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Existentialism-- Just a bloody good excuse to go riding...

Sunday, September 18, 2011

Ceramic Bearings

Bearings. Ceramic vs steel, its one of those epic never ending argument which is better or is ceramic really worth the moolah one doles out. I personally find that there is too much marketing hype surrounding ceramics. Sure, from all the testing and data, it all points to ceramic being more superior. But what is that relevance in the context of your average rider or in fact for cycling in the first place? The only thing I could think of that benefits me is that the balls wont rust like steel ones should maintenance and repacking of grease is neglected. As to smoothness and the spinning, that to me is just one big myth. Whatever minute friction co-efficient that is lower in ceramic is mostly knocked off after grease is packed and seals are snapped shut on the bearing. Those 2 accounts for most of the "unsmooth" action of a bottom bracket that riders feel.

Having said, all of these is pretty much theorized from my bias of just extensive reading and experience with steel bearings. Too cheap to fork out for a ceramic, I had to wait till someone throws out one for meto take a better look and salvage if possible.

Gotta love Facebook...u just get to know people from all over and get to put my greasyt paws on their "throw-away" items. Of course central to this whole article was an Aerozine Ceramic BB using 6805 2RS bearings.

Like its steel counterpart, if any side were to go wrong I would put a bet its the non drive side. Sure enuf after cleaning up the outside and with outer seals pried, its surface rust on the external of the left cup. No biggie, this alone shouldn't cause a problem unless the insides are rusted too.

Open up and the problem?? .... the original stock grease. Now I have known from stripping bearings over the years, packing enough grease in bearing is something of a hit and miss. A lot of manufacturers don't put enough. This probably has something to do with the smoothness but more on that later. The problem is if the bearings with lesser greease arent being maintained often, the balls will wear out fast and gets pitted. The case here is not that there is insufficient grease. On the contrary there is quite a lot but looks pretty dried up. Not too sure if ceramic ball specific grease are meant to be like this. If it is then another myth of ceramic bearings being smoother are busted. The more viscous a lube/grease, the less free spinning the balls will be, hence it means more effort needed to keep things turning.

So the logic is to degrease, use a light oil and if possible remove the rubber seal to minimize friction and or simply to increase thefree movement of the whole bearings? Yes it works but it is a trade-off with having more frequent maintenance. If a bearing is tweaked to such a state and happen to get into water, then there is no protection and likely to be junked in a short time if not cleaned up in time. The other con to it is the noise... when it is not packed, the sound coming off from the balls contacting the race is noticeably louder and rougher. This is often mistaken by folks that there is something wrong with their bearings" Nope its not. A seized bearing or one where it is work down until you can feel some lateral play when wiggling a finger inside the bearing hole side to side, now that is time to change a new one.

Of course prolonged usage without packing enough grease is gonna result in bearings having all kind of play and rolling around the race especially those with lesser tolerance. That is certainly gonna affect bearing life as well. So at the end of the day for me it still boils down to packing it up but the "secret" lies in the choice of grease. Keyword: Viscosity
But remember not all grease are ok even if the viscosity is right... Make sure they do not contain stuff that will crap out the seals or in some cases the plastic retainers found in certain sealed bearings

Just to show the difference between a greased and lightly oiled bearing with seals removed...

1 comment:

  1. Ceramic ball bearings are the latest must have when it comes to some of the best bearings on the market. They are lighter, smoother, stiffer, harder and corrosion resistant as well as being electrically resistant. Thanks a lot for sharing with us...