Mechanical bearings help to reduce the friction between moving parts, proving to be a vital component in a wide variety of machines ranging from bicycles to airplanes. Bearings are a component that consists of five basic parts which include seals, balls, ball cages, races, as well as grease. Multiple balls are placed between races, which are concave surfaces. This allows the balls to rotate freely amongst one another with minimal friction (though one ball is typically fixed). The seals and ball cages help to hold everything in place, while also keeping out any dirt or debris. The grease helps to protect and lubricate the entire moving system. It is important to keep in mind though that not all bearings are created equally.
“The cheapest ball bearings may not even be perfectly round. Bearings are generally graded according to a scale of roundness, measured to millionths of an inch. A grade 200 steel ball means it is round to a tolerance of 200 millionths of an inch. Hence a lower number – grade 25 for example – is a much more precisely manufactured ball,”
said Stu Bowers from Cyclist.
“For the sizes used in bikes, grades vary from 2,000 to 3, with anything under 100 generally being considered a ‘precision ball’. This grading system is used for both steel and ceramic balls, as well as a further gradation for surface roughness, where ceramic usually achieves a much smoother outcome – just one of its inherent benefits.”
These minuscule differences in surface and roundness of a bearing truly do play a significant role in reducing friction.
“Ultimately, if the balls are poor quality and aren’t perfectly round or smooth, they will cause increased friction and premature wear and tear of all components of the bearing,”
said Alan Weather-ill from Hope Technology, a United Kingdom based component manufacturer.
“It will inevitably fail. The quality of the ball, regardless of the material, is the most important factor.”
“Here’s the deal: ceramic balls are generally rounder, smoother, harder and lighter than steel balls, so should theoretically provide less friction and greater longevity,” Bowers added. “They are also significantly more expensive, so it’s worth taking a proper look at the potential benefits of ceramic balls before parting with your cash”