Manual-Wheelchair bearing-nomenclature revealed

[chasmengr]

After reading on this forum about some confusion regarding bearing nomenclature (and being confused myself), I did some internet research.

Having spent years before my injury maintaining bearings as an avid rollerskater (inside and outside) and trailer boater (regular weekend submersion of wheel bearings), I am led to share what I've learned - for what it's worth.

Annually I would clean and repack my bearings (16 inside skate bearings, 16 outside skate bearings, and 4 boat-trailer bearings), all of which which required considerable disassembly. I plan to do the same on my wheelchair even more often because I boated and skated outside for only 3 months/year, and inside skating was done on regularly swept floors.

Bearing sizes -
bearing search engine (by size: ID/bore, OD, thickness/width)
Another bearing search engine

Example size nomenclature (based on TiLite who provides bearing dimensions):
"608" = 8mm x 22mm x 7mm (common wheelchair caster (dual-fork) & rollerskate/skateboard bearing)
"R8" = 1/2" X 1-1/8" X 5/16" (common wheelchair fork-stem bearing (dual & mono))
"R6" = 3/8" x 7/8" x 9/32" (common wheelchair caster (mono-fork) bearing)

Shielded verses Sealed bearings:
Discussion1 Discussion2
Nomenclature:
"2RS"= sealed on both sides ("RS" = sealed on only 1 side)
"ZZ" = shielded on both sides ("Z" = shielded on only 1 side)

Example of a full bearing model number: "R6-2RS" = 3/8" ID x 7/8" OD x 9/32" Thick bearings sealed on both sides.
(Note: This nomenclature indicates neither bearing material nor ABEC rating (if any); discussing those would require another posting.)



Extra credit: Standard Skate Bearing Sizes (industries other than wheelchair makers use a variety of bearings, too)

[totoL1]

Originally Posted by chasmengr

Shielded verses Sealed bearings:
Discussion1
)

This thread was helpful for me, i`ve got a hibrid ceramic bearings, it`s a
S608-2RS

I bought a pack of 8, so i`ve got 4 left for replace them in a future, i thought that they didn`t need any maintainment, but reading at your discussion 1 i saw the pic of how to remove the sealed rubber, and how to clean an lubricate them with Aral Aralub oil, i`m Spaniard, so i don`t know what is the equivalent of that in Spain, so could you give me a link of where to buy a little bottle of that, because this bearing aren`t cheap and i would like to lengthen their life all as posible.

I have riding with them around 3 monthes and they still spining nearly like the first day, but this ceramic balls make a bit noise and i have notice that they make now a bit more noise than when was new.
So, maybe is the time to clean and lubricate them with that Aral oil?

I thought that the ceramic bearing was white, but after have a look of how to remove the sealed part, i did it in one of the others i have left and i get a surprise when i saw they are black ceramic(Silicon Nitride)

[chasmengr]

Originally Posted by totoL1

This thread was helpful for me, i`ve got a hibrid ceramic bearings, it`s a
S608-2RS

I bought a pack of 8, so i`ve got 4 left for replace them in a future, i thought that they didn`t need any maintainment, but reading at your discussion 1 i saw the pic of how to remove the sealed rubber, and how to clean an lubricate them with Aral Aralub oil, i`m Spaniard, so i don`t know what is the equivalent of that in Spain, so could you give me a link of where to buy a little bottle of that, because this bearing aren`t cheap and i would like to lengthen their life all as posible.

Very glad you found it helpful.

I have never owned nor maintained ceramic bearings. I would like to think the oil sold on that same site is the oil you need.

Somewhere during my research I read that ceramics require very little oil unlike steel, which should be packed full of grease.

[totoL1]

After have reading this and see that they say that their life are 10 times longer than with steel balls, now i don`t think they are expensive.



