FYI, in any roller coaster application, Nylon, or high speed wheels allow the vehicle to travel faster, while poly wheels generally slow the ride vehicle down. Joker opened on 100% Nylon wheels to assist with break in procedures. However, very similar to Medusa, Joker now runs a mix of Poly and Nylon wheels to "tune" and adjust the overall target cycle time. Hope that helps.
Still tuning,
Charles