If you're staying with the triple crankset and just changing f/r der. you'd stay with the OEM (long cage) RD.MeSparks said:I'm planning to upgrade a Spec Roubaix triple to Ultegra derailleurs front/back.
Should I be using a long or short cage rear? Why would I select one versus the other?
Its more about the positive locking adjustment screws than performance.PJ352 said:If you're staying with the triple crankset and just changing f/r der. you'd stay with the OEM (long cage) RD.
FWIW, unless there's a reason to take the opportunity to upgrade, IMO it's not necessary, because you'll see no difference in performance with this change.
Short or long cage RD's are chosen based on total tooth capacity of the drivetrain.
Example: 5700-GS RD total capacity = 39T, 5700-SS RD = 33T
YMMV, but I've used both 105 and Ultegra and never noticed any difference in set up/ performance. There are a number of reasons why you're experiencing problems (assuming you are) that are unrelated to the quality of the components. They may simply need cleaning/ relubing/ readjusting.MeSparks said:Its more about the positive locking adjustment screws than performance.
There are 2 screws on each derailleur that limit its side to side motion. on the rear der. the inside limit screw prevents the der. from shifting the chain into the spokes, assuming it's adjusted correctly. The outside limit screw prevents the der. from shifting the chain too far past the smallest cog where it can get caught between the frame & the small cog.wim said:Now you got my curiosity up: what are "positive locking adjustment screws" on a bicycle derailleur?