Based on the 14mm diameter of the shank, you need an absolute minimum of 6 turns of the bolt, preferably 7. When I ran 10mm spacers on the rear of my '04, I only got 5 turns with the stock bolts which is why I got longer bolts, 55 or 55mm if I recall. No longer use the 10's in the back and went with the H&R 25mm that bolts to the hub, and wheel bolts to the spacer with the stock bolts.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R