Help with movie title

[sanityremoved]

Hi, I was introduced to this site by a member of dvdtalk. Normally I would lurk and observe for a while but this question has bugged me for over 40 years.

I saw a movie on tv in the mid sixties on a B&W tv set. The scene I remember is of a couple riding a tandem bicycle. Something happens and then a werewolf has replaced one of the riders. Does anyone know what this movie is?

[Sebiale]

We'll probably need more details than that...
I recommend checking the site for all movies made in the sixties and before, see if any sound familiar.