BMW 3-Series Front Control Arm Interchangability – E30 vs. E36
Car Year: 1989
Car Model: 325is
I have heard that I can install M3 control arms on my E30 325is for better performance. Is this true?
Short answer; yes. Long answer: it all depends.
This information applies to:
E30 models (3-series 84-91, 318i, 318is, 318ic, 325, 325e, 325es, 325i, 325is, 325ix, M3)
E36 models (3-series 92-98, 318i, 318is, 318ic, 318ti, 323is, 323ic, 325i, 325is, 325ic, 328i, 328is, 328ic, M3 and 99 323is, 323ic, M3)
While the control arms for the various E30 models and the E36 models do indeed look similar, they are not all fully interchangeable. As for an increase in performance, this would be relative to just what swap was being done. The E30 M3 control arms are aluminum and will decrease the unsprung weight at each front suspension point, allowing the suspension to react quicker. Alternately, changing the caster angle can potentially increase turn-in (decreasing positive caster) or increase the high speed stability (increasing positive caster).
All E30 models (including the M3, which uses aluminum control arms), E36 non-M3 models and the 95 E36 M3 use the same control arm geometry. In other words, the arms are functionally interchangeable. For example; the 95 M3 or the E30 control arms can be used on the non-M3 E36 models in order to eliminate the rubber isolated outer ball-joints that are used on these models. NOTE: The Meyle Heavy-Duty control arms for the E36 models will also eliminate the rubber isolated ball-joints.
The 1996-99 E36 M3 control arms have a different geometry than all of the other E30 and E36 models noted here. The outer ball-joint is positioned 10mm forward of the positioning for the other 3-series models.
Note that the offset control arm bushings that are used on the E30 M3 and the 1995 E36 M3 are used to increase the positive caster. The 1996-99 E36 M3 accomplishes this by changing the control arm geometry (as noted above) and using centered control arm bushings.