I hope this isn't the wrong section because I have a super newbie question about using a 'shift kit.' Question: (1) With the shift kit, does it mean that i no longer need to run a sprocket on the left side of the bike and can just rely on the right side cassette (gears)? (2) Or does it mean that I can shift from the left side sprocket that comes with kits, but also have the ability to use the bikes right side cassette? I wasn't able to get the WMV file video to play that is on SBP's site on my computer that probably explains this. Thanks.