Archive for April, 2011

The Front Derailleur (Un)Standard

Thursday, April 28th, 2011

Sram X9 Derailleur mounted to a Niner Sir9 Front derailleurs can be one of the most confusing parts of a bicycle, this is in part because they come in a vast variety options. Hopefully this article will take some of the myth out of the front derailleur and help you on your next repair or bike build.

Cable Pull

Side by side look at top vs bottom cable routing Cable pull is the orientation of the cable as it interacts with the derailleur and is determined by the routing on the frame. Road bikes/frames traditionally use a bottom pull system, therefore the road derailleurs typically will be bottom pull as well. A large percentage of cyclocross frame use top pull routing despite the need for a road derailleur to match most drivetrains. This may seem counter productive but serves a valuable purpose in that it keeps the cable and guides away from a lot of the mud, grime, and debris a bottom pull system would see. To make everything mesh, most cross frames will incorporate a guide wheel to redirect cable appropriately. Mountain front derailleurs come in bottom, top, or dual pull (derailleur will work on top and bottom pull frames) options as mountain bikes vary largely in how the frames are designed.