Originally Posted by
karlamei
...it seems like I don't need the disc break offsets?
My local REI where I bought the rack had a Topstone in stock, and we were able to place the rack on the back as a mock-up, because I had this exact concern. Turns out the disc brake model is unnecessary on the Topstone, and I went with the standard MTX rack. Still has the thru-axle issue though.
I think the disc brake MTX rack is for when brake housings aren't flat mount, or aren't limited to the inside of the rear triangle. The REI employees were astounded that it looked like the standard rack fit.
If it truly doesn't work for you, hopefully you can exchange it.