Alrite here is what I got. This dimension is from the front axle take-up(thats what the manual called it) to the rear axle take-up. Its a diagonal dimension... I dont know if its exactly what you want. I wish I had a scanner at my moms house or else I would scan it.
This is exactly how it reads
2254,4 +/- 2,0 its all in mm's
<img src='http://img127.imageshack.us/img127/4284/bmwlogo2new17jy.jpg' border='0' alt='user posted image' />
Black 4 door 1990 325i
15"x7.5 Ronal LS-wrapped in 205/50-15 Bridgestone Potenza G009