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Ceramic Bearings: Eight things to know
 
By Giles Belbin
Date: 11/6/2011
Ceramic Bearings: Eight things to know
 

Ceramic Bearings: Eight things to know
When thinking about upgrading a bike there are numerous things to consider, here's eight things to know about upgrading to ceramic bearings.

When thinking about upgrading a bike there are numerous options available, with frame, wheels and groupset just three possibilities that can really help performance. But for the rider seeking every possible advantage, an upgrade to ceramic bearings can bring tangible performance rewards. And in a sport where, thanks to Team Sky, "marginal gains" are now the watchword, for a serious racer they could just be the difference between a glorious win and a finish in the bunch.

So if you're a rider looking to make the very most of your ability, here's eight things you need to know about ceramic bearings.

1. Just what are ceramic bearings?
Traditionally bearings used in a multitude of applications, including bicycles, have been made of steel. Ceramic bearings first started to become utilised in high tech industries such as aerospace and performance cars and motorbikes. In recent years they have been used by professional cycling teams. As ceramic bearings have become more available and as costs have come down, they are now accessible to the serious amateur racer.

Bearings come as either sealed or unsealed. Unsealed ceramic bearings are single balls made of a ceramic material whilst sealed ceramic bearings can be divided into two categories - hybrid or fully ceramic bearings. Hybrid ceramic bearings retain steel rings, or races, but have ceramic balls. This contrasts with full ceramic bearings which have ceramic races as well as ceramic balls.

2. What are the differences between ceramic and steel bearings?
Ceramic bearings are mostly made using ceramic silicon nitride (Si3N4) which is both lighter and harder than traditional steel bearings, although zirconia is also sometimes used. The website Livestrong states that steel bearings have a hardness of around 30 million lbs per square inch. Ceramic bearings by comparision measure 47million lbs per square inch.

Thanks to silicon nitride being less dense than steel the bearings are up to a third lighter than comparable components made from steel. In addition due to the extra fine finish they are less prone to friction and therefore create less heat. They also require less lubrication.

3. What performance benefits do ceramic bearings offer?
One of the main obsessions of the serious cyclist is of course weight so any component that reduces the weight of the bicycle is naturally welcome. However, the performance benefits of ceramic bearings are not chiefly down to the weight savings they offer, but rather from their hardness and surface quality. These combine to create reduced levels of friction.

Neil Flock of Cycle Monkey, who offer ceramic bearing upgrades, explains: "Ceramic balls are smoother, so they roll with less friction. Most companies offering hybrid-ceramic bearings are using a harder steel alloy for the races (compared to all-steel bearings), which will polish into a smoother surface and compliment the hardness of the ceramic balls."

This reduced friction means that the bearings offer less resistance and so require less energy to roll. In a test report on bicycle.net, wheels fitted with ceramic bearings were spun and were said to have "just kept spinning and spinning".

Riders using ceramic bearings can also expect a smoother riding experience. Fitting ceramic bearings will make the bike feel like it is rolling smoother. If a cyclist has ridden a bike fitted with ceramic bearings and then returns to steel bearings, it is likely that slightly more vibration will become noticeable. Jonathan Day of Strada Wheels, says that whilst diffcult to quantify, a possible benefit to this reduced vibration could be less fatigue felt in the legs over the course of a long ride or race.

4. Is there any information available on the extent of the performance benefit?
Yes there is data available but it comes chiefly from the manufacturers themselves. According to the bicycle.net report, the manufacturer CeramicSpeed stated that ceramic bearings can offer power savings of between 10 -12 watts and bring heartbeats down by 2 - 5 beats per minute.

Other reports found by the dailypeloton claim that power savings at 25 mph equate to two watts and that on an 8% climb the reduced friction is equivalent to a stationary weight saving of 340g (zipp.com). BikeRadar.com meanwhile report a claimed advantage of between one to four watts, again at 25mph.

None of this might seem particularly significant, indeed Neil Flock from Cycle Monkey, says that ceramic bearings offer "marginal time benefits over the course of a race". But for a serious performance cyclist those slender, marginal gains can combine to result in a potentially significant advantage.

5. What are the cost of ownership benefits do ceramic bearings bring?
The relative hardness of ceramic bearings results in increased durability over comparable steel bearings. Ceramic material does not rust, unlike steel, meaning exposure to moisture is less of a concern, particularly for full ceramic bearings. They require less lubrication and do not suffer from pitting.

However, there is a risk of chipping, particularly where they are located in areas that are susceptible to water or grit ingress. So whilst ceramic bearings can last between 5 and 20 times longer than steel bearings it is important that they are fitted and maintained correctly. If so, Jonathan Day says that the increased wear resistance means that an initial investment in ceramic bearings should be paid back over time.

6. To what areas of the bike can ceramic bearings be fitted?
Ceramic bearings can be used to upgrade any steel bearing currently in situ on a bicycle. Primary areas are wheel hubs, bottom brackets and headsets, although jockey wheels containing ceramic bearings are also available.

Neil Flock from Cycle Monkey, says, "Putting ceramic bearings in hubs offers the rider the biggest perceived improvement due to the above mentioned change in rolling vibration, but the performance gains of this location are usually fairly small. Putting the bearings in an external bottom bracket is typically cited as offering the largest improvement in performance...I have read claims of up to a 4% increase in power by swapping out the BB bearings.

"Ceramic bearings are typically used in applications where high rotational speeds generate high heat, but this does not happen on a bicycle. However, rolling resistance is highest at lower speeds, so the reduced rolling friction of harder, smoother balls is what ceramic bearing companies are targeting. Therefore, using ceramic bearings in a highly loaded area like a bottom bracket will produce better results than using them in say derailleur pulleys or wheels."

7. How much can I expect to pay for ceramic bearings?
The price depends on the manufacturer, what type of bearing, its size and application and whether it is a hybrid or a full ceramic bearing.

For example Boca Bearings has ceramic ball bearings from $2.95 each. Hybrid sealed bearings range from $9.95 to $69.95, whilst full ceramic bearings start at $69.95.

8. Can I upgrade my bearings myself or do I need to call a professional?
Bearing upgrades can certainly be carried out by the user, especially if mechanically minded and already used to carrying out bike maintenance. Although in some cases specialist tools are required these are easily bought, often from the bearing manufacturers themselves. For example Boca Bearings has a range of tools here.

There are a number of on-line tutorials available to assist those that wish to carry out an upgrade themselves. Two of the best that the Daily Peloton found are at Wiki Books and at Active.com. There are also a number of video tutorials available including this one which demonstrates how to replace the bearings in a front wheel hub.

However, it is finally worth restating Jonathan Day's point that, in order to provide the best benefits in terms of durability, it is important that ceramic bearings are installed correctly.

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