Source cervelo.com:
We engineered Áspero for pure, unapologetic speed, ready to take down finish lines, KOMs, PRs, and FKTs. A bike built without limits, for the riders looking to test them. It’s stiff—Classics-racing stiff—and performs like you’d want a road bike to perform off-road. We think that makes sense, and it’s what we were trying to do when we were stuffing bigger tires into our existing frames and swapping in aftermarket forks to get a 40mm tire up front.
TWO-POSITION ADJUSTMENT
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.
MULTIPLE CONFIGURATIONS
We designed Aspero with clearance for up to 700c x 40mm tires or 650b x 49mm tires. 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.
**New Shimano road (not gravel) 12 speed front derailleurs reduce tire clearance in the rear of the frame to 700 x 38c or 650b x 45c..
BALANCED HANDLING
Stiffness and handling work together to ensure the bike tracks predictably and responds immediately to critical pedal and bracing inputs.