miamijim

You know how many Schwinn Air Dynes with bronze bushings I've over hauled? Hundreds. You know how many of them needed new bronze bushings?

Every one.

cny-bikeman

What you are saying is that you are willing to ignore the other variables, including the various tolerances and variables of cones, cups, cup seats, axles and threading, not to mention assembly and adjustment, in order to obsess about bearing diameter differences that "could" be significant, and that you admittedly just made up, because you once read something somewhere. If you insist on worrying I would suggest you never have bearings worked on in a shop - because they pour a new batch of loose balls in with the old ones, and that you replace all the bearings in any new bike with ones that are certified as being from the same batch.

Andrew R Stewart 

To piggy back on cny's thoughts (which I agree with) but for those who think bushings will be as good or better then a roller element bearing I suggest go ahead and make one. Then come back and give us your findings. Please track costs including time and the after test period break down and reassembly. Andy

FBinNY 

Yes, if limiting ourselves to the narrow question of how much functional difference it makes in a bicycle application, it makes little or any.

However, mixing lots takes the variance beyond the limits for the given grade, and essentially downgrades them. So, there's no reason to pay a premium for a higher grade (lower number) only to degrade immediately.

For those who may not understand this, keep in mind that the lot tolerance is tighter than the overall tolerance. It's kind of like buying paint. All of a specific brand's "burnt cinnamon orange" is the same color, but there will be subtle variations between production lots. This is why experienced painters buy all they expect to need in a single purchase from the same lot.

The question of mixing lots goes to the core of why they track production of many items, ie. paint and steel balls by lot.

Finally, we get back to the question of "best practices". While mixing lots probably doesn't make a difference, not mixing them is free and balls cheap enough. So, while there may not be much reason to avoid mixing lots, there's no valid reason to do so, and I for one, wouldn't trust a mechanic who tires to claim otherwise.

AnkleWork

You'll need matched grade 25 or better to prevent vibration (above 30,000 rpm).