I have an '89 535i with 18" Niche pultec wheels. I had the upper control arm bushings replaced about 6,000 miles ago. The shimmy has returned. Should have the bushings worn so quickly, especially considering I am running 18" wheels? I heard the right way to fix it is by using 750 series bushings. Is this true, and will it cure the problem for good? Also, my front tires are wearing more on the outside edges, and I did have a wheel alignment done after adding new H&R sport springs and new Monroe sensitrac shocks and struts. Any experiences or advice? I would very much appreciate any help. Thank you.