Felt pushed its ultra-high modulus and Textreme composite technology to the F4X machine. Subsequently, the F4X wins the award for stiffest overall frame in my cyclocross grouptest this year, but for some this might take a toll after 30 or 40 minutes of full-on effort.
While the stiffness can be a true benefit when pushing the limits, it can also impede traction when accelerating or braking if the conditions are rough. I suspect this is something riders would learn to adapt, but it could lead to compromised line selection, which is critical in ‘cross racing.
However, when the wheel stays in contact with the ground that stiffness is a blessing in many circumstances, so depending on your typical course terrain, the F4X could be good for you, or not.
Depending on your preferred tires and your regular racing conditions, the bike could offer a limitation for mud clearance. A 37.4mm wide (measured) tire is barely fitting with 3mm of clearance, so wide, treaded mixed-terrain tires are a no-go.
Future versions would benefit from growing the rear chainstay and seat tube junction for more tire clearance. Dropping the seat binder lower could also add compliance to the rear.
For riders seeking absolute stiffness, the F4X delivers.