Ben’s aero road disc

For Ben’s first bike we went for multi-purpose, with a 700C wheelset and a 650B set with larger volume tires. A few years on, and Ben realised he was riding the bike in 650B mode most of the time, so asked me to build him a dedicated fast road bike around the 700C Enve 4.5AR wheels.

Ben experimented with his position to see if he could comfortably get a bit lower to be more aero – once we had the handlebar position set I started work on the frame layout. Ben is tall so the headtube is quite long. We considered using Enve’s internally routed stem/headset/fork system, but this requires an oversize headtube and I wanted to keep the front end as slim and streamlined as possible. With some experimentation I created an aero-shaped headtube from a section of Columbus airfoil downtube, with the ends carefully shaped to accept brazed-in rings for the headset cups. In creating this headtube, I realised the shape left room behind the steerer tube where the rear brake hose could be routed. So I added an internal channel for this, and an entry port behind the upper headset cup. Then I found that the Allied fork was open from the blades to the steerer, so the front hose could run up the inside of the fork to the top. This way the hoses are only exposed alongside the stem, whilst keeping a very narrow, clean front end.

To allow for the fully internal rear brake hose, there is a T47 BB. The custom butted and shaped aero seatmast is offset slightly to the rear of the BB shell to allow room for the wheel cut-out without compromising the chainstay length. For long rides there is a third bottle cage tucked behind the mast.

The build is completed with an Enve cockpit and a SRAM Red AXS eTap groupset, the paint is by Colorworks, and the final weight came in at 18.9lbs.

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