02
Geometry
House road
geometry
Five sizes we can build from stock mitres, and the starting point for every custom drawing. Everything below is measured to the frame's centrelines with a 42 mm tyre and a 45 mm fork rake.
02.1
Drawing
Size 56, side elevation
02.2
Table
Five sizes
| Size | Stack | Reach | Top tube | Head angle | Seat angle | Chainstay | Trail |
|---|---|---|---|---|---|---|---|
| 50 | 518 | 368 | 525 | 71.5° | 74.5° | 425 | 63 |
| 53 | 545 | 378 | 545 | 72.0° | 73.5° | 425 | 60 |
| 56 | 570 | 388 | 565 | 72.5° | 73.0° | 425 | 58 |
| 59 | 598 | 396 | 585 | 73.0° | 73.0° | 430 | 56 |
| 62 | 624 | 404 | 602 | 73.0° | 72.5° | 435 | 56 |
02.3
Notes
Why these numbers
Trail before everything
We hold trail between 56 and 63 mm across the range rather than holding the head angle. A slack head angle with a long rake and a steep one with a short rake steer similarly; a frame that keeps trail constant across sizes feels like the same bicycle to a short rider and a tall one.
Chainstays at 425
Short enough to be lively with a 38 mm tyre and a 34-tooth inner ring, long enough that a size 62 does not put the rider's weight behind the rear axle. Above 59 we lengthen them, because otherwise the big frames wag.
Seat angle follows the rider
The table slackens as sizes grow because femurs do. In a custom build this is the first number the fit session moves, and it moves the top tube with it.
What we will not build
Anything with a trail figure under 45 mm, a front-centre that puts a size 12 shoe through the front wheel, or a down tube sized for a rider 30 kg lighter than the one who will ride it. We will explain, and we will draw the alternative.