Reducing the three evils – draft, gravity and friction

Cheating speed evils: technological advances such as aerodynamic helmets and ceramic bearings are helping overcome drag, gravity and friction.

Cheating speed evils: technological advances such as aerodynamic helmets and ceramic bearings are helping overcome drag, gravity and friction. Photo: Eddie Barkla

The sporting world of swimming has just witnessed one of the greatest technological developments in swim suits that saw world records tumble at a rate like never before. When we stop and think it is the same body in the swim suit that powered through the water,  I guess this begs the question: “could the next big advancement in the increased speed in cycling come from the development of clothing that influences the affects of the aerodynamic drag?”

Cyclists spend most of their energy overcoming three major immutable factors: air resistance, gravity, and friction.

The use of aerodynamic helmets helps when down in the time trial position as the helmet lies on the neck and back of the competitor allowing the wind to flow over the rider. The use of aero time trial handlebars are now quite to norm for triathletes and road racing time trialers as well as skin suits that have minimal air drag over the body.

From another perspective design changes will always be in tension of keeping the balance for increased strength not compromising comfort on the bike.  Stronger harder components may not absorb the vibrations that can resonant through the wheels into the frame and forks.

From another perspective technological advancements for cycling will hold another tension of weight verses strength.  There has been many developments in getting fast wheel-sets that are light weight being strong enough to take the tensional pressure of the power produced and the body weight. Lighter frames and components advancements have reached a point where almost every bike brand has no problem making the UCI’s fairly arbitrary minimum weight limit of 6.9kg.

The one big factor that faces every cyclist is their own body which unfortunately comprise the vast majority of the gravity and aerodynamic drag but there is definitely a region of diminishing returns that can be made. We see this in riders that are good at certain disciplines – their body mass or lack of makes stronger fast muscles for sprinting or less muscle bulk that can sustain high intensity for longer periods such as hill climbing.

From keeping an eye on the developments it seems that there is a lot being made of the use of ceramic bearings. Ceramic bearings generally produce lower friction for a number of reasons. The balls themselves are much more round than even the highest quality steel bearings and are also much less compressible under load. In short, they start out rounder and they stay that way.

  • Thermal Expansion: Ceramic expands and contracts with changes in temperature 35% less than steel, so the various components of a traditional bearing can be made to tighter tolerance, offering cyclist less vibration and smoother motion.
  • Less Conductivity: Ceramics are electrically NON-conductive, and chemically inert, thus do not suffer from oxidation and the rust that degrades the surface of a traditional steel ball bearing.
  • Weight Reduction: Silicon nitride ceramic balls are only about 40% of the weight of bearing steel.

Less weight equals less rotating mass, making speed, acceleration and deceleration possible with less effort. Steel balls also have a nasty tendency to expand with heat that is generated during particularly heavy or high RPM loads. As they’re generally captured between an inner and outer race, this expansion can cause the bearing to bind.

Ceramics, on the other hand, have a much lower coefficient of thermal expansion. This makes them less likely to seize up in extreme conditions, but also allows them to be run with minimal lubricant. In fact, many ceramic bearings outside of the bicycle industry can be, and are often, run with lightweight oil or even bone dry. Ceramic is 50% harder than steel, so it takes a lot of work to alter its original shape.

We ran an article some months back on a wheel maker using ceramic bearings in almost all their wheels. So where else can ceramic bearing be used and reduce friction and drag?

The bottom bracket is a lot like the headset: it serves its role dutifully, tirelessly, and faithfully, with little praise or recognition. In fact, it generally doesn’t even come to mind unless something goes astray, in which case its very existence is cursed. However, even when they are working properly, it turns out that contemporary external-type bottom brackets typically produce a surprising amount of drag.

The large diameter bearing races have plenty of real estate for a greater number of ball bearings that are more capable of handling heavy loads, but all of those bearings and all of that viscous grease can also slow things down. Most external-type bottom bracket bearings are also of the full complement variety that omit bearing retainers, so all of those bearings are often in contact and rotating against each other in opposite directions. Moreover, those big bearings require big contact seals with lots of surface area. Naturally, more surface area contact equals more friction.

When it comes down to every little bit helps when athletes are so well match in strength technique and speed ceramic bearings maybe the reduction of friction that give that extra tenth of a second difference.

See you on the road soon God willing.


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