Yes..they can crack and yes they will break..eventually.
Luckily I felt this before it came apart. At first I thought it was just built up rubber..but after trying to clean them off by sliding the car around a bit (!!) the shaking was only getting worse...I came in to find this disaster waiting to happen.

https://photos.google.com/u/0/share/AF1 ... NJSGJRdDlB
Don't be stubborn..pit in if something doesn't feel right.
This is a Keizer billet aluminum center that has about 400 Whiskey Hill laps on it. No curbs..no offs..just a lot of flex cycles. I had magnesium centers before,which I managed to break..and replaced them with these billet units. I was told by Keizer these would not break. Wrong.
From people smarter than me looking at this failure, it appears to be more of a design issue than a material issue.

However..all things that are used and abused can break! Check your wheels.They are wear items.
I'll have to go to steel wheels in back. A little more weight..but much more durable..hopefully.
I guess I could slow down. Naaah...

Be safe out there!

