is the frame actually 130 spaced or is it a little smaller and putting a lot of pressure on the nuts?
edit: they crack because they are a harder steel to actually grip. thus making them a little more brittle. if they were softer they wouldn't break as often (its pretty common), but at the same time they also wouldn't bite in to your dropouts to hold your wheel in place.
is the frame actually 130 spaced or is it a little smaller and putting a lot of pressure on the nuts?
edit: they crack because they are a harder steel to actually grip. thus making them a little more brittle. if they were softer they wouldn't break as often (its pretty common), but at the same time they also wouldn't bite in to your dropouts to hold your wheel in place.