Hello Richard - The double row ball usually has a brass cage and the single row is usually a steel cage. As the purpose of the cage is to keep the balls apart I would not trust polymide especially on my wheels. If anything happens to them whilst riding it could result in a nasty accident. They are no doubt designed not to fail but shit happens.........If a magneto bearing jams the engine stops and a walk may be necessary - if it's a wheel bearing whilst motoring it could be worse. Just call me old fashioned. Cheers, Howard
Hello Richard - The double row ball usually has a brass cage and the single row is usually a steel cage. As the purpose of the cage is to keep the balls apart I would not trust polymide especially on my wheels. If anything happens to them whilst riding it could result in a nasty accident. They are no doubt designed not to fail but shit happens.........If a magneto bearing jams the engine stops and a walk may be necessary - if it's a wheel bearing whilst motoring it could be worse. Just call me old fashioned. Cheers, Howard