Brake system replacement Currently I have a Tektro Auriga brake system. I don't like the Auriga brakes at all, so I decided to replace them with Deore XT BR-M800.

At front I have 180mm disk and between the caliper and fork is an adapter. I'm curious about the rear caliper. Will the new caliper fit without an adapter with a 160mm disk?
Here are pictures of my current brake system.(couldn't upload directly due to image sizes)
If the rear Auriga used no adapter for a 160mm rotor, the new M800 won't need one either.

Post mount frames can be understood to have a "native" rotor size, the size of rotor that a caliper works with when mounted without an adapter. For some bikes that size is 140, which would mean you would need an adapter, but it's mostly road bikes where you see that, not a hybrid or mountain bike that would be more likely to come with the brakes you have. Likewise some rougher stuff MTB bikes start out at 180 in the back and can't run a 160.