[HerrK]

Rolf,

When you have gone as far as you can with the wheel in one piece. Here's what I would do.

1. Drill a hole (1/8 -1/4" Dia) at the end of the crack to keep it from propagating during the removal process.
2. Cut the crack out of the wheel using a band or sabre saw. Cut 1" or so away from the edge of the crack all around so you end up with a basic rectangle portion with a crack in it.
3. Match mark each side of the crack in at least 2 locations.
4. In line with the crack cut from the removed cut edge towards the hole drilled in #1. Which will now give you the two cracked halfs.
5. Using a magnifying glass 10X or more. Examine the crack starting at the rim edge. A jagged tearing of the metal, near the rim edge, may indicate a rapid fracture. If the crack initiation point is smoothed it may indicate a slower fatigue type fracture, unfortunately it my also indicate the two halfs were working against each other after failure and smothed themselfs. You can also examine the entire length of the crack for material voids/porosity.