09-23-2012, 10:16 AM
Join Date: May 2007
My Ride: 330i
Ok thanks, that makes sense about the part numbers. However, I am still not convinced about the quickness/tightness issue, and have to disagree with you there. Whenever I drive a ZHP, it feels like there is something about the "rack" itself. I know exactly what to expect from control arms, from shocks, etc. None of them add up to the steering feel of the beast
Originally Posted by TerraPhantm
The ZHP is *not* quicker. I've driven both. It is tighter, but the actual ratios are identical -- 13.7:1. This can be mathematically verified if you don't believe me.
I'm not saying the part was replaced with an updated version. I'm saying BMW simply doesn't sell brand new steering racks. They only sell refurbished/remanufactured ones. BMW often increments the part number by one for refurbished parts. The internals between the 650 and the 651 racks are the same.
If you google the 6 757 650 part, you'll find a lot of references to European cars such as the 318d, 320d, 330d, and guess what: these cars also have 6 757 651 listed as the steering rack part number. There's no super secret ZHP rack that BMW never documented.
There are other BMWs where the steering rack found on the car does not correspond to the part number listed in E46 (in fact, I imagine all of the are such). The E46 xi for example has a steering rack with "6 751 036" stamped on the sticker. The part number in realOEM is completely different (6759815)
I have also driven 02+ cars, that's I meant with "having owned/driven both".
Originally Posted by Alex323Ci
He had (back in '09) an '05 330i-zhp and NOW has an '01 330i. The '01 has the early 15.5:1 ratio. Of course it feels different!
Looks like you remember me just fine. Then you might also remember me participating in those discussions about the rack. I gave a break for a couple of years, and I'll give it to you, you guys look like you have made some progress about the part numbers, and what they mean.
What is still baffling to me is the steering feel of the ZHP. As I said above, the way I feel when I drive a ZHP forces me to isolate the feel as if it's the rack itself.
So I'm after what exactly is different on a ZHP rack. jpr at one point said it may be about its internal tolerances being tighter. Along these lines, I think it is very plausible that the M-Pack II internals might be the case here, as it does have specific part number for its rack.
And there is no research that has been done on this front, so I'd appreciate if you have something to post other than "part numbers", etc. Here's a thread that came very close to solving the mystery (which I have also participated back in 2008): http://www.bimmerfest.com/forums/sho...d.php?t=283973. People there talk about retro-fit kits, etc.
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