I have an “older” Cervelo One (pre-Dual) equipped top to bottom with stock 105 components. I am going to change the chain and cassette on it. Is a 105 front/rear derailleur compatible with an Ultegra cassette and/or Shimano HG93 chain (which is on sale at Nashbar right now)? Thanks for any help.
Yup, you’ll be good as far as I know. There are several series of Shimano chains and cassettes: “HG” for hyperglide and “UG” for Uniglide. You are well advised to not mix them inadvertently. AS long as your cogset is “HG compatible” and your chain is “HG” you are good to go.