Hi Steve,

...not even the minimum thickness.

This is the only part of your post that grabbed my concern, otherwise I'd be in full agreement with the response you've so far received.

The minimum thickness figure is determined by the auto manufacturer, so should be identical. Maybe you weren't saying there are two different numbers, but just commenting on one's different placement of the numbers? Can you take rough measurements of diameters, thickness, offset and compare holes drilled?
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Art Benstein near Baltimore

Do you remember when you were a kid, playing Nintendo and it wouldn't work? You take the cartridge out, blow in it and that would magically fix the problem. Every kid in America did that, but how did we all know how to fix the problem? There was no internet or message boards or FAQ's. We just figured it out. Today's kids are soft.

Beck/Arnley doesn't manufacture anything themselves, so everything they sell is actually a repackaging of other manufacturers product's. You probably got rotors from two different factories, both of which had contracts with B/A. Personally I wouldn't be worried about the minor differences you noted. The machined away vane area is almost certainly from balancing of the rotor post casting and machining. That dynamic balancing is one sign of a quality rotor.

Historically B/A usually had top quality suppliers. The B/A sourced master cylinder I bought is actually an original ATE unit inside the box. It is absolutely identical to the one which came on our 240 originally. But, you never know for sure what you will get with B/A parts.

I think both the machining and weight differences (note I did not call them discrepancies) are
from balancing.
Remember that these are not high precision castings and if they were they would be more
expensive than you would likely be willing to pay.
I guess if side-to-side balance is an issue, you could put the lighter disk on the side where the heavier passenger rides.....
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George Downs, Bartlesville, Heart of the USA!