Time Trial Mk2

Time Trial Mk2

The first bike I built with ‘English’ on the downtube was my time trial bike – built to allow me to get the position I wanted which I couldn’t do on a production machine. That was 2008, and I have raced five seasons on it – with three individual and three team state championships to show for it. Over the last two years I had been gradually planning the next iteration, taking what I have learnt and aiming to reduce the frontal area and increase the integration. I need to give some credit to Brandon Lee – I built him a very custom bike a while back, and discussions about a second project helped push my design work a step further.

Trying to integrate everything as cleanly as possible took a lot of long rides to think through and try and figure out, and even then there was some trial and error in the workshop too! I really wanted to eliminate any external fasteners to keep it all very clean. My position is not much changed from the previous bike, I just moved the aero extensions a little closer together. I also lowered the BB and decided to go with a single chainring, since I generally only race flat, straight time trials.

Shifters – Having had the opportunity to play with Shimano’s Di2 group on customer builds, I had learnt enough to hack the original 7970 group. With just a single chainring and only the rear derailleur to control, I rewired the harness and machined custom bar-end plugs to hold simple push button switches – up on one extension and down on the other. The control box fits into the stem and is covered by a cap. The wire then runs down the front of the fork/bar assembly, into the headtube and to the battery which is in the base of the seattube, inserted through a hole in the BB shell. Charging is via a micro-usb port located on the seatmast under the saddle. The wire to the derailleur then runs inside the seatstay. The wiring was somewhat tricky to install…. especially at 2am right before shipping the bike to NAHBS

Headset – Or perhaps just ‘steering bearings’ since there is no conventional steerer tube or headset. This was the biggest headache – how to attach two angular contact bearings and still allow for the brake and Di2 cables to pass directly through the headtube, with no external fasteners. The upper bearing is pressed into the ‘stem’, and secured with a small bolt. Before it was installed, an aluminium receiver was inserted into the inner race. This is slightly longer than the bearing so that it pulls down and locks into the headtube when it is bolted into place. It is also shaped on the top to act as an internal steering lock – this prevents the front of the fork/bar assembly from running into the headtube when the bars are turned. The lower bearing is pressed into the underside of the crown. For assembly, the bolt for the upper bearing is inserted through the lower bearing, passed up through most of the headtube and then locks the upper bearing and receiver in place. The lower bearing then has it’s own, larger bolt that threads directly into the inside of the headtube. This leaves the space between the two bolts open, so that the brake and Di2 cables can pass through. There is a machined slot in both the back of the fork/bar assembly and the front of the headtube to allow for these cable runs.

Brakes – I chose the USE Tula brake lever pods for their super aero profile and ease of access to inside the bar. For the rear brake there is a short 90 degree tube brazed inside the fork/bar which then connects to a short piece of ilink cable housing to travel from fork to frame. This two inch section of outer cable is the only piece on the bike. The cable then runs directly to an exit in front of the BB, over a brazed-on guide to the TriRig Omega brake. I really didn’t want to have to make custom brakes for this bike (it was a lot of work on the first machine), but I couldn’t find anything that would fit quite how I wanted it for the front. So I machined a small cantilever brake. The bare cable runs directly from the lever (which I had to modify to increase the cable pull), to a pulley on the left brake arm, then it is clamped on the right. A titanium spoke provides a central spring for both brake arms.

Crankset – Back in 2007 I built a prototype brazed cromoly crank, but hadn’t had time to return to the project until last year. The BB axle was actually the first part of this bike that I built. I have to give credit to John and Miles Kingsbury for the idea of using a tapered cut to align the two halves of the axle. The internal sleeve is a precision fit to keep the axle perfectly straight. There are two bearings on the drive side and one on the non-drive. The axle is 22mm, and the shell is a reduced diameter of 34mm. I considered doing a really super narrow crank, but decided I wanted to be able to run a regular spaced rear wheel, and so the chainring has to be located correctly. The cranks still have a q-factor reduced by about 20mm from normal though. The crankarms are airfoil shaped cromoly tubing, the same as used for the bars. For the chainring, Fibre-Lyte in the UK made me a custom carbon 55T ring, with three bolt spacing to match the cranks.

Frame – My original bike used round tubes that I ovalised. This one uses actual airfoil shaped cromoly. I could only find these in a thicker wall than I would normally use, and so I was reluctant to use tubes that heavy. But upon reflection, I realised that the thicker wall would add stiffness and allow me to use a narrower profile. The downtube is only 14.5mm wide, with an 18mm wide seatmast. Lateral stiffness is maintained by using an ovalised toptube, which being horizontal doesn’t increase the frontal area. My personal bikes generally have a fixed height saddle, and this is the same – I used a Thomson clamp assembly here. The rear dropouts are different – the drive-side uses a Breezer style to allow a clean exit for the Di2 wire, whilst the non-drive has a flat dropout, which is particularly clean when the minimal Tune skewer is used. The dropouts are vertical, which can be a problem with a tight seattube cutout. To allow for easy wheel removal, the dropouts are rotated back ten degrees so that the tire doesn’t jam on the brake during removal.

Components – There is not much else needed after all the custom parts! When I told Colorado-based Dash that I would be showing this bike at NAHBS, they stepped up with their brand new, 700g flat disc wheel, and a TT saddle to match. The front wheel is an Enve SES 8 rim laced to my custom extra narrow aero hub.

Total weight comes in under 17lbs. The paint scheme was designed by Jonathan Hill and executed to perfection by Eric Dungey at Colorworks. Thanks once again to Tina Buescher for the fantastic pictures.

I was honored to be awarded ‘Best in show’ for this build at NAHBS 2013 in Denver. If my legs co-operate, then hopefully it will go fast in races this year too!

 

 

 

 

 

7 Comments

  1. It’s great bike!

    Thanks for the props! :-p

  2. Bonjour
    je suis paationné par les vélo de cours acier, j’ adore votre travail, vos vélo sont magnifiques !
    j’ espère un jour vous passer commande, le model trial MK2 est idéal pour moi, je le trouvé tellement racé.
    merci d’ exister

    yannick
    France

  3. awesome bike ! WOW !

    would like to order a fixie / pursuit configuration someday !

    cheers !

  4. Beautiful bike! I want one!

  5. I want to use this design to build my track bike(or fix with brake). I really like how you made the fork(reminds me of look l96 fork). I really want to know how you made that fork with steel. Now I have to save money for your bike. lol

  6. I keep going back to this bike. Is there a reason we don’t see you on it more often?

    • Hi Caleb – I raced the bike the first season after I built it. But since then I have had some major issues with the Di2 and some minor issues with the front brake. And haven’t had the time to fully resolve them! Hoping to get all that sorted this winter so I can race it again next year.
      Thanks, Rob.

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