A brief guide to bearings: Difference between revisions
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This is some general information on bearings. It is not specific to the EX250, or even to motorcycles. The following information applies to bearings that have a rolling element (balls or rollers), not [http://www.frostytech.com/articleview.cfm?articleid=193&page=2 sleeve bearings]. | This is some general information on bearings. It is not specific to the EX250, or even to motorcycles. The following information applies to bearings that have a rolling element (balls or rollers), not [http://www.frostytech.com/articleview.cfm?articleid=193&page=2 sleeve bearings]. | ||
== | ==Definitions== | ||
*Outer ring: the outer part of the bearing | *Outer ring: the outer part of the bearing | ||
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*Cone: the inner ring with rollers and cage of a Timken bearing | *Cone: the inner ring with rollers and cage of a Timken bearing | ||
==General Information== | |||
*Most ball bearings have metric dimensions; it doesn't matter where the machine they are in was made. The last two numbers of the part number times 5 gives the bore (id) of the bearing on sizes that have a 20mm bore and larger. Example: A 6305 bearing has a 25mm bore. 5x5=25. A 6209 has a 45mm bore. 9x5=45. (This does not apply to tapered roller bearings.) | *Most ball bearings have metric dimensions; it doesn't matter where the machine they are in was made. The last two numbers of the part number times 5 gives the bore (id) of the bearing on sizes that have a 20mm bore and larger. Example: A 6305 bearing has a 25mm bore. 5x5=25. A 6209 has a 45mm bore. 9x5=45. (This does not apply to tapered roller bearings.) | ||
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*"Internal clearance”, or fit: Many people get confused when they find out that a bearing can be ordered with different internal clearances (which is the space between the races and the rolling element) and think that one is better than another. A ball bearing is usually supplied with either "normal" or "c3" internal clearance. A ball bearing with "c3" fit simply has more internal clearance (space) than a bearing with "normal" clearance. | *"Internal clearance”, or fit: Many people get confused when they find out that a bearing can be ordered with different internal clearances (which is the space between the races and the rolling element) and think that one is better than another. A ball bearing is usually supplied with either "normal" or "c3" internal clearance. A ball bearing with "c3" fit simply has more internal clearance (space) than a bearing with "normal" clearance. | ||
:You can use either when replacing a bearing. The main thing to remember is that THE QUALITY IS THE SAME. If given a choice, use the c3 fit; it has more internal clearance to allow for expansion from heat and improper shaft and housing dimensions. | :You can use either when replacing a bearing. The main thing to remember is that THE QUALITY IS THE SAME. If given a choice, use the c3 fit; it has more internal clearance to allow for expansion from heat and improper shaft and housing dimensions. | ||
*Ball bearings can be open | *Ball bearings can be open or have a seal or shield on one or both sides. The dimensions are the same as an open bearing. If a bearing has a seal/shield on both sides, it does not have to be re-lubricated. The lube that comes from the factory is designed to last for the life of the bearing. This does not mean that a high pressure washer will not blast water in and grease out, so avoid a direct blast from a car wash if you use one. | ||
==Replacement bearings== | |||
*A replacement bearing is often less expensive from a bearing distributor than from a motorcycle shop. The best way to identify a bearing is with the part number that is stamped on the bearing, not an OEM item number. Call a distributor, give him the part number, and add any information that may help, such as “a 6305 bearing with a seal on one side”. | *A replacement bearing is often less expensive from a bearing distributor than from a motorcycle shop. The best way to identify a bearing is with the part number that is stamped on the bearing, not an OEM item number. Call a distributor, give him the part number, and add any information that may help, such as “a 6305 bearing with a seal on one side”. | ||
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*Note on Timken bearings: A Timken cone will fit several different cups, and a cup will fit several different cones, so you have to need the cup and cone part numbers. | *Note on Timken bearings: A Timken cone will fit several different cups, and a cup will fit several different cones, so you have to need the cup and cone part numbers. | ||
==Installation== | |||
*Rule of thumb: The rotating bearing ring will normally be an interference (or press) fit, and the stationary ring will be a slip (not sloppy) fit. For example, the outer ring on a wheel bearing (the wheel rotates) is a tight or press fit, and the axle slips through the inner ring. The inner ring on an electric motor shaft (rotating) is a press fit, and the outer ring is a slip fit into the end bell of the motor. | *Rule of thumb: The rotating bearing ring will normally be an interference (or press) fit, and the stationary ring will be a slip (not sloppy) fit. For example, the outer ring on a wheel bearing (the wheel rotates) is a tight or press fit, and the axle slips through the inner ring. The inner ring on an electric motor shaft (rotating) is a press fit, and the outer ring is a slip fit into the end bell of the motor. | ||
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*Never use a brass hammer or brass bushing to install a bearing. It can chip and leave a small brass particle in the bearing. | *Never use a brass hammer or brass bushing to install a bearing. It can chip and leave a small brass particle in the bearing. | ||
==Quality== | |||
*The major bearing manufacturers all have factories in several countries, and the quality from each is excellent. These include SKF, Timken, Torrington, Fafnir, NSK, NTN, RBC, McGill, and a few others. Most of these companies use bearing grade steel that is made by Timken, even though they are competitors of Timken. | *The major bearing manufacturers all have factories in several countries, and the quality from each is excellent. These include SKF, Timken, Torrington, Fafnir, NSK, NTN, RBC, McGill, and a few others. Most of these companies use bearing grade steel that is made by Timken, even though they are competitors of Timken. | ||
*Avoid bearings from China, Korea (KBC) and third world countries. | *Avoid bearings from China, Korea (KBC) and third world countries. | ||