The shimano dura ace r9170 features a 40 mm deep carbon disc rim the depth of the rim adds aerodynamic properties to the wheelset making riders faster over the line whilst the alloy braking track allows assured braking in all conditions the c40 combines this with a 24 mm rim width allowing riders to choose wider tyres using a wider tyre 28c creates a greater contact patch with the ground and allows for a more linear bond between tyre and rim giving the rider greater cornering ability an