The schedule normally rotates where one team gets hit with a tougher schedule than the rest - here is just one example:
2016 was tougher for both WISCONSIN and IOWA
2016 - WISCONSIN crossovers @ MSU, @ MICH, OSU
2016 - NEBRASKA crossovers @ OSU, @ IND, MD
2016 - IOWA crossovers @ RUT, @ PSU...