There definitely appears to have been an experiment with longer wheel base for that year. If you look at the 53cm the year previous, '89, the TT is 52.5, the year following, '91, it's 54.5. The respective wheelbases in millimeters for the '89, '90 and '91 model years (though I have more trouble seeing these) are: 957, 1018, and 979.