Question : What is the advantage of Ceramic ball bearings?
Answer : Ceramic bearings have the normal steel balls replaced by black ceramic balls.
The ceramic balls are made of solid Silicon Nitride. Ceramic silicon nitride balls are called ceramic but have nothing in common with household dish ceramics. They are called ceramic because it's easier calling them ceramic then Silicon Nitride. The ceramic ball is by far, smoother, harder, lighter and stronger than one made off steel.



The following is a list of benefits of the ceramic Silicon Nitride ball bearing -

• LIGHTER. The ceramic ball is lighter then the steel ball. This means that the ball exerts less force outward against the outer race grove as the bearing spins. This reduction in outward force reduces the friction and rolling resistance. The lighter ball allows the bearing to rev up faster, and uses less energy to maintain it speed.
• HARDER. The ceramic ball is harder then the steel ball. This gives you a bearing that will last up to 10 times longer then the steel ball bearing because it holds it's spherical shape better.
• SMOOTHER. The ceramic ball has smoother surface properties then the steel ball. This means less friction between the ball and bearing races giving you a faster spinning bearing.
• THERMAL. The ceramic ball has better thermal properties then the steel ball. The ceramic ball will not heat up like a steel ball. This helps avoid heat build up in the bearing, a primary culprit in skate and skateboard bearing performance degradation.
• LUBRICATION. The ceramic balls are impervious to oxidation, chemicals, and require essentially no lubricant. The bearings are lubricated with a very, very small amount of Aral Aralub oil, not a gel or

[chasmengr]

If the 10x life holds true, they are less than 1/2 the cost of steel bearings.

[Foolish Old]

The life expectancy of the bearing balls is not the main concern in all cases. In the marine environment where I live, the surfaces of the inner and outer race that contact caster and axle are more likely to be the issue due to rapid corrosion. Salt air eats most stainless steel as a snack. Even premium alloys have limited life. Fork bearings do the same with the surfaces that contact fork housing and fork stem. I would think that active users who live where winter sidewalks and streets are treated with road salt might have similar wear patterns in winter. For me, it works better to have frequent changes of less expensive bearings. It's like sneakers. Country kids wear out the uppers of their sneakers. City kids wear out the soles.

Of course, toto.1 and others who demand bleeding edge performance from their chairs have far different concerns.

[radio_buddha]

Structure of bearings: http://www.youtube.com/watch?v=k8SHK...ure=grec_index

Cleaning of bearings: http://www.youtube.com/watch?v=GgbWh...eature=related

My bearings: http://www.youtube.com/watch?v=cVAUgOQJXeM

[Foolish Old]

I've seen a number of videos with casters spinning in free air for extended periods of time. Translated to real world use conditions of normal use - under load and with friction between tire and pavement - is the practical difference between a decent bearing and a high end bearing noticeable? I'm not talking about uses like the making of toto.1's fascinating downhill run video, but rather the low r.p.m. travel of the majority of users. This is not a rhetorical question, but one that I've thought about for some time and still don't know the answer. Seems like there are so many other factors that affect rolling resistance in every day use that bearing differences would be negligible assuming the bearings performed to an expected minimum standard.

[Edinburgh Colin]

Originally Posted by chasmengr

Very glad you found it helpful.

I have never owned nor maintained ceramic bearings. I would like to think the oil sold on that same site is the oil you need.
Attachment 37231
Somewhere during my research I read that ceramics require very little oil unlike steel, which should be packed full of grease.

Got to say that's an unfortunate name for a product, especially when placed in a sentence with the word balls as well,

Sorry must just be having a smutty innuendo moment!

[graybeard]

You can get bearing grease from roller hockey websites. I use the BSB spray lube for quick on the go work. Also can use the Bones Speed Grease for the death-defying runs for Toto-1. My boys go through bearings each year from their roller hockey seasons, so kinda old pro at this.

As for friction-resistance of different bearings, you would notice on smoother surfaces than rough terrain. If thats worth the difference, then use them. I use the boys old bearings, and they do jus fine. I do clean mine once every few months, as they collect quite a bit of dirt at the plant. I will use the heavier grease then to grease up the bearings. Mainly I do this for maintance only, not for speeding down the road.