Dave’s winter/gravel bike

Dave’s winter/gravel bike

As a fellow Eugenean, Dave wanted a weather-proof bike for the winter. This means a belt drive with an 8spd Alfine hub, disc brakes and full coverage fenders. For all-road riding, we went with 35mm tires. The frame has an integrated seatmast, with a slight curve for tire/fender clearance. The seatmast also allows for a third bottle cage mount on the rear of the mast.

The goal was to keep the weight as low as possible, so the chainstay has a fixed length for the chosen gear ratio, with a custom split dropout for installing the belt. The Alfine shifting is handled by Di2 – to fit the Gates sprocket behind the motor unit requires an offset 28T cog. This sets the beltline quite far inboard, which results in some issues for chainstay/beltring clearance. To counter this the rear end is built offset to the right by 7mm. This, combined with additional shaping of the chainstays, allows for a straight beltline and clearance for the larger tires.

With the only rear sprocket option being 28T for the Di2 setup, to get the required gear range with the 8spd, a 70T beltring was needed. This is mounted on a FSA carbon crank.

The shifting is controlled by Dura-ace 9170 shifters, which connect to an XT Di2 display. As well as providing information on battery life and gear selection, this also allows programming of the shifting via Bluetooth with Shimano’s app. The hub can be shifted from either hand. All the wiring is internal with the battery in the seattube.

Enve’s 4.5AR rims have a 25mm internal width that pairs nicely with the 35mm Compass tires, which are setup tubeless. With the Alfine hub only being available with 32 or 36 spoke holes, to lace to the 24h rim a skip-hole pattern was used with the 36h hub, built asymmetrically to match the frame.  A White Industries CLD 24h front hub completes the wheel build.

The fork is Enve’s GRD model, which comes with the matching fender. But there is not currently a rear fender to pair with it. So two extra fronts were taken and modified to become a rear. Instead of a chainstay bridge, the fender mounts to a boss on the rear of the seattube, leaving better clearance and less impediment for wheel removal.

A nice thing about the Di2 system is that the same shifters can be used for the Alfine hub or a derailleur. Thus if Dave wanted to turn this into a gravel racebike in the future, it would only take the addition of a new rear wheel with a wide range cassette, a 1x chainring, and an XT or XTR Di2 rear derailleur. The dropout has the ability to add a derailleur hanger if this option is required.

Dave wanted to integrate the logo/colors for his company (Rogue Medical Solutions), so I asked Roger Riling to create a custom design. This was then applied by Colorworks. Total weight as shown (with fenders, no pedals) is 20.6lbs.

Rode the bike today and it was AWESOME!  So comfortable, handles like a champ.  Very happy  thank you.

3 Comments

  1. Rob, your bikes are amazing, you’re my favorite framebuilder to boot.

    Offsetting the rear triangle obviously works but as an unapologetic snob, I’m curious about solutions besides offsetting dropouts by 7 mm.

    Maybe a custom belt sprocket with corrected chainline would work?

    • Hi Jeff, many thanks for the kind words! The issue is using the belt drive. The Di2 motor fits close up to the dropout, and there is room behind it for a regular chain sprocket, but not for the 11mm of width that the Gates belt requires. To enable using the belt with the Di2 system, a special offset belt sprocket is used, which has to be 28T to be big enough to offset over the outside of the hub flange. So that makes things fit at the back, but the result is that the beltline is now quite far to the inside. It can just be made to work with a 25mm tire, but with a bigger tire there isn’t room for the tire/chainstay/beltring. Hence the offset rear wheel on this build. The other solution is to elevate the chainstay above the ring – this frees up space and also means that no break is needed in the frame for belt installation. I have taken this approach with a previous build: http://www.englishcycles.com/custombikes/andrzejs-fwb-special/
      thanks, Rob.

  2. Thanks Rob, that’s a dreamy bike! Love Geoff Mcfetridge too.

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