[jocko]

Yes, they can be ground a little. The problem is the definition of "a little". NObody really knows the thickness that remains, nor how much really "should" remain before strength is affected. One guy's approach may never cause a failure, but I'm not willing to be the "other guy" that goes veering hard left or right in a panic stop because my caliper housing just got overstressed and cracked. In other words, I doubt GM left a ton of extra material on there just to make it pretty, they are purpose built, and while it probably can be done without sacrificing overall integrity of the caliper - there's really no way to know if it has been sacrificed, unless it fails. Grinding off 2mm may not sound like a lot, unless the thickness there is already minimized to save weight - and that little 2mm of grinding now make sthe caliper susceptible to crack propagation. It comes down to a personal decision. You'll find a lot of folks aren't wanting to accept that unknown risk and that's why K5/10 wheels are at a premium. Don't get me wrong, I'm not saying it's wrong to grind a caliper housing, but it's one of those eyes wide open decisions someone has to make based on their own personal comfort level. It exceeds mine personally. In your case Tim, I'd agree, a casting seam probably has zero effect on part integrity. If min cross-sectional thickness in the area of the grinding is affected at all, that's when I'd start to have concerns personally.