Why not ask the manufacturers, why?
And the Gevenalle Brifters , put thumb shifters on the front of a drop bar brake lever..
combining 2 simple , reliable , mechanisms..
Have used sun tour * bar end shifters for 40 years
* My C&V Campag , uses their friction bar end shifters ...
....
Last edited by fietsbob; 03-13-19 at 10:26 AM.