Jon Schaer wrote:
> Message: 9
> From: "Jon M. Schaer" <jschaer@columbus.rr.com>
> To: <aantipas@sopris.net>, <classicrendezvous@bikelist.org>
> Subject: Re: [CR]bearing quality
> Date: Fri, 27 Dec 2002 16:03:16 -0500
>
> ----- Original Message -----
> From: "Andrew Antipas" <aantipas@sopris.net>
> >I noticed Bicycle Classics
> >lists loose ball bearing as grade 25 and the same quality as Campy. I
> >have seen other suppliers list grade 200 bearings. How are bearings
> >graded? Is a higher or lower number the better grade? Thanks for the
> >help!
> >
>
> The lower the grade the better the bearing quality. Grade 25 is normally
> the
> highest available, going through grades 50, 100, 200, and 500. I have seen
> one distributor that had grade 20.
>
> Campy bearings are also grade 25, but are supposedly matched sets from
> production runs, which theoretically would allow smoother running. I
> personally have only found a difference with headsets, I assume because the
> larger bearing race radius and greater distance between bearing sets
> amplifies race alignment error and the effects of bearing variance. Just on
> principle I use Campy bearings in all my top grade components anyway.
>
> Jon Schaer
> Columbus, OH
>
>
To expand on what Jon has touched on: what Campagnolo's bearing manufacturer (usually SKF in Sweden as far as I know) and others' do is sort for size within a range of maybe 100,000 or more Production parts, usually "low" "medium" and "high" for a specific size, such as 1/4-inch diameter. Then pre-sorted balls of matching spec. are used in a run of retainer-type bearings. In assembled ball bearings (e.g. "cartridge type"), there are often several categories of internal clearance for a specific bearing size/type that get increasingly small and also go negative as the price increases (negative clearance means that the bearing is "pre-loaded" - it can withstand higher loads and will be stiffer in that case - automotive wheel bearings are starting to be spec'ed that way to help increase chassis stiffness, for example). . If you get random Grade 25 balls and use them in a headset or BB, they will have quite a bit of diameter variation when compared to "matched" Grade 25 balls. The Grade just specifies permissible roundness and sphericity variation maximums, etc.
I'd run away very quickly from Grade 500 for bicycle bearings (or most anything) - 500 microns of variation is 0.5 mm - you can almost see that much!)
Regards,
Greg "con sfere" Parker
A2 MI USA