direction that the wheel/rotor spins when you ride the bike.

 

[hatake]

Aside from reading that arrow correctly, the reason you put the cone/cup spacer is to allow bolts to sit straight into the brake mount post even with slight angle introduced by your 60-to-80 mm adapter which changes the angle of the brake caliper in relation to your fork/mount. If you, for example, use these spacers between the post and adapter or caliper, then your bolt would sit directly on angular contact surface of the caliper - that can potentially snap/crack the post by applying perpendicular force to the post.

So, it's very important to follow the direction in this particular instance.