>>5957900This is the page that has instructions regarding the wheels/suspension.
It's a nip model, but on step 3 (which is the one about mounting wheels) there doesn't seem to be any extra instruction besides the visuals.
In step 2, part B14/B13 is the mount that has the ridge, whereas part B11/B12 is the mount without the ridge.
In step 3 it directs me to mount part C (which are the idler wheels assembled in step 1 from B18/B17) on all the idler mounts (B14/13 and B12/11 alike), so it's the same wheel. Without the ridge, the wheel doesn't attach because the spoke is too thick for the insert on the wheel.