In Reply to: recirc ball steering question? posted by joe on December 07, 2000 at 19:16:32:
It's on the M5 'cause it's on all other E39 V8s.
It's on the E39 V8s because they use a front subframe and suspension design borrowed from the E38 (current 7-series), and the E38 uses recirculating ball.
Now, as to why the E39 V8 cars use the E38 front subframe: at the time the E39 was being designed neither the E38 nor its M60/M62 V8 engine had gotten to production yet.
I doubt E39 V8s were expected to account for even 5% of E39 sales (it doesn't in the European market), so there was a lot of pressure to do the design as economically as possible.
The right technical move? Maybe not. The right business decision? Probably.
In the end, the V8 car has sold very well (at least in some markets) so BMW could have spent the money to redesign the V8 oil sump and pump to accommodate rack-and-pinion steering. But world economies are generally a fair bit stronger than what BMW product planners were looking at in 1991, and hindsight is always 20/20 as they say.