Paul’s TT bike

Paul’s TT bike

Paul asked me to build him a TT bike for racing in the UK. He visited my fit studio in Oregon where we worked to get his position as dialed as possible. Without a TT bike currently, Paul wasn’t able to mimic the position on the road to test it out, so we aimed to allow for adjustment with the design so he could fine tune the fit once he had the bike. With this in mind, we went with the USE R1 aerobar, which offers adjustable stack and elbow pad position.

Bikes that I have built with a fully integrated front end have generally used a custom fork and stem so that I can cleanly integrate them with a narrow headtube and a smooth transition to the toptube. In this case we used the USE stem to match the bars (the combination allows for fully internal cable routing), and Paul requested the Oval Concepts Jetstream fork (no longer made, but I was able to find one as NOS). To make all this work I custom machined the headtube – it takes a regular 1-1/8″ external cup lower headset bearing, with a custom narrow radial top bearing. This allows the headtube to be the same width as the stem. There is then a fairing on the back of the headtube, which both joins to the toptube and contains the internal cable guide for the rear brake.

The toptube is shaped to mate up to the rear of the stem, and has a slot in the top that matches up to the cable exit at the rear of the stem. The cable housing stops inside the headtube fairing, with bare cable running through the downtube, over a custom guide on the BB shell to the chainstay mounted rear brake. Meanwhile I modified the front cable exit in the stem to allow for a bare cable run to the front brake.

The seattube is of airfoil section, sourced from the aircraft industry. It has an internal wedge bolt securing a custom small diameter seatpost to allow for simple saddle height adjustment. A wheel cutout tucks the rear wheel up close. I wanted to have some way to adjust the chainstay length to match different tire sizes so that they could all fit tightly to the cutout. But without losing the ease of use of having vertical dropouts. So I created an eccentric dropout system. This has aluminium inserts that effectively allow a regular road hub to act as a mini-thru axle system with an allen key skewer. This keeps everything clean and tidy, whilst giving 8mm of horizontal adjustment, which is plenty to cover any tires likely to be used on a TT bike.

Paul supplied the Dura-ace SRM crank, and specced an Osymmetric chainring, along with a 1x SRAM eTap setup. The chainring only comes in a derailing design, which combined with the short chainstays, means that a chainguide is needed to keep the chain retained. With no commercial chainkeepers able to cope with the large eccentricity of the chainring, I made a custom one. This mounts to a regular front derailleur boss (Paul requested this so that he can add a front derailleur later if he wishes).

Dash cycles made a custom two-tone saddle for the bike, and Colorworks matched the red for the logos and highlight colors on the frame. The final weight is 18.5lbs.

 

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