[DeTomaso] Campagnolo Paint preparation

[Garth Rodericks]

<<< So please educate me, why woiuld annealing them be a good thing? >>>

Because they crack! 


Magnesium castings, especially open-mold castings like our Campy wheels, tend to be porous, or at least have very large crystalline 

areas.  All wheels flex and bend 
slightly in use.  Magnesium flexes too, but the flex-energy is not 
dissipated completely.  Instead, 

stresses build up inside the castings, 
eventually concentrating at an imperfection such as a casting pore or a 
crystal grain.  Such an 

area will eventually separate and connect with 
another pore or weak spot.  A few more cycles of this and you have a 
crack growing in 

the casting, with the accumulated stresses 
concentrating at the point-ends of the crack.  This process works 
exactly like a micro 

pry-bar!

FWIW, when I stripped my wheels to refinish them I discovered one was cracked. Later tonight when I get home, I'll post a picture of an unusual and extremely dangerous crack that occurred on the inside rim hoop of a Campy that looked "perfectly good" from the front.


Here's an article from Jack DeRyke on the annealing process for Campy wheels:
http://www.realbig.com/detomaso/2000-06/1205.html

Cheers!
Garth