Stiffness and handling work together to ensure the bike tracks predictably and responds immediately to critical pedal and bracing inputs.
Trail—front-wheel response to rider input—is the most critical factor in high-velocity handling. Flipping the two-position "Trail Mixer" to compensate for the difference in circumference between a 650b and 700c tire maintains consistent handling by maintaining consistent trail figures.
We designed Aspero to fit most 700c x 42mm or 650b x 49mm wheel/tire combinations. Of course, there are variables—rim width, tire casing, and tread depth—which will affect final clearance. We (and the International Organization for Standardization, or ISO), always recommend 4mm of clearance between the tire and frame.