How to choose a good Bearing for Roller Skating
Is ABEC the only thing that you need to know to decide how good a Bearing is for Roller Skating?
It Helps, and is a good general reference, but it is not the only consideration that you should know. Some of the BEST Bearings have a lower ABEC rating than their performance in Roller Skates would indicate. This is primarily due to the design of the Race Curvature allowing Axial Thrust.
Design Factors in Bearings
Ring Material (Inner and Outer)
Ball Material, Symmetry, and Consistency
Design: Operating Loads
Axial Play or Thrust
Shields & Seals
Audible Noise Level
The following are Factors in ABEC grades or ratings
1. Radial Runout Tolerance Requirements
2. Axial Runout Tolerance Requirements
3. ID Bore Tolerances (7mm for High Level Competitive Roller Skates)
4. OD Fit Tolerances (22mm for the Wheels)
5. Audible Noise Level
The higher the number, the better the bearing Tolerances are and the Quieter the Bearings run.
There are ABEC 1, 3, 5, 7, and 9.
Normally, Race Finish and Race Geometry are Superior in ABEC 5 and Higher
What makes a good Roller Skating Bearing?
1. Free Rolling with minimal Radial Play (which reduces the ball to ball load transfer).
2. Plenty of Axial Play or Axial Thrust. This is what allows a Roller Skate Bearing to work well. The tighter Axial tolerances of a higher ABEC Rating is not always what is needed for Roller Skating.
3. How much noise the Bearing makes is not of supreme importance. Bearing Noise is more often an indication of proper lubrication, or lack there of.
What is Radial Play?
Radial Play is the distance that one bearing ring can be displaced with respect to the other, in a direction perpendicular to the bearing axis or in easier terms is the free internal Radial looseness between the balls and the races, with no load applied to the bearing in any direction.
When a ball bearing is running under a load, force is transmitted from the outer bearing ring to the inner bearing ring through the balls. Since the contact area between each ball and the rings is relatively small, moderate loads can produce stresses of tens, even hundreds of thousands of pounds per square inch. These internal stresses have a significant impact on the life and performance of the bearing.
Factors that require control of radial play are speeds, loads, thermal conditions, mounting fits, axial motion and deflection rates. Improper selection of radial play can affect bearing torque and overall running performance which could result in premature failure.
A smaller Radial Play tolerance will allow the load to be more evenly distributed across the balls for optimal performance in a Roller Skate Wheel. Too much Radial Play will cause a ball to ball load transfer and “Under Load” this will slow the Bearing down.
What is Axial Play or Axial Thrust?
Axial Play or Thrust is the side movement of the inner race in relation to the outer race. Provisions in the Race Curvature and Contact Angle to allow a good amount of Axial Play or Axial Thrust are what allow Roller Skate Bearings to ROLL freely. This movement is very important because when Skaters push, we always put side load on the skate to get power in the push or stroke. If the Bearing does not allow for this, it will bind and LOOSE operating speed or ROLL.
What is the Cage and what Type of Cage is best for Roller Skating?
The cage, also referred to as the retainer or separator, is the component that separates and positions the balls at approximately equal intervals around the bearing raceway. Proper selection of a bearing cage is critical for meeting the load, speed and temperature requirements for Roller Skating. For Roller Skating, Brass or Stainless Steel Retainers provide the most roll, but also require the most care in cleaning and especially maintaining the lubrication properly so as to NOT let dry metal run against dry metal. A Snap Retainer of Synthetic or GlassFibre Reinforced Synthetic does not provide quite as much roll (but fairly close), and are much easier to maintain the cleaning and lubrication.
Roll-Line has introduced the Carbon impregnated Synthetic Snap Retainer. The Carbon J Snap Retainer provides some protection against under Lubricating the Bearing and increases the ROLL.
Are Shields and Seals Needed or Useful for Roller Skate Bearings?
Shields and seals are used in ball bearings to retain lubricants and prevent particulate contamination from reaching the critical surfaces. Shields are popular for most applications; seals are used where minimal clearance to light contact is required. Seals offer greater deterrence to particulate contamination, but increase torque and limit operating speed. My Grandfather “Mr. Charles Snyder”, founder of the Snyder Skate Company, did not believe in using shields because as soon as the shields were dinged or dented, they would bind and no longer ROLL as well. The shields also make a little harder to clean as well. Seals are somewhat common in today’s Roller Skate Bearings, but DO SLOW the ROLL. The suggestion is to just clean and lubricate the Bearings a little more often and especially before any big competition or event.
How to Handle and Work with Bearings
Ball bearings are very precise mechanisms that, in many cases, have geometrical tolerances measured in millionths of an inch. When handling, inspecting or mounting bearings, one should treat them as precision instruments. The user’s poor handling techniques cause most bearing failures.
Foreign particulate matter entering a bearing also shortens its life, and provides one or all of the following unsatisfactory operating conditions:
Lessened Lubricant Life
Keeping the external surfaces and contiguous components (i.e., Axle shafts, Truck assemblies, and Wheel housings) contamination-free is also important. Contamination on bearing faces or mating shoulder of the housings or shafts will cause a bearing pair to be out of parallel. This will cause the balls to run in a non-circumferential plane within the raceways, causing ball speed variations, ball skidding and binding between the races. These phenomena increase friction, which produces heat. Heat causes the lubrication to oxidize, resulting in premature bearing failure.
The following are a few suggestions to help eliminate contaminates from the Bearings:
1. Bearings should never be handled with bare hands. Talc-free finger cots or talc-free surgical gloves should be worn.
2. Work areas must be clean, clean, clean (no food or smoking should be allowed)
3. be sure to clean the wheel housings and axle shafts thoroughly before installing or mounting wheels.
4. Be sure to use a Bearing press that will install the Bearings Squarely into the Wheels. Force should be only applied to the outer race when installing the Bearings into the Wheels. Force should not be applied to the Bearings in a manner such that force is transmitted from one bearing ring to the other ring through the balls.
5. Be EXTREMELY gentle when pulling Bearings from Wheels, using the inner race. Rotate the wheel and bearing while extracting the Bearings. When pulling the Bearings, there is a great chance to damage the Bearings. Please be Careful.
What Kind of Lubricants work Best?
To get the high performance ROLL from your bearings it is suggested to use a light oil that has staying power in the Bearing. A thick oil or grease will slow down the bearings. Some oils on the market are Detergent based Oil’s. Some of these are 3 IN 1, WD-40, or even Uncle Charlie’s Magic Oil. These Oils are great if you are at a competition with no time or equipment to clean your bearings, put a few drops in and go skate, this will clean the Bearings out most of the time. A detergent based oil is probably not a good long term solution, but really works in a pinch.
We highly recommend SS-ROLL Oil from SkatesUS.com. SS-ROLL Oil is not detergent based and is a VERY GOOD Lightweight Oil that will stay in the bearings providing good Lubrication and ROLL.
Some of the included Information is from AST Bearings at www.ASTBearings.com and National Precision Bearing at www.NationalPrecision.com.