Friction and smoothness on the bike: go faster and get less tired
The friction and smoothness of the bike are two essential factors to take into account in order to go faster and tire less on the bike. However, raise your hand who really cares about that.
The first thing that comes to mind, to start improving performance, is to lose a few grams. Then we thought about aerodynamics. And finally, perhaps, we thought it might be useful to reduce friction to increase smoothness.Marginal gains is a concept dear to the hearts of many professionals: in a world of champions, every little bit of cunning can be the turning point.
1. Transmission friction
There are two types of friction:
- Those related to the size of the relations on which the chain runs.
- Those generated by a misaligned chain.
Studies have shown that the use of larger diameter sprockets and chainrings generates less friction. How can that be? Quite simply: the chain is less taut and each individual link works with a wider curve. Between sprockets 11 and 12, for example, there is an efficiency loss of approximately 1%.
This is why, especially in time trials, most professionals prefer an oversized crankset (up to 58 teeth) so that they can work with rear sprockets that are not too small.
However, this should not suggest that it is useful to cross the chain, to work with the larger chainring and nimble rear sprockets. This is where the friction generated by the misaligned chain comes into play.
Want some numbers?
In a 53-39 drivetrain, with an 11-speed 11-28 cassette, the tipping point would come at the eighth sprocket. In short, if we push 53×21 and we need a more agile ratio, it is better to change to 39×17 instead of using 53×23.
How many watts are gained? Few, you might say, but they are practically given away.
2. Cleaning and lubrication
A dirty chain runs less. This rule is old and very simple, but we often forget it.
There are more or less dense lubricants on the market, from different companies, and you can already perceive differences in smoothness between them. Not to mention the difference between a clean chain and a dirty one!
In addition, we can consider some special treatments for the chains, which make the gears even smoother.
3. Friction in the wheel bearings and bottom bracket bearings
Bearings and their smoothness play a key role in reducing wattage loss, especially bottom bracket and hub bearings.
What does bearing efficiency depend on?
3.1. Bearing quality
More expensive wheels and/or bottom brackets almost always use better quality bearings, which is not so much related to the material of the balls (ceramic or not), but to the precision and tolerances. A fairly inexpensive improvement is to replace the original bearings with high sliding bearings.
As far as the wheels are concerned, there is also a difference in efficiency between sealed bearing hubs and those with a cone and ball system. Although they require more maintenance, brands that use the cone and ball system do so because they find it smoother.
Like the chain, the bearings also become less effective if they are dirty. Once or twice a year they should be cleaned and lubricated.
3.3. Tips to improve efficiency
There are many professionals who use some tricks which, it must be said, sometimes shorten the life of the gears or, more often, require very frequent maintenance.
A very frequent intervention is the use of high flow liquid lubricants instead of the classic grease to lubricate the balls of the bearings. Sometimes the bearings are even degreased and left to run dry. Another common procedure is to remove the protective seals from the bearings. Here too there will be less friction, but the balls will be more exposed to dirt and the elements.
3.4. Resistencia a la rodadura
There are two rolling resistances:
- Externalfriction , i.e., the friction between the tyre and the asphalt: we now know that the solution is not a thinner tyre, but a slightly wider tyre that creates a shorter footprint on the asphalt.
- Internalfriction , i.e., the friction between the tyre and the tube, which is why tubeless tyres are softer.
Each point treated provides an increase in power, even if it is minimal. It is true that we are not professionals and, therefore, we often do not give it much importance… but there is one thing we would like to remember, and that is the essence of this article: there is no point in buying high-end groupsets or very expensive wheels if you forget to maintain them properly. A Ferrari with a clogged engine will underperform an SUV. For all cycling products there’s Deporvillage