Is it possible? My commuter has twisty gear shifters (shim tourney from memory). My MTB has thumb shifters. I would really like thumb shifters on the commuter. Is this a simple DIY change? The reason for the change is that I have fitted bar ends to the handlebars for comfort; changing gear becomes problematic and I just generally prefer the set up of thumb shifts and the quicker gear change. Im a complete nood to bicycle tech stuff, so any advice would be appreciated; and if possible what I would need to complete the swap. Cheers in advance. Anil.