Model U Stop Ring

do u have to use the stop ring

Yes the stop rings are necessary. They control the wheels to make the pony go forward normally. If without them, or they are in the wrong position (see the link for more details:https://shopeu.ponycycle.com/pages/my-pony-is-all-well-before-but-suddenly-it-cannot-move-forward-when-kid-plays-it-what-happened ), the pony can't go forward.