æz ðə "ɡˈɪɹ ɹˈeɪʃɪˌoʊ" ɪz ɐ fˈʌŋkʃən ʌvðə dˈɪstəns fɹʌmðə sˈɛntɚɹ ʌvðə dɹˈɪvən dˈɪsk, ˌɛni fˈaɪnaɪt θˈɪknəs ɔnðə dɹˈɪvən dˈɪsk mˈiːnz ðɪ ˈɪnɚ ænd ˈaʊɾɚɹ ˈɛdʒᵻz ɑːɹ bˌiːɪŋ dɹˈɪvən æt dˈɪfɹənt spˈiːdz.
As the "gear ratio" is a function of the distance from the center of the driven disk, any finite thickness on the driven disk means the inner and outer edges are being driven at different speeds.