Me wrote:
> anyone know what "grade" xtr and DA are? are they more percise than 100 grade?
I don't know the direct answer to that but I'll x-post the question to
r.b.t. and here's some general info....
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from
http://www.sheldonbrown.com/gloss_ba-n.html :--
Bearing balls come in several quality grades, designated by numbers. Grade 25 is the best that is
available for bicycle applications. Grades 100, 200, even 300 are commonly used in bicycles.
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from
http://draco.acs.uci.edu/rbfaq/FAQ/8f.7.html :--
Following is a description of the different grades of ball bearings. The grade specifies the
sphericity of the balls in millionths of an inch. Thus, grade 25 are round to 25/10^6, while grade
1000 are good to 1/1000
(r.c. not all that round, but probably good enough for our uses).
Grade 25: the highest quality normally available, aka "Campagnolo quality": hardened all the way
through, best alloys, coatings, roundness, and durability. Evidently, a recent bottom-bracket
overhaul article in "Bicycling Plus Mountain Bike" magazine recommended these. Campy's tech reps
claim that the bearings in a set (usually in a little paper bag) are matched. One should not mix
bearings from different sets.
Grade 200: mid-range
Grade 1000: seems to be the lowest, may only be surface hardened.
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Note. If existing balls are shiny, they may not need replacing. See:
http://yarchive.net/bike/ball_bearings.html
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I'd be interested if you find out what grade Parker Int supply.
~PB