I noticed that palmerwnd has urethane bushings on his Q. I want to move to these also but don't know where to start or how difficult it would be to perform the change over. Also, is there a preferred supplier for these bushinges?

Might want to check with Q45tech on his experiences with same. It was posted on the old board, so maybe the monarch can bring it up as an article. Seems like it caused him to change the rear subframe when they were used with a Stillen 24mm rear bar.

Hopefully he will be kind enough to chime in again. Following is quote from the previous board:

The safe [dry] rule of thumb is never install a rear sway bar equal to or > the rear spring stiffness: and a 20 mm bar is only 34% of spring if perfectly coupled with solid metal bushings...the more typical rubber oem bushings slack will reduce the 1st inch [of wheel/body travel] to almost no added stiffness.....then the bar will kick in progressively. So under a fully side to side swing [-3 to zero to +3] the 20 mm might get close to 85/366 or 23% total stiffness increase. {ON A GOOD DAY}

I use urethane rear bushings and rigid metal inserts to try to get the full 34% usually bend/deform the end links as they are not designed to take the full load [rubber bushings remember -sideslip].

The severe problem is no shock absorber design takes into account the extra springiness of a sway bar even the Tokico blues are only 10-15% stiffer not the 34% extra rebound one needs in auto cross or a 70 mph emergency lane change.We have about 7 Q customers with the solid 24 mm rear bar, many for over 5 years guess they just learned to drive better no accidents I am aware of!

I had the 24 mm for 4.5 years before down grading to the 20 mm to make my bottom and hernia feel better on railroad tracks! Miss it on some ocassions but I've learned to adapt to another 0.9" of sway.

Oh! I started out with urethane till I bent two sets of end links [the heavy duty ones supplied with bar]. Then I tried various combinations of rubber/urethane finally all rubber. The problem is the 4:1 reduction 1" of wheel movement is only 1/4" of movement at the end link......very very hard to make a fine adjustment that stays the way you want it.....what happens is nothing then wham a sudden stiffening which will cause a lack of smoothness and snap oversteer with rubber bushings. Severe oscillations when you whipsaw the steering again due to the imability of shocks to provide adequate control over something twice as stiff as they were designed for!!!!!!!!!

By the way some of my driving bent the bar an 3/4" permanently part of the reason why the rear subframe needed replacement

Might look at http://www.energysuspension.com/prod1.html

BMW are notorious for bending /breaking off sway bar mounts after an upgrade. The manufacture only need worry about what they install.Since the 20 mm rear bar was a factory piece [on the Active car] and the factory end link is used and the rubber bushings were added to soften the initial impact . I would expect that the stock piece can handle the full 40 x4 =160 pounds that might be exterted against it obviously the non factory end link for the 24 mm solid bar wasn't strong enough for 500 - 600 pounds with urethane bushings.

The rear subframe has 4 silicone filled isolation bushings [which leak with a rear end collision [later not right away]. The only thing about the rear suspension that is not attached to the subframe is the top of the shocks which mount to the body. So there is some side to side sway as the subframe moves 0.5".

Urethane is aways fun if you can stand the impact harshness!