I did a quick search and it seems the most likely culprit for real fuchs cracking are ones that have been chromed. Thinking about my freinds "hose reel" fuch it is real shiny pretty, I'll try to check next time but I'm thinking it must be chromed.
I found this post on the bird:
QUOTE
C&P, post by 911/914gary:
OK… I work in the aircraft industry as a landing gear engineer. I work with a lot of exotic metals and plating processes. Here is the scoop on chrome plating and some basic facts on chrome. First, chrome does not change the base metal materiel properties such as material strength. It does reduce the material "fatigue life". Which means it won't last as long under sever loading and cracks. To reduce this effect we typically shot peen the surfaces to be chromed. This puts in a compressive layer on the surface that retards surface cracking (on the uncaoted substrate). Cracking can be induced from the second fact that chrome is porous. On the surface chrome has many microscopic cracks. Some of these cracks can go straight through to the base material. Thus the base material must be undercoated to protect it from corrosion. For aluminum parts we typically undercoat with copper or nickel. Finally the way chrome plates over edges or in fillets could create "stress risers". Thus the chrome must be masked or ground to a tapered or blended runout. So, why do we use chrome if it so difficult to work with? Chrome provides a hard protective working surface. On landing gears this is particular to dynamic or static sealed surfaces for hydraulics, under bushings and on static & dynamic pins & joints. Typically chrome on automotive wheels is for cosmetic purposes and probably does not have these extra processes. However, I'm sure these wheels are over designed for street use by the Porsche engineers. The probable cause of most of these wheel failures is stress corrosion failure initiated by a pit or crack through the chrome. If the wheels are chromed they should probably be surface clear coated to protect them from corrosion immediately after plating. Once corrosion begins there is no way to stop it. And the only way to check for corrosion is to strip the chrome. I probably would not use chrome plated wheels for the track.