3 Things you need to 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, while holding the outer ring and moving the inner ring in a radial motion you will notice a small clearance between the two rings. All bearings have this movement, there may only be a small amount of movement but is controlled by international standards. C3 and above means that the bearing has more play than normal and C2 means that the bearing has less play than normal.

C2 - Less play than Normal (0-0.009 mm)
CN - Normal bearing clearance (0.005-0.02 mm)
C3 - Greater than normal bearing clearance (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 which bearing clearance should you have?

C3, C4 and C5 bearings are bearings that have an additional 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 outset, e.g. where knives and inserts are aligned.

Applications such as motorcycle wheels or bicycle wheels do not require C3 marked bearings. Unless the bearing you are replacing specifically says C3 on it, you should not replace it with a C3 bearing, C3 bearings are loose to the touch from new and often people complain that the bearing is bad and has more movement than what they are replacing. C4 and C5 are even looser than C3 bearings. This is characteristic of these higher than normal clearance bearings labeled C3, C4 and C5.

C2 marked bearings have smaller internal clearances than standard bearings and should only be used in applications that specify C2 bets.

2. What does ABEC mean?

ABEC stands for Annular Bearing Engineering Council, which is a standard for defining the tolerance and precision of ball bearings. The tolerance of a ball bearing depends on how much the precision, based on an absolute dimension, can vary during manufacture.

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

How ABEC ratings work for skateboards and rollerblades

ABEC ratings are just odd numbers and start with ABEC 1

ABEC 1 is the most raw, 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 don't roll as smoothly or quickly.
ABEC 5 bearings are the standard for skateboards. You get a reasonable speed and at a reasonable cost.
ABEC 7 bearings would be very fast and smooth, but they are expensive. In addition, you start to risk damaging them unnecessarily 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 if you're going downhill or anything else where your goal is to go insanely fast. Unless you're spending a fortune on these bearings, don't trust that they're 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 to buy?

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

If too much friction is created, the layer will get hot and may break prematurely, so you need a layer that offers less friction. Bearings that offer less friction can usually withstand higher speeds because they do not get as hot.

Then it depends on what material the layer is made of, whether the outer or inner web is made of any other material than steel.

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

Benefits of non-contact bearings

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

Guidelines for seal selection SKF Deep groove ball bearings

Symbols: +++ excellent, ++ very good, + good, o acceptable, - not recommended (most common for SKF)

Requirements	Z	RZ	RSL	RST	RSH	RS1
Low Friction	+++	+++	++	++	O	O
High Speed	+++	+++	+++	+	O	O
Retention of fat	O	+	+++	+++	+++	++
Protection against dust	O	+	++	++	+++	+++
Protection against water Static Dynamic High pressure	- - -	- - -	O O O	+++ + O	+++ +++ +++	++ + O

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We will update the information as it becomes available. If you have any comments where you think we have worded it wrongly or tips on other important details we could rewrite, please send an email to info@remlagret.se