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Old 08-26-2019, 10:32 AM
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Default Engine bearings

I am looking to replace my engine bearings, I was curious on everyone's thoughts on ceramic vs steel, abec 3,5 or 7 and front bearing seals
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Old 08-26-2019, 10:41 AM
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+1 wanting to know
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Old 08-26-2019, 11:00 AM
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Originally Posted by Breeze View Post
I am looking to replace my engine bearings, I was curious on everyone's thoughts on ceramic vs steel, abec 3,5 or 7 and front bearing seals
Ceramic is lighter then steel so less inertia. But ceramic is also much more expensive compared to a steel bearing. No real difference in lifespan.
I suggest steel because no real change in performance and if you need to change the bearings then you will be cheaper off.

Also I advice to use original bearings from the engine manufacturer if you want to play it safe.
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Old 08-26-2019, 12:20 PM
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The weight difference of ceramic vs steel balls will be meaningless if you realise that there is a huge rotating mass with the crankshaft and clutch and not to mention the whole drive train including the wheels behind it.
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Old 08-27-2019, 03:30 AM
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If I'm not mistaken it's a lot easier to make perfectly round balls from ceramic, so cheap bearings might actually be better as ceramic, in theory.
They also eliminate any micro welding, but as stated before, they usually don't last any longer anyhow...
And as Rody said, it's a lot safer to buy original bearings as they are usually matched better in tolerances for the crankcase, I've had some that was very loose causing the engine to surge. But I have also had good results with bearings like TKO, Avid etc.
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Old 08-28-2019, 04:30 PM
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So adding ceramic bearings shouldn't help with getting a few more rpms? With the front bearings will a double sealed bearing last longer than a single sealed bearing?
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Old 08-29-2019, 01:24 AM
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Originally Posted by Breeze View Post
So adding ceramic bearings shouldn't help with getting a few more rpms? With the front bearings will a double sealed bearing last longer than a single sealed bearing?
Adding ceramic bearings will not give you the engine more rpm.
double shielded bearings will prevent less dust going into the engine. The bearing-life itself will increase of no dust goes inside.
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Old 08-30-2019, 09:04 AM
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Steel bearings will last longer due to having a little more elasticity than ceramic. The power pulses of combustion are pretty brutal. Steel being softer will absorb those pulses a little better than ceramic. When I say steel, I refer to chromeoly steel. Stainless steel bearings work, but stainless is softer than chromeoly and usually don’t last as long.

As far as fit goes - use what fit the factory uses. Many use C3 fit, so I would typically suggest C3 fit. However, these fits are listed as loose bearings. The fit likely will be tighter when installed, so don’t use C2 fit thinking it’s better because it will be tighter yet when installed causing extra drag.
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Old 08-30-2019, 01:25 PM
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Originally Posted by SlowLST2 View Post
Steel bearings will last longer due to having a little more elasticity than ceramic. The power pulses of combustion are pretty brutal. Steel being softer will absorb those pulses a little better than ceramic. When I say steel, I refer to chromeoly steel. Stainless steel bearings work, but stainless is softer than chromeoly and usually dont last as long.

As far as fit goes - use what fit the factory uses. Many use C3 fit, so I would typically suggest C3 fit. However, these fits are listed as loose bearings. The fit likely will be tighter when installed, so dont use C2 fit thinking its better because it will be tighter yet when installed causing extra drag.
It's a bit more complicated than that, you have to look at both Dynamic and Static Load Rating.
Based on that, rpm, lubrication used etc you can get an estimated life expectancy.
Static Load Rating is probably more of an issue for the front bearing during start, and Dynamic Load Rating is the issue for the rear bearing during operation with high rpm (these engines isn't producing any alarming pressure levels even if you go by the exaggerated power numbers posted).
And you can get far more problems when you use materials of the same properties, that's why they mix materials in any engine of any size, you never want two identical materials rubbing or sliding at each other as that will wear out quicker then if one is softer, un-coated/hardened etc.
For some industrial purposes they even have mixed balls to combat these things, so they use a mix of steel and ceramic balls where the purpose of the ceramic balls is to even out the surface for/from the steel balls, and the overall condition doesn't require full ceramic.

