Carbon soles and stiffness
Carbon soles and stiffness
The carbon sole has become de rigueur on high-end race shoes and increasingly on mid-range offerings, too. Equally accepted is the notion that a stiffer sole is a better sole, but is this always the case?
A shoe that flexes under load – easily replicated by holding the toe in one hand and the heel in the other and twisting – is of little benefit, but is a rock solid base that offers no ‘give’ counter-productive?
“Imagine you’ve got deep section carbon wheels, a carbon frame, and the stiffest crank on the market,” says Wall.
“Each time you hit a bump, it’s being transferred through the feet and into the rider, and that can fatigue the rider. Having compliance in the shoe can make a lot of difference.”
Many riders need a more compliant shoe than they imagine, he continues. An inflexible carbon sole that rubs against the ‘heads’ of the metatarsal bones can make the foot extremely sore.
He offers Lake as an example of a shoe that has a sole within a sole – a type of leaf-spring mechanism that offers some compression to absorb jarring from the road.
And not all carbon soles are of equal rigidity, he continues. Much like frames, some will have greater or lesser amounts of resin, and even a mix of materials in the composite, such as fibreglass.
For Hewitt, carbon offers a very supportive structure, but its benefit is contingent on comfort – all the support in the world will be of little advantage if the carbon rubs the foot with every pedal stroke.
Riders lucky enough to try a heat mouldable carbon sole that fits ‘from the box’ should leave it in its original state, he believes – moulding is only likely to succeed in opening the shoe to a degree where it may not provide enough support.