6704-2RS (Enduro) Wheel Bearing
Inner x Outer x Depth (mm): 20 x 27 x 4mm
Used on: Specialized Roval Wheels
- Inner Diameter x Outer Diameter x Depth: 20 x 27 x 4mm
- Used on: Specialized Roval Wheels
- Precision Tolerance: ABEC3
- Ball Roundness : Grade 10
- Seals: 2RS (2 Rubber Seals)
- Grease: Low friction, temperature stable grease
- Material: 52100 High Carbon Chromium Alloy Races
- Note, This listing is for single bearings, and not pairs.
Why Choose Enduro Bearings?
Unlike others, Enduro bearings are not just ‘off the shelf’ Industrial bearings. They are tailored specifically for the demands of cycling. Every aspect of an Enduro bearing is considered and spec’d to provide superior performance and value for each application. From the material of the races and the ball bearings, the types of seal and even the grease. Each of these has a profound effect of the performance and longevity of a bearing.
What is ABEC?
The ABEC grade of bearings is a set of standards for the manufacturing tolerances of bearings. There are five classes from largest to smallest tolerances: 1, 3, 5, 7, and 9. The higher ABEC classes provide better precision, efficiency and greater speed capabilities, but do not necessarily make the components spin faster. All quality manufacturers around the world manufacture to at least ABEC 1 standard. Enduro’s Minimum Standard is ABEC 3.
What is the meaning of Ball Grade?
Bearing balls are manufactured to a specific grade, which defines its geometric tolerances (or roundness). The smaller the number the higher the precision. A grade 20 ball for instance is 20/1,000,000" out of round. Enduro use Grade 10 for ABEC 3.
At Enduro they utilize several types of grease depending on the projected application of the bearing. They also fill both sides of the bearing for maximum lubrication, unlike industrial bearings which are only single filled. Wheel bearings (usually 2RS or LLB suffix) contain a low friction, temperature stable grease, whereas a Frame Pivot Bearings (MAX type) will contain a thicker waterproof marine type grease.
2RS: Literally means the bearing has Two Rubber Seals. There are many types of seals. On most other bearings 2RS means that the seal is made from rubber and has one sealing lip rubbing on any flat part of the inner race. Enduro’s seals are usually either LLU (usually the MAX type bearings) or LLB (better for hubs).
LLU Seals: Two NBR 70 rubber seals with medium/high contact seal, which rides in a matching groove machined into the bearing to make a labyrinth type seal. The outer sealing lip repels dirt and water while the inner sealing lip retains the grease.
LLB Seals: Two NBR 70 rubber seals with low contact seal, which rides in a matching groove machined into the bearing for low drag or friction.
Bearing Installation and Removal
Bearings should never be installed by pressing on the inner race. Always press on the outer race with a pilot bushing or similar tool, which will only make contact with the metal side of the outer race. A bearing press or similar should be used to exert the force needed to press the bearing into the housing. Ensure that the seating surface is clean and free from rough edges so that they fit true and square. Quite often bearings can feel fine before fitting, but then feel "notchy" or "rough" after fitting. This is almost always due to the bearings not sitting square and true. Care needs to be taken that the bearing is started straight and not at an angle to the housing.
To prolong the life of your bearings, do not direct a high jet of water near areas of your bike where there bearings are located - an ingress of water can lead to premature bearing failure.
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