John’s TT/Pursuit frameset

John asked me to build him a frameset that could be used as a fixed gear time trial bike (with the addition of a front brake), and as a pursuit bike for the track. The design goals were to match his positioning and make everything as aero as possible. John requested a custom stem with a removable faceplate so that he could easily swap bars between road and track. That way the brake can remain cabled up for the road setup, and his aerobars can be a little lower for the track. He already had the USE R1 basebar, but wasn’t happy with the stiffness or angle of the standard extension mounts. So I built custom risers/extension mounts, which put the pads in the right position and at an angle of twenty degrees. I also built a second riser unit with less rise to be used with another basebar for the track setup.

The integrated seatmast is made from a custom rolled airfoil section 4130 tube, with a mini-seatpost secured by a set-screw activated internal wedge. A wheel cutout matches the shape of the rear wheel. The toptube is ovalised and flows into the stem, whilst the downtube is a teardrop profile from Columbus.

A set of FSA headset cups were modified to sit fully inside the custom machined headtube, so that the fork (Columbus Tusk Air) would match up precisely. The stem has the topcap built in for preload, and is secured to the fork with three M4 pinch bolts. A section of aero tubing behind the headtube cleans up the airflow there and reinforces the toptube junction.

Dropouts are from Bentley Components, with brazed-on stainless faces for durability. John also wanted to protect the paint on the fork with the brake being taken on and off, so a stainless washer was bonded to the crown, and then masked off and polished. Paint is by Colorworks.

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