Robert K
06-21-2007, 01:05 PM
Thought I'd post a followup to my post a few weeks ago about why E34 rearends seem loose. As a refresher, I took the rear controls arms off of my 1991 535i with the intentions of replacing the control arm bushings, the differential bushings, and the rear subframe mount bushing. To make a long story short, I really didn't feel there was anything wrong with the original bushings, so I put it all back together with the original bushings.
Immediately after that, I ordered a set of Bruno's subframe bushing inserts. These are essentially hard nylon washers that fit between the subframe bushings and the small plate that bolts to the bottom of the bolt that goes through the subframe bushings. Installing the inserts made a BIG difference. The car now seemed to respond to steering inputs as a whole. The rear end no longer felt like it was about a half step behind the front. I just got done putting new tie rod ends on the front end and having it aligned. Between the new tie rod ends and Bruno's inserts, my car really feels renewed. But I think the biggest difference came from the inserts.
BMW designed the subframe bushings to isolate the rear suspension from the chassis to provide a smooth ride. But I think they overdid the size of the bushings. The result is that the subframe can squirm around TOO much. Bruno's inserts limit the amount of travel the subframe can squirm around, thereby greatly improving the responsiveness of the rear end. However, I did pick up a bit of extra noise when the rear wheels encounter bumps, so I think a hard rubber or urethane would probably be a better material than the nylon-type material that Bruno uses. Those materials would still limit the movement of the subframe but still provide some isolation. I am going to be on the lookout for these materials and will make a set for myself to compare against Bruno's nylon ones. I've also read on this forum of persons filling new subframe bushings with some type of hard plastic or urethane before installing their new bushings. I also think that might be an excellent solution towards restricting the movement of the subframe.
So, there's what I've learned from this journey towards tightening up the rear end of my E34. I am so much happier with the way the car handles now. I hope this helps others out there who have similar problems.
Grace and peace,
Robert K
1991 535i
Immediately after that, I ordered a set of Bruno's subframe bushing inserts. These are essentially hard nylon washers that fit between the subframe bushings and the small plate that bolts to the bottom of the bolt that goes through the subframe bushings. Installing the inserts made a BIG difference. The car now seemed to respond to steering inputs as a whole. The rear end no longer felt like it was about a half step behind the front. I just got done putting new tie rod ends on the front end and having it aligned. Between the new tie rod ends and Bruno's inserts, my car really feels renewed. But I think the biggest difference came from the inserts.
BMW designed the subframe bushings to isolate the rear suspension from the chassis to provide a smooth ride. But I think they overdid the size of the bushings. The result is that the subframe can squirm around TOO much. Bruno's inserts limit the amount of travel the subframe can squirm around, thereby greatly improving the responsiveness of the rear end. However, I did pick up a bit of extra noise when the rear wheels encounter bumps, so I think a hard rubber or urethane would probably be a better material than the nylon-type material that Bruno uses. Those materials would still limit the movement of the subframe but still provide some isolation. I am going to be on the lookout for these materials and will make a set for myself to compare against Bruno's nylon ones. I've also read on this forum of persons filling new subframe bushings with some type of hard plastic or urethane before installing their new bushings. I also think that might be an excellent solution towards restricting the movement of the subframe.
So, there's what I've learned from this journey towards tightening up the rear end of my E34. I am so much happier with the way the car handles now. I hope this helps others out there who have similar problems.
Grace and peace,
Robert K
1991 535i