The E21 suffers from a front-end shimmy between 50-60mph. This plagued the E21’s reputation and led BMW to introduce a brand new front suspension design for the E30.
I’ll tell you about my car first and then get into the usual causes. My car had a shimmy from around 40mph and then it went away. It didn’t have the usual 55mph shimmy. I wasn’t too concerned about it since all of my focus has been on the engine swap.
Then on one of my test drives I realized the shimmy was completely gone! No shimmy at 40, 50, or 55. I completely expected there to be something because there were loose control arm bolts, ripped tie rod boots, and I don’t think there are any of the usual shims or stiffer bushing fixes commonly used (see below). The previous owner said he liked the handling “lively”. My guess is that the tires were slightly squared from sitting for a few months.
The shimmy has quite a few potential causes:
- the shimmy is inherent to the design because there is no locating link [solution: none other than full tubular A-arms]
- worn ‘outer’ control arm bushings where the sway bar connects to the control arm [solution: replace with Genuine BMW rubber or urethane]
- loose or worn wheel bearings [the wheel bearings should be re-tightened every 20k miles]
- bent wheel(s) [straighten or replace them]
- flat-spotted tires [drive on them for a while and they should re-shape themselves]
- worn sway bar bushings on the frame rails [replace bushings with rubber or urethane]
- wheels torqued to the wrong spec [loosen and then re-torque]
- the wrong wheels (the wrong center bore or bolt pattern) [confirm wheel specs. If these are the wrong wheels, replace them right away]
- bad strut or strut mount [replace strut inserts and mounts]
- worn steering rack bushings [replace with urethane]