Material can have a tremendous effect on ride characteristics, with steel, aluminium and carbon fibre among available choices.
Carbon fibre composites are intricate composites that rely on proper assembly to reach their full potential. Laying out fibre strands, resin and moulding techniques all play an integral part in how well a frame rides.
Stiffness
There is much myth, marketing hype and dubious engineering discourse surrounding frame materials; with each camp extolling their respective smooth ride characteristics. Steel or aluminium frames may boast smooth rides while titanium could have harshness issues or stiffness issues while carbon might provide stiffer yet stiffer ride characteristics than any of them combined. But in reality, your bike’s ride quality depends on both its design and materials used during manufacture.
Bicycle frames store and release enormous amounts of energy as you pedal, turn the wheels, and ride over road bumps. Some of this energy is released through frame flexing while some is dissipated via fork and suspension components.
Carbon can be engineered into an impressive combination of stiffness and light weight – an excellent combination for vehicle construction. However, rough roads may prove harsher on it than expected and damage and wear will eventually occur over time – it also tends to cost more than aluminium or steel options.
Lightweight
There’s often much marketing hype and unsubstantiated engineering speculation regarding frame materials, with various camps extolling steel’s smooth ride characteristics compared with aluminium’s harshness and carbon’s stiffness; yet the truth remains that ride quality depends on a good design regardless of material choice.
Aluminium makes an excellent material for bike frames as it’s both soft and lightweight while being quite tough – perfect for creating complex shapes that alter performance characteristics of frames. Welding can be done manually or machine, with welds being polished down for an aesthetically pleasing result (known as linishing). Aluminium welds may even be polished down (‘linished) for premium frames for added tidiness.
Carbon fiber plies can be very strong when tensioned but less so when compressed – leading to matrix cracking in epoxy-resin adhesive used to join them together and give compressive strength – but this weakness in compression could result in cracks appearing between plies if sufficiently hard impacts occur or manufacturing mistakes such as not eliminating all air from between plies.
Durability
There’s been much misguided conversation and marketing speak surrounding frame materials, with each camp championing (or denouncing) either steel, aluminium, or carbon as being better options to achieve a smooth ride experience or stiffer and rigid construction respectively. But in truth, all materials have their own advantages and disadvantages that must be taken into consideration before making your choice.
Steel has natural toughness that allows it to absorb energy without shattering into brittle pieces when stressed repetitively, known as fatigue resistance. Carbon, on the other hand, tends to damage more readily under repetitive stress than steel does.
Carbon used in bike frames is an unidirectional material akin to wineglass that only breaks along its length, and unlike metal it cannot be reamed or threaded for threaded bearings – therefore bearings must either be press fit into their bearing shells or added with metal inserts for full carbon frames. Bianchi use special resin called Countervail that filters out high frequency vibration and dampens it effectively.
Aesthetics
Steel has long been considered the go-to material for frame construction. It’s affordable and strong; its flexing helps absorb vibrations and bumps for a comfortable ride; however, steel’s heavyweight nature means protective coatings may be needed against corrosion. Furthermore, it can be challenging to weld – often necessitating tube-to-tube construction techniques instead.
Carbon is more flexible than aluminium but still stiffer than steel, and engineers can manipulate its flexing by layering fibre plies in different directions to control its bending. As a result, you often see carbon frames with thinner walls in the center and thicker ones near its ends to achieve maximum torsional strength while still ensuring longitudinal rigidity.
Titanium flexes similarly to aluminium, yet is much more costly due to labour intensive welding process and need for controlled environment for welding. Furthermore, titanium is known for being poor conductor of electricity and susceptible to galvanic corrosion with other metals – meaning custom and boutique bike builders tend to opt for this material more frequently.