3 Things You Must Know Before Buying a Ball Bearing

1. What do the suffixes C2, C3, C4, C5 mean?

The C in the designation stands for internal clearance, which means that the bearing has room for expansion if needed between the bearings. When you hold the outer ring and move the inner ring in a radial motion, you will notice a small clearance between the two rings. All bearings have this movement, it may just be a small amount of movement but is controlled by international standards. C3 and above means that the bearing has more clearance than normal and C2 means that the bearing has less clearance than normal.

C2 - Less bearing clearance than Normal (0-0.009 mm)
CN - Normal Bearing Clearance (0.005-0.02 mm)
C3 - Greater bearing clearance than Normal (0.011-0.025 mm)
C4 - Greater bearing clearance than C3 (0.018-0.033 mm)
C5 - Greater bearing clearance than C4 (0.136-0.192 mm)

But what clearance should one have?

C3, C4, and C5 bearings are bearings that have extra internal radial clearance to cope with high-speed environments where excess heat is generated. They are not suitable for environments where critical alignment is required from the start, for example where Knives and cuts are set against each other.

Applications like motorcycle wheels or bicycle wheels do not require C3-rated bearings. Unless the bearing you are replacing specifically says C3 on it, you should not replace it with a C3 bearing. C3 bearings feel loose from new and people often complain that the bearing is bad and has more movement than the one they are replacing. C4 and C5 are even looser than C3 bearings. This is characteristic of these higher than normal free-running bearings marked C3, C4, and C5.

C2-rated bearings have less internal clearance than standard bearings and should only be used in applications that specify C2 clearance.

2. What does ABEC mean?

ABEC stands for Annular Bearing Engineering Council, which is a standard for defining the tolerance and precision of Ball Bearing. The tolerance of a Ball Bearing depends on how much the precision, from an absolute measure, can vary during manufacturing.

Ball Bearing graded with the ABEC system are often called "precision ball bearings" and they are graded on a scale with the numbers 1, 3, 5, 7, and 9. The higher the number, the greater the standard precision. There are no requirements for what material the ball bearing should be made of. The ball bearings just need to be made to a certain degree of precision.

How ABEC ratings work for skateboards and rollerblades

ABEC ratings are only odd numbers and start with ABEC 1

ABEC 1 is the rawest, least precise, most durable, and cheapest.
ABEC 3 is what most cheap complete skateboards come with, especially skateboards from China. ABEC 3 bearings work for most skateboards but do not roll as smoothly or quickly.
ABEC 5 bearings are the norm for skateboards. You get reasonable speed and at a reasonable cost.
ABEC 7 bearings would be very fast and smooth, but they are expensive. Additionally, you start risking unnecessarily damaging them if you ride hard or aggressively. Note that some cheap foreign-made ABEC 7 bearings may not deserve this rating.
ABEC 9 and higher would be ridiculous to use on a skateboard unless you're riding downhill or something else where your goal is to go insanely fast. If you're not spending a fortune on these bearings, don't trust that they are actually ABEC 9 you've got.

ABMA/ANSI Std. 20	ISO 492	DIN 620	JIS B 1514
ABEC 1	Normal	P0	Class 0 Class 6X
ABEC 3	Class 6	P6	Class 6
ABEC 5	Class 5	P5	Class 5
ABEC 7	Class 4	P4	Class 4
ABEC 9	Class 2	P2	Class 2

3. What does friction mean and how does it affect which bearing I should buy?

Friction is in physics a force that strives to counteract the relative motion between two surfaces that are in contact with each other.

If too much friction is created, the bearing becomes hot and can break prematurely, and then you need a bearing that offers less friction. Bearings that offer less friction can usually handle higher speeds because they don't get as hot.

It also depends on what material the bearing is made of, if the outer race or inner race is made of something other than steel.

If you want a low-friction bearing or non-friction bearing, you should buy an open bearing or a metal-sealed one as they offer just that. At the bottom of the page, you will find guidelines for SKF's sealing choices.

Advantages of non-contact bearings

Compared to standard bearings, low-friction bearings reduce the frictional movement by 30% or more. This reduces surface degradation, which decreases the risk of machine failure

Guidelines for sealing choices SKF Deep Groove Ball Bearings

Symbols: +++ excellent, ++ very good, + good, o acceptable, – not recommended (most commonly occurring for SKF)

Requirements	Z	RZ	RSL	RST	RSH	RS1
Low Friction	+++	+++	++	++	O	O
High Speed	+++	+++	+++	+	O	O
Grease Retention	O	+	+++	+++	+++	++
Dust Protection	O	+	++	++	+++	+++
Water Protection Static Dynamic High Pressure	- - -	- - -	O O O	+++ + O	+++ +++ +++	++ + O

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We will gradually update the information. If you have any comments where you think we have formulated it incorrectly or tips on other important details we could write about, send an email to info@remlagret.se