Why Do Ceramics Have Less Friction?
Everyone knows that ceramic bearings have less friction than steel and thus perform far better, but few may understand why that is. And the answer to that is relatively simple, although multi-fold.
To start, ceramic balls do not corrode, nor do they cold weld — which is the process whereby forms of metals can wear through the adhesion of sliding surfaces (this process is also known as “galling”). In cold welding, or galling, the constant friction between the steel balls and the steel races results in a distinct gouging or scratching of the materials, which effectively transfers said materials from one surface and leaves it stuck to the other. What you end up with are uneven and rough surfaces that effect performance. This in itself is an advantage of ceramics, but because they don’t corrode or cold weld, they also don’t require viscous oil or grease for operation that would further effect their level of friction.
Ceramic balls are about 40% as dense as steel. This means less centrifugal force is developed on the bearings resulting in suppression of heat generation between the balls and outer ring. The result is superior high-speed performance and they can operate at higher speeds.Ceramic ball have a smoother finish than steel, A high quality steel ball bearing is consider grade 25. The grade number refers to the tolerance per millionth of an inch. A grade 25 is accurate to 25/1,000,000 of an inch. Less expensive ball bearings may be grade 300, which are less round, at 300/1,000,000 of an inch. Ceramic bearings may be grade 5 or 3 , which is a rounder ball bearing. so the vibration and spindle deflection is reduced allowing higher speeds and better performance
Spears Racing is currently inventorying the largest selections of Ceramic bearings for the the light weight bikes, Kawasaki EX250cc,EX300cc Yamaha R-3 and Suzuki SV650's.Check out the bearing applications inside of each of the "Products" listed for each Bike.
One of the advantages of ceramic balls is that they remove the problem of two identical materials
breaking each other down. This is measured as the coefficient of friction – which it is important
to minimize. Steel against steel has a friction coefficient of 0.8, whereas steel against ceramic has a coefficient of 0.2. This can be further reduced to 0.1 if the races are coated. This doesn’t mean that bearings with ceramic balls can run without lubrication over a longer period, but it does increase their tolerance to insufficient lubrication, which improves performance. The hardness and finish quality of the ceramic balls also serves to polish out any damage to the races, whereas this would lead to further breakdown and failure in steel bearings.
Compared to steel, ceramic materials offer superior corrosion and heat resistance, higher dimensional stability, and lower density, which facilitates high speed silicon nitride bearings have been used with successful results in machine tool spindles, special operating conditions including corrosive, vacuum , high-temperature, clean, non-lubricated.
First, ceramics are much lighter than their steel counterparts. As much as 50-75% lighter, the silicon nitride balls weight 60% less than equally-sized steel ball bearings, meaning there’s even less weight spinning inside the races. Secondly, and perhaps most impressively in our eyes, ceramics are incredibly strong. Another point in favor of ceramics is their resistant to heat. Steel balls tend to begin displaying integrity issues around 400 degree Celsius, while ceramics can easily operate at 2,000 degrees or more.
But the one attribute that ceramic bearings are most known for is their greatly reduced friction versus steel bearings made of any form of steel. How much better are they, you ask? about 1/10 of the overall friction. That means your wheels and other components can roll and roll all day.
All of this adds up to a form of bearing that not only performs better, but also lasts much, much longer. Some estimates in our research put it at five to ten times longer, although the actual useful life can depend on who you’re asking or what you’re doing with the bearings.
All of the Spears Racing Wheel bearings are hand packed with a High end Sodium Nitrite Inhibited Grease that is insoluble and has a decomposition Temperature of 320°C (608 °F)