I have just bought a bicycle/road bike. It is a GT zr 5.0. It has sora components but the old owner upgraded to Ultegra brakes and Shifters. My question is what is the components do I need to make the changes to all Ultrega. According to reviews of this bike by members of this group...they say the sora components are garbage and they should be upgraded to ultrega. If you go to the reviews of this website you will see what I am talking about. I know I need to change the front and rear derailleurs, but does anybody know the part numbers, etc. Also is there anything I need to change. It is 8 gears rear now...I can change the cassette too, but I don't know what parts to buy to make the changes...anybody that can help me would be appreciated.