Bikes of the Bunch: Mosaic RS-1

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In this edition of Bikes of the Bunch, Mark Hinsley shares the story behind his new steel bike, a custom-built Mosaic.

I have been riding carbon bikes for 10+ years and really wanted a change and something I could bespoke. I was looking at a variety of options including Speedvagen, Festka and Field. I ended up landing on Mosaic, a company with a reputation for building quality steel and titanium frames in Boulder, Colorado.

The RS-1 is Mosaic’s top-end steel offering, and that was the bike that caught my eye. I engaged with Steve at Crankstar in Brisbane to order the frameset and Zak at Skunkworks in Bondi to build the bike. Both were exceptional to work with and I would highly recommend them.

The process was a relatively smooth and quick, requiring about three months from first email to the frame landing in Bondi. I got my measurements done at Body Mechanic in Sydney prior to getting the drawings done up and pulling the trigger. The final decision was the paint job — I wanted something fresh and timeless. The denim blue and white polished finish is just what I was after.

I opted for reliable Shimano Di2 running gear with an InfoCrank powermeter and eebrakes. Zak recommended the cranks on the basis of their reliability while I liked the eebrakes for their industrial aesthetic.


Frame: Custom Mosaic RT-1 using True Temper S3 tubing
Fork: Enve 2.0, tapered steerer
Headset: Chris King i7
Stem: Zipp alloy, 120mm
Bars: Zipp SC80 alloy
Bar tape: Busyman Bicycles
Shifters: Shimano Dura-Ace Di2
Derailleurs: Shimano Dura-Ace Di2
Brake callipers: eecycleworks
Cranks: Verve Infocrank, Praxis chainrings (52/36T)
Pedals: Shimano Dura-Ace
Seatclamp: Thomson
Seatpost: Zipp alloy
Saddle: Specialized Romin Evo, refinished by Busyman Bicycles
Wheels: (i) Chris King hubs with Curve 38mm carbon clincher rims and Vittoria Rubino Pro Speed Graphene tyres; (ii) Chris King hubs with HED Belgium C2 Plus rims with Vittoria Corsa Graphene tyres.
Bidon cages: King titanium
Extras: Skunkworks hidden Di2 junction box, Fetha custom Garmin mount, D-fly Garmin integration, Skunkworks black Ti bolts, Busyman Bicycles custom saddle bag.

Zak built me two wheelsets for the new bike — one carbon (Curve) and the other alloy (Belgium) — with Chris King R45 hubs with ceramic bearings. I use the Curve wheelset on the road and swap to the Belgium wheelset for gravel bashing.

Zak has been doing a lot of work with hiding Di2 junction boxes. He was able to drill some small holes in the alloy bars so that he could hide the box in the stem. He suggested adding the D-fly unit there too so I can use my Garmin to not only track my gear changes but also to keep an eye on the battery charge level.

I finished the build off with amazing work from Mick at Busyman Bicycles. He came up with a perforated pattern over a blue to white fade for the saddle and then created matching bar tape as well as a saddle-bag for the perfect touch.

I wouldn’t change a thing about the new bike, it is truly my dream machine. It’s very comfortable yet offers a responsive ride, which I think is impressive for a bike with a 59cm top tube. I’m also surprised at the lightness of this bike — the RS-1 really isn’t much heavier than my BMC teammachine.

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