But for these engines it's really not a problem and pretty much only theoretical as the environment they are subjected to has more of an impact and ceramics isn't really worth the price, though one might wonder if the coinciding introduction of more 100% synthetic oil and ceramic bearings might have something to do with each other...
Worth mentioning is that stainless steel that is sometimes used isn't good, according to some numbers they have about 80% or less life compared to any steel.
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Old 08-30-2019, 02:42 PM
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Originally Posted by NitroVein View Post
It's a bit more complicated than that, you have to look at both Dynamic and Static Load Rating.
Based on that, rpm, lubrication used etc you can get an estimated life expectancy.
Static Load Rating is probably more of an issue for the front bearing during start, and Dynamic Load Rating is the issue for the rear bearing during operation with high rpm (these engines isn't producing any alarming pressure levels even if you go by the exaggerated power numbers posted).
And you can get far more problems when you use materials of the same properties, that's why they mix materials in any engine of any size, you never want two identical materials rubbing or sliding at each other as that will wear out quicker then if one is softer, un-coated/hardened etc.
For some industrial purposes they even have mixed balls to combat these things, so they use a mix of steel and ceramic balls where the purpose of the ceramic balls is to even out the surface for/from the steel balls, and the overall condition doesn't require full ceramic.

But for these engines it's really not a problem and pretty much only theoretical as the environment they are subjected to has more of an impact and ceramics isn't really worth the price, though one might wonder if the coinciding introduction of more 100% synthetic oil and ceramic bearings might have something to do with each other...
Worth mentioning is that stainless steel that is sometimes used isn't good, according to some numbers they have about 80% or less life compared to any steel.
For the intellect level of most people on this forum, and used within our toy engines, this information is more than adequate. When too many facts are introduced, the “i Read...”, “I heard...”, and “So and So used these and...” responses show up skewing the facts. Unless someone has bonafide scientific evidence, it’s ALL theory and hearsay. I know what works for me, so I stick with what I know works and lasts. YMMV.

And FWIW - I have and do look at the spec sheets for bearings.
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Old 08-30-2019, 04:06 PM
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Face it, there is no RC bearing "manufacturer" who has detailed specsheets. And I wrote "manufacturer" because most small bearing companies do not even produce the bearings but just buy and resell them.
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Old 08-30-2019, 04:17 PM
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Originally Posted by SlowLST2 View Post
For the intellect level of most people on this forum, and used within our toy engines, this information is more than adequate. When too many facts are introduced, the i Read..., I heard..., and So and So used these and... responses show up skewing the facts. Unless someone has bonafide scientific evidence, its ALL theory and hearsay. I know what works for me, so I stick with what I know works and lasts. YMMV.

And FWIW - I have and do look at the spec sheets for bearings.
The whole point of me writing what I did was for this reason, I made clear what the actual numbers say if you do all the math, and also what the usual outcome is and how it can wary. It was far more than just a rant about it, it was based on the physics of the engine, knowledge on lubrication, formulas used by the bearing companies etc, and also the reality that when all comes around there is some things you can't calculate (like how people tune their engines, if they maintain them etc).
It's better to clear things up, but I'm swiftly saying things sometimes as well, so it wasn't personal in any way at all.
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Old 08-30-2019, 04:18 PM
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Yep. You’re right Roelof.

Last edited by RCTecher12; 08-30-2019 at 04:30 PM.
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Old 08-30-2019, 04:23 PM
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Sorry, I forgot.
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Old 08-30-2019, 04:42 PM
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Ever drop a ceramic bearing accidentally on the floor? Yep, might as well throw that in the garbage!

Even the slightest chip that bearing will eat itself alive in a hurry.

But, yeah, less rotating mass, and slightly more rpm due to less centrifugal friction. And they don't rust. Well, at least the balls don't, The cage however, that's another story.
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