What's more, shifting the rear derailleur automatically trims the front derailleur. Priekinis pavarų perjungÄ—jas Shimano ULTEGRA Di2 FD-R8150 Brazed-on 2x12-speed. Designed to work with the wider gear pitch spacing Shimano chainsets without sacrificing shifting performance on bikes with 135 / 142 mm O.L.D.