The last is where most riders will notice the change first. The RC910 is built on SHIMANO DYNALAST 2.0, a reworked racing last with a wider forefoot and reduced toe spring. Toe spring is the upward curve at the front of the sole, and dialing it back takes tension out of the calves and hamstrings over long efforts while easing pressure across the ball of the foot. The optimized toe box gives the toes room to spread under pedaling load and reduces pressure across sensitive areas while keeping the midfoot and heel locked down. Narrow, standard, and wide fit options cover the width range rather than asking riders to solve width by changing length.

That three-way split has a practical consequence worth thinking about before you commit to a size. Riders who have historically sized up in Shimano purely to buy forefoot width may now be able to return to a shorter length that matches their actual foot, which usually improves both comfort and cleat position at the same time. If you have been riding a 45 to get a 44's width, try the 44 in the new Wide before assuming the old number carries over. The team at Excel can walk you through the three lasts side by side, which is faster than guessing from a size chart.

Closure comes from dual BOA Li2F dials running textile laces, which spread tension across the foot and allow micro-adjustment on the move without stopping. The Li2F dials release incrementally as well as fully, so you can back off pressure across the forefoot mid-ride rather than dumping the entire wrap and starting over. The upper is Japanese microfiber, chosen for low weight and breathability, and it wraps the foot seamlessly from toe to ankle so there are no internal stitch lines sitting against the skin under load.

Foothold at the rear comes from a reinforced carbon heel structure that resists the twisting load showing up when you stand and drive the shoe sideways through a sprint or a steep pitch. That structure is what keeps the heel from rotating out of the cup during maximum efforts, and it works with the stiff sole rather than against it. Taken together, the RC910 is a shoe for riders who already know they want a maximum-stiffness race platform and want the last few millimeters of stack taken out of the equation.