Shimano GRX Ltd show bike
Back in the spring, Shimano asked if I would do a build to be shown at Unbound to display their limited edition polished silver GRX group and new carbon wheels.
I took the opportunity to prototype some ideas, essentially testing a disc brake version of the Cane Creek bike, with some additional changes to the design and geometry.
There is a custom butted 1” seatmast, curved for tire clearance and with a custom internal wedge Thomson seatpost. A truss chainstay design – mirroring the fork and assisting in providing up to 50mm tire clearance with a double crank and short (416mm) chainstays. The oversize headtube has an internal sleeve between the bearings so the cables and hose can run internally, entering at the headtube, and have no interference with the steerer tube.
There are four bottle mounts and internally brazed bosses for a framebag. The front brake caliper attaches using direct mount bosses as more usual in the rear, positioned to suit the 160mm rotor.
The frameset has a powdercoat applied by Custom Powderworks, and the final weight is 19.5lbs. Many thanks to Shimano for the opportunity!
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English Cycles is Rob English, 
winner of Best in Show at the 2013 North American Handmade Bike Show. Custom bicycles built in Eugene, Oregon, USA since 2009.
Lovely bike! Do the truss fork and stays give added compliance over a more standard rigid fork? Also, how much height adjustment is possible with the seatmast? Thanks.
Mark
Thanks Mark. I don’t have any hard data yet to answer your questions – I am trying to subjectively observe but it is difficult when I have tweaked the geometry and have larger tires than my other bike. I can tell you that under a static deflection test, the rear triangle is not as laterally stiff as regular chainstays. But I can’t yet tell if this matters in a positive or negative effect when riding. The fork appears to be very stiff, which makes sense as it is triangulated. I want to do some static load tests with this too to get an objective answer.
The seatmast has about 15mm of adjustment; for client builds I generally increase this to 20mm and set it in the middle for +/-10mm.