630 & 530 chain, what does it mean?

Chain type and size.
Chain comes in a variety of pitches and widths.  It is crucial to select the correct chain and sprockets for your bike.

The first number of the chain designates the chain pitch and represents the distance between each pin in eighths (1/8) of an inch.

630 chain is 3/4" pitch (or think of it as 6/8"), 530 chain is 5/8" pitch - so if you are not sure what size chain you have on your bike, just measure the pin-to-pin distance.

The second two numbers show the width of the roller section of the chain in eighth's of an inch with an assumed decimal point between the numbers.  So 630 chain is 3/8" wide and 525 chain is 5/16" wide (2.5 eighths).

520 5/8 inch pitch, 1/4 inch wide
525 5/8 inch pitch, 5/16 inch wide
530 5/8 inch pitch, 3/8 inch wide
630 3/4 inch pitch, 3/8 inch wide

O-Ring versus Non-O-Ring chain

The O ring in modern motorcycle chains protect the chain from moisture and dirt - both of which contribute to rapid chain wear.

The O-Ring style chains now come with a variety of different shaped O-Rings to provide more protection - The following pictures from RK Excel shows the different shape O-Rings used in chains today - the X and W profile O-Rings trap lubricating grease and help provide protection.

 There are several small disadvantages of the O-Ring chains:
- The total width of the chain is greater than non-O ring chain - the presence of the O rings spaces out the side plates and requires longer pins - this adds to the weight of the chain and can require spacers to ensure the wider chain clears the engine cases.  With a select few models (CB350F, CB500F and CB550F, you cannot use an o-ring chain due to the chain rubbing the transmission cover.
- The O rings create a small amount of drag on the chain that results in a minor performance loss at the rear wheel.

The big advantage of O ring chain is the greatly improved life of the chain - often doubling or tripling the life of the chain and sprockets over an equivalent non-O ring chain and sprockets.  You do still need to use a chain lubricant on the chain.  Match the chain lube to the type of chain.

Chain has different tensile rating - this strength rating shows how much force it would take to pull a chain apart - the higher the tensile rating, the stronger the chain. 

Motorcycle chain uses an alternating over/under link pattern.  Because of this, chain is always sold in even numbers of links.

Avoid putting non-motorcycle (industrial) chain on motorcycles, these chains are NOT designed for running at speed and enduring the harsh stresses put on them by a motorcycle.
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