The substance taking the city potholes and turning them on their heads the substance breaks over these crags amp bumps in much the way a 29er would in its army green and blue finish itrsquos got a look that gets better with a little bit of dirt and grime but there is much more to the substance than just an about town commuter shimano tiagra drivetrain the shimano tiagra groupset gets a revamp for 2016 in looks design and technology following on from its older brothers it offers