I have a Diamondback Haanjo that came with a Shimano 5800 105 drivetrain. This bike has plenty of room for wider front tires but I couldn't fit anything wider than a 40mm on the back wheel, due to the lever arm of the 5800 front derailleur (it almost touches the sidewall when it is on the big ring). I installed a Chorus front derailleur and it works beautifully. It shifts fine, it is much easier to adjust than the Shimano, and it looks like I can now fit at least a 45mm tire on the back.
