I just switched my cassette from 11-23 to an 11-28 and I am having a really hard time trying to get my rear derailleur to shift correctly, it skips gears throughout and I can either not get it to shift all the way to the 28 or to the 11 depending on how it is adjusted. Would the length of my chain have anything to do with this? The chain is brand new, but when I got it put on I still had my 11-23 cassette on there, so it was lengthened for that, but I bought a new cassette a couple days later with the bigger gearing. I am not a very good mechanic, but I want to do this myself so I can get better. Any advice would be greatly appreciated.