Originally Posted by
alarsen77
Hi guys I have a Cannondale CAAD Optimo Disc 105 that came stock with a 50/34 crank and an 11-28 cassette. I am almost positive the rear derailleur is a short cage 105 rear derailleur. This is my first road bike so I have been struggling up hills and I am on the heavier side so I know I have a while to go before I am in the best shape to tackle hills. So I am considering going to either an 11-32 or even the new 11-34 that shimano has in the new 7000 series 105 cassettes. I know I will have to upgrade the rear derailleur to a gs series. Is there any reason to not get the new 7000 series rear derailleur since I am going to have to get a new rear derailleur anyway? Are there any compatibility issues with newer components and older components? Sorry if these sound like obvious questions but I am still learning a lot about cycling.
Also would it be worth it to at this time upgrade the rear cassette and derailleur to the Ultegra R8000 series at this point and keep the 105 STI levers and Front Derailleur? I noticed there isn't much of a cost difference between the R7000 and R8000 series components.
I would start with the 11-34 and a new chain. You may be able to use the RD still. I use a short cage RD with a 11-32 on multiple bikes. What is usually means is you can't use the 34x11 and 34x12 combos but they aren't necessary anyways. Size the new chain using big+Big+2. Crank in the b-screw and see if it will shift.