For example, see "Some recent developments in bicycle dynamics" (2007). Especially the folklore section:
"The world of bicycle dynamics is filled with folklore. For instance, some publications persist in the necessity of positive trail or gyroscopic effect of the wheels for the existence of a forward speed range with uncontrolled stable operation. Here we will show, by means of a counter example,that this is not necessarily the case.
https://pdfs.semanticscholar.org/bb70/d679c5a2ff67dd2a1a51f2...