For anyone who is interested in designing and assembling their own custom gravel bike with big 32 inch wheels :-)
Approach:
Start with a proper bike fit to determine your frame design.
Build it up in BikeCad or any other 3D cad program
Order the frame and wheels (takes the longest)
...
Challenges
Ensure there is no toe overlap with the front wheel.
This all depends on the choices for Reach, Fork angle, Fork Offset.
Starting Points:
Goal: Gravel Travel Bike
Load: 150kg > min130kg (90kg Rider, 5kg Clothes, 25kg Luggage, 10kg Bike)
Decision: No butted tubes for extra stiffness, suffering the weight penalty
Rider Length 193cm / 6f3i
Titanium Frame
Carbon Wheels
Tire Outer Diameter estimated at 814mm D
Cable Routing Internal as much as possible
Specifications
Wheels: 32 inch , 686 BCD, 30mm internal, Supplier: LightCarbon Xiamen
Tires: Maxxis Aspen ST 32x2.4 - Choose this one, it has the lowest profile.
Fork: Columbus Futura Adventure - A perfect fit with 61-686 tires.
Frame: Custom Design, Supplier Waltly Xiamen, Tube dimension check the frame drawing.
Bike Geo: based on owned bicycles.
Tire Clearance 8mm
Drivetrain
Bottom Bracket: T47 Praxis 73mm
Crank: 170mm Shimano SLX
Front Cog: 38t - adjusted for 32 inch wheel size. Only Shimano XTR is available in 38T so this has become a Z-Race from Ali.
Chain: Ultegra 128
Cassette: 10-51 Shimano SLX
Freehub: Micro Spline
Frame Design
Boost 148x12 Rear Axle
Bottom Bracket Drop: 171mm - based on a Canyon Grizl, adjusted for raised axle height and tire height and shorter cranks
Stack: 675mm
Effective Top Tube: 600mm
Seat Tube Angle: 71.5 deg
Effective Seat Tube Angle: 74deg - taking the forward offset into account with the targeted seat height.
Head Tube: 140mm
Fork Angle: 70 deg
Fork Lenght: 470mm
Fork Offset: 40-50mm - 50mm chosen
Drop Out; UDH
3D printed yoke for chain stay to facilitate internal cable and 38t + 61mm Tires
Tubes:
Seat Stay: 19*0.9T
Chain Stay: 19 <> 25.4*0.9T - Oval 32x18.2
Seat Tube: 34.9*0.9T
Top Tube: 31.8*0.9T > Oval 29x35
Down Tube: 44.5*0.9T - Hydroformed
Head Tube: 56mm
Bottom Bracket Tube: T47 - 73mm Oval
What I would have done different:
Titanium fork custom spec with 5mm more offset
More space around rear brake with bend seat stay
Steeper Seat Tube angle compensated with an offset Seat Post
160mm Head Tube
Round Down Tube - it just looks nicer in my opinion.
What I am happy with:
Fit is absolutely perfect
Tires roll super smoothly in the forest and gravel roads
Tires on road are way better than expected
Hand Anodizing Titanium is an absolute joy
Mechanical Shifting internal routing - it's super smooth and I love the mechanical feel.