Ceramic wheel bearings. Anyone tried these?

[orange4boy]

Just talked to my local bearing guys here and no joy. Sounds like a custom order for the Previa. If your car uses a standard bearing size you might be able to find them.

He knew very little about them but said they could be ordered in standard sizes.

More learning to do...

[Hasbro]

You'll always get good answers on Grassroots Motorsports Magazine

[cfg83]

orange4boy -

Originally Posted by orange4boy

Just talked to my local bearing guys here and no joy. Sounds like a custom order for the Previa. If your car uses a standard bearing size you might be able to find them.

He knew very little about them but said they could be ordered in standard sizes.

More learning to do...

I just looked mine up on flea-bay :

eBay Motors: 91-2002 SATURN "S" SERIES front wheel bearing NEW (item 320295375512 end time Sep-14-08 11:48:32 PDT)
sw_front_bearing.jpg

eBay Motors: 96 97 98 99 00 Saturn SL,SC Rear Wheel Hub Bearing (item 250292903432 end time Sep-16-08 04:00:09 PDT)
sw_rear_bearing.jpg

It looks like the front bearings are "standard issue", but the rear bearings are in a custom housing.

Question: Would front ceramic bearings help even if the rear bearings were OEM?

CarloSW2

[orange4boy]

The less friction the better but I don't have any numbers. I believe most cars have two sets per front wheel so that means 4x the friction savings but I'm thinking these are $$$$ bearings so the economics people are not going to like the numbers.

The losses are small on their own but would add up just like any ecomod.

I'm hoping the rollers can be replaced. I'll be doing the research this eve. or tomorrow. If bike wheels, computer fans and VW concept cars have them, I gotta have them.

[Ryland]

from what I have read you do run them with grease or oil in them so they do have some lube, but they reason they can run dry is that steel "sticks" to steel, this is part of why using bronze or brass as a bushing works, but their draw back is brass is soft, ceramic is extreamly hard, so even if you put it in steel races it will not stick to them causing that initial friction and wear that you need oil for.

mcmaster carr sell the plane balls that could be used in a bike, $3.55 each for 3/16" and I think a bike needs around 26 per wheel?

[tasdrouille]

As far as rolling resistance is concerned, bearings and seals account for roughly 13%. With tires inflated to max pressure that percentage goes up somewhat.

[pumafeet10]

you can also use ceramic for lots of other bearings such as in the trans, and what about the rotating assembly? Im sure lots of other stationary parts could make of ceramic? i might cost a little more but sounds like it would be worth it!

[Hasbro]

Originally Posted by tasdrouille

As far as rolling resistance is concerned, bearings and seals account for roughly 13%. With tires inflated to max pressure that percentage goes up somewhat.

Is this because some of the resistance is eliminated or that more stress is put on the bearings?

[trebuchet03]

Lets assume, for a moment, the data on this website is correct

Ceramic Ball Bearing vs Steel Ball Bearings





Now, lets say you're steaming down the road at 55mph with my wheel set (approx 24" diameter).
55mph is 4840 feet per minute and the circumference of my tires is ~6 (2ft*3).
That means, at 55mph, my wheels are rotating at ~806rpm

Lets now say 70mph - 6160 feet per minute which comes to 1027rpm.

The knee on the steel ball bearing doesn't occur until nearly 4K rpm - and the knee on ceramic doesn't happen until ~6K. Divergence between the two graphs doesn't really start to happen until 2K (really, probably not 2.5-3K).


Ceramic bearings shine in two areas
1) High Rpm
2) Longevity (mostly, at high rpm) - harder bearing
3) high temp operation
4) corrosion resistance

This is a case where yes, there will be some reduction. However, potentially not measurable and cost v. benefit is significantly out of proportion. Bearing losses are a somewhat significant portion of rolling resistance, but it looks like you're not going to find much reduction from ceramics.

Just for fun, any race car going 200mph (lets assume my wheels as I don't really know what diameters are used)
200mph = 17,600fpm... Wheels are rotating at 2933rpm.
So yes, ceramics look like they could be useful. Especially if they get hot due to heavy brake usage more common on a track versus on the road.


Oh, and I'm not saying you shouldn't do it... I'm just saying that these aren't the droids you're looking for.


-----
Yes, those are back of an envelope calculations and I'm well aware that pi!=3

[tasdrouille]

Originally Posted by Hasbro

Is this because some of the resistance is eliminated or that more stress is put on the bearings?

My reply was based on the reasoning that as you reduce the rolling resistance of one component the relative proportions of other components to total rolling resistance increase.

The correct numbers are:

Brakes: 6%
Bearings and seals: 12%
Tires: 82%

Assuming 32 psi in the tires.

It is estimated that rolling resistance in a tire is reduced by 7% for every 0.3 bar pressure increase (~4.35 psi). Pump those tires to 45 psi and the rolling resistance is reduced by roughly 20%. The numbers now become:

Brakes: 7.5%
Bearings and seals: 15%
Tires: 77.5%