I am getting 292mm on ( http://lenni.info/edd/ )

Complete wheel data

Hub

• Formula - flip/flop
• Right flange ø: 62
• Left flange ø: 62
• Centre to right flange: 31.8
• Centre to left flange: 31.8
• Spoke hole ø: 2.7

Rim

• Mavic Open Pro (ERD is Mavic's Nipple Seat Dia + 3mm for nipples)
• Effective rim ø: 605
• Offset spoke bed: 0

Spoke length
for 32 spokes

Crosses Right Left Tension L/R
0 272 272 100%
1 274.6 274.6 100%
2 281.9 281.9 100%
3 292.4 292.4 100%
4 304.4 304.4 100%