Re: [CR]Cartridge Bearings

Example: Component Manufacturers

Date: Fri, 25 Jun 2004 10:22:24 EDT
Subject: Re: [CR]Cartridge Bearings

> I will have to look for my old book "Bicycle Science" by a bunch of MIT
>grads. They did a test of the rolling resistance of a bike with tight
>bearings and one set up right and guess what no difference. I find it hard
>to believe but the test looked good to me. I know it has to be some
>difference but apparently not enough to measure it. I know when you feel it
>with your hands it feels like it must slow you down but by the time you get
>that bike moving it just does not slow you down.

I'd love to hear more on this topic... Common sense says that since steel has a certain amount of elasticity and compressability, a bearing which feels a bit tight and does not spin freely when twirled in the fingers would perform better when placed under load and gets a few microns of additional clearance due to the pressure of that guy stompin' on the pedals. I also would imagine the properties of grease would be quite different when under a heavy load than when just being spun (perhaps similar to when the ice under a skater's blades turns to water for a fraction of a second from the pressure).

In Harvey's message where he quoted the advice of Jim Papadopolulos, about seal friction being the bigger part of bearing friction when spun in the fingers, and a lesser part when under load... you know that makes perfect sense too... but even though it is a difference of degree, the fact remains that the seal friction does not go away even if it becomes a smaller component of overall friction. I wonder how much energy is expended by a rider on a modern bike over a long distance due to the combined seal friction of BB, hubs, pedals, etc.? I think of this every time I spin a nicely-adjusted Campy pedal and then (try to) spin a new Look pedal with those tight seals.

Bob Hovey
Columbus, GA