Frame stiffness, both in terms of lateral stiffness and vertical compliance, is an incredibly important consideration when it comes to engineering a bike frame. It is the special sauce that defines how well a bike rides.
So much so that when brands are designing their latest flagship race bikes, it's given the same importance as aerodynamics and weight. Some will chase new stiffness targets, but others will have these figures set in stone as immovable targets from the beginning, as they aim to retain the DNA of the platform while improving its performance elsewhere.
