CushCore 27.5" XC Tyre Insert SetCushCore 27. 5" XC Tyre Insert Set Light weight version designed for cross country racing, light trail riding, and or less aggressive riders. HOW IT WORKS Not all tyre inserts are created the same. CushCore is no ordinary tyre insert and is based on a new concept, tyre suspension. Any suspension system has a spring and a damper, and with CushCore, pressurised air in the tyre is the spring and the CushCore tyre insert is the damper. Like traditional