Stephen B. wrote:
> On the topic of Campy crank cracks, I was with a guy many years ago when
> he broke off his right campy NR crankarm. He came down on the TT pretty
> hard, which certainly spoiled his ride. He was a big guy, 250 lbs, and a
> very strong rider. He said it was the third Campy crank he had broken and
> refused to ride them ever again.
<snip>
Ouch! What other brand did he then break subsequently? :-)
<snip>
>
>
> On the bearing thread, I was once told that Campy kept significantly
> closer tolerances on their ball bearings than standard Grade 25 balls. It
> is also my understanding that Grade 25 bearings are made to spherical
> tolerance of +- 0.000,000,025 inch. I vaguely recall a claim that Campy's
> bearings where made to a spherical tolerance of 0.000,000,002 inch. There
> are other parameters that effect bearing quality as well, notably surface
> finish, but I wonder if anyone else was drinking the same beer I was in
> those days and had similar hallucinations? Anybody have a copy of
> the Bearing Cyclopedia handy and can look up the specs for Grade 25
> bearings? I do recall that I tried building up a Campy road headset with
> loose Grade 25 balls one time and didn't like the results. When I put a
> new set of Campy retainers in, that old Vicenza smoothness returned.
>
> <snip>
I think you are about a thousand times too good there in terms of bearing tolerance....
IIRC, Grade 25 bearings (generally the loosest commercial grade) are round to +/- 12.5 microns, or +/- .0000125" (25 millionths of an inch total tolerance), and Campy's spec. was about +/- 1.5 microns (tolorenzi di uno millesimo, or something like that...). If true, that equals grade 3 - way tighter than grade 25). Uniformity within a batch is also extremely important (bearing manufacturers sort for it, often creating "low," "medium," and "high" groups within a Grade), as are the mating surfaces and their positioning in space. I'll admit that my bearing-ese is a little rusty these days....
I've said this before, but Campy's bearings were so good because they came from Sweden!! (Also, they spec'ed 'em tight, tight, tight...).
I think Tullio spec'ed SKF bearings very early on in his career . I have an early Pista headset which has a navy blue box with an SKF logo on it - that's how proud he was of his choice of bearing supplier. They were undoubtably the most expensive available at the time, but guess what? They were the best! Back then, they were probably without peer in terms of surface hardness, roundness, general uniformity, and surface finish.
Today, there are manufacturers that are roughly equal to SKF in quality (FAG, NTN, NSK, to name a few). I would guess that Valentino has changed where he buys bearings to reduce cost. Anyone know for sure?
Regards,
Greg Parker
A2 MI USA