None of us are professional car service technicians and this story is just my own experience, no responsibility implied, mess with your electrical system and your own BMW warranty at your own risk.

Props given to ReeYee and Skin Mechanic and Hugo for their seat bushing instructions, and most especially to Doug Whalen for making these sanity-saving bushings and other goodies!

Seat Rocking Shish Kebab
Thanks to JonT for company and pics and Shawn for all the work and the pics and the company and BBQing and to Melissa for company and dinner and turning me on to her Mac and Brent for the prototype shot and Beth for finding the Shish Kebab pic
and of course, the Z3 Owner/Inventors Doug Whalen, Shawn Fogg, Ron Stygar, Jon and Andy Maddux of LeatherZ.com - and WB and JonT for the Roundel scans.
updated November 3, 2007
update 12/17/06:
Apparently BMW has known about this problem since January 2000. They "improved" the "material on the isolator pad" we call the "bushing" but the seats still rocked. In November 2003 they quietly produced Service Bulletin 52 02 03, which has finally outlined the right names and BMW procedures for the replacement, but they still use the wrong "isolator pad material". As Mike Miller states, the key is to get the parts sold by Doug Whalen. The Service Bulletin is very helpful (and written with BMW "technical accuracy" as Mike Miller would like), but incomplete and incorrect.
update 10/30/07
Dave Tollison's powerpoint presentation of his install
(from bimmerfest)
from Roundel Magazine:
January 2005
August 2005

January 2007

Thanks Mike Miller!
please also join Z3Rides Email List via web or via email, meet all the people who worked on this page, and LOTs of Z3 owners who have done the modification are there to help you!

So your seat is rockin' and it's driving you crazy. This is not the rocking chair kind of rockin' there is another problem like that in our seats with another kind of fix. This is the feeling like your seat is sliding a little bit when you come to a stop, like a roller coaster loose on the rail. It may have been like that from the start in your car, it might have begun after some use, it might be a roadster or a coupš it might be an ///M or a Z3, doesn't matter year or model.
Well the good news is that there is a fix, the bad news is that it's a bit annoying getting to the part you need to fix.
Behold the elusive kebab:

Deceptively simple.
On top you see a kebab with original oem black rubber bushings, on the bottom you see one with Doug Whalen's white Delrin bushings. That is what it is all about, replacing the oem soft rubber bushings with hard Delrin bushings that won't "give".
I didn't think this would work because the rocking in my seats was so bad you could see it move, it felt like an inch of play.
This is it, rubber baby buggy bushings.
I checked my copy of BMW's Parts and Service Information CDs, albeit not the most recent, they don't show this part.
The closest I could come was 52 10 000 Removing and Installing front seat (normal/electric) left or right(Z3 Roadster M Roadster Z3 Coupš M Coupš)
Sport Seat Diagram
Standard Seat Diagram
So, there is no proper name for these parts. You are stuck with the names I give them. (See Update 12/17/06 for new proper names from BMW.)
Here is the best PARTS NEEDED list I can manage- please email me to update it
Materials needed:
Vacuum cleaner (when you see what's under your seat, you will want one, and maybe some nice carpet cleaning stuff too)
Socket Wrench -13 and 16mm socket for the seat rails. Then a couple of different sized torx bits to disassemble the rails.
Sandpaper (100 grit)
Sanding Block- so you can sand more evenly on the bushings.
Lug wrench
Block of wood to hold seat up while you work
12v power supply to move seat rails when seat is out of the car
Knee protection
Soldering iron- you may find torn wires
Nut and bolt tray
Blue Tape to mark where kebab is on rails
Work gloves- plastic and knit- for pulling door sills
mirror tool to see under the seats
4 Whalen bushings per seat (order from Doug's site, if site is not working, email Doug)
BFH (Rubber Hammer)
Midget 3/8" Drive Ratchet
since October 8, 2002
Seat Rocking Shish Kebab
Seat Rocking Fix:
Part 1 Behold the Kebab~~
Part 2 Remove the Seat~~
Part 3 Remove Seat Belt~~
Part 4 Check the Wires~~
Part 5 Free the Shish~~
Part 6 Shish KeBaba~~
Part 7 Disassembled Shish Kebab~~
Part 8 Sanding the Bushings~~
Part 10 Return of the Shish~~
Part 11 Rebuild the Pontoon~~
Part 11 Rail Motor Video ~~
Part 12 Drop Seat in Car ~~
Part 12 Drop Seat Video- Why this is harder in a Coupš ~~
Part 13 Reconnect Heat and Power~~
Part 14 Replace Belt & Seat~~
While the Seat is out:
Part 9 Remove the Door Sills~~
Part 9 Remove the Hump~~
Part 9 What's under the Floor~~
More Fun Toys:
Part 15 Ron Stygar Clutch Stop~~
Part 16 Doug Whalen Shift Knobs~~
Part 17 Fancy Cam Covers~~
Part 18 Beige Dot Leather Sport Seats~~
Part 19 The *only* Beige Dot Leather Console Lid~~
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