Ceramic main bearings???


2 replies to this topic
  • ready fredy

Posted July 06, 2011 - 07:28 AM

#1

Hey guys i read in a recently old dirt bike magazine about a national enduro rider that the first thing he did when he bought a brand new bike was to replace the stock main bearings with ceramic ones because the vibration is much less.Has any one heard of these and the life span and if they are strong enough to use in these modern day four strokes? I never knew theses existed!

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  • grayracer513

Posted July 06, 2011 - 08:11 AM

#2

Ceramic bearings are usually made with a steel inner and outer race, same as normal cartridge ball bearings, but with ceramic silicon nitride balls in place of steel. The advantages to this are that the bearing can accelerate more quickly without skidding, they require less lubrication, the balls last longer (but the races don't), they run cooler, and yes, they vibrate less.

The first question is whether any of these factors are significant in the main bearings of a YZ450. Vibration, being the issue you raised, of a normal steel main bearing in a 27 cubic inch single cylinder engine is completely insignificant and unnoticeable among the much more intense rotary and reciprocal vibrations produced by the crank assembly itself. An experienced road cyclist or a competitive roller blade skater might notice the improvement. You won't.

As far as heat, lube, etc., consider that the main bearings in a YZF are probably the very last component that ever fails in the engine, so I don't think that the existing bearings are being pushed to anything like their limit.

Likewise, the speed and acceleration issue is something that really only comes into play beyond the speed range of the YZF in things like turbine shafts.

Then, at the end, there is the fact that the outer race design of the YZF main bearing is proprietary; there's a custom step cut into it for the bearing retainer plates. This would make ceramic bearings very difficult to even find.

Ultimately, are ceramic bearings better? On a theoretical level, yes. Is there any practical need? I very seriously doubt it.

  • Polar_Bus

Posted July 07, 2011 - 05:37 AM

#3

I personally never tried them. I am a true believer in OEM . However I have read up on a lot of credable racer feedback over in the kart racing forum reguarding ceramic bearings. For the most part in sustained high speed racing applications such as 12,400 sustained rpm Honda CR125 race karts there is some advantages to running ceramic crank bearings, slightly better longevity, less rolling resistance, but at nearly double the cost of OEM bearings, the generall sunday club racer was not seeing the cost effectiveness of the ceramics.





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