Firstfives.org

Bilstein HD's and Sport rear shocks have circlip grooves in the tubes, used to hold the lower spring perch plate.

Correct me if I'm wrong : choosing the lowest groove allows the car to sit lowest. Fine as long as when the shock is fully extended the (lowering) spring remains compressed enough to stay in position in the perch notches.

Not sure about the physics, compression stresses, limits after that. Mounting instructions are in five languages, mostly saying have them professionally installed.

The HD shocks come with two sets of perch plates. One is a relatively flat disc that uses the stock rubber perch (notched) gaskets, the other set looks more like an inverted bowl, notched, that allows the spring to sit an inch lower on the shock.

Reckless experimenters could cut their stock springs, use the notched plates and report results here.

I used the flat perch plate in the upper groove as the spring would come loose when useing the lower groove. I really like how it is now as I have an extra 90 liters fuel tank in the back so it's already pretty low due to weight. I needed to roll the inner fenders as they would almost continuesly rub. They still look stock from the outside but I've al the clearance I need now.

Assembled one unit on the bench. Looks like my perch pick requires spring compression, a half inch to tight. My imagination doesn't see the lower suspension arm able to PULL down, at least enough to let the (rear) spring get loose, rotate on the notched perch rubber.

He said, looking back at the rear suspension parts scattered all over the freeway.

My hand is up as one of the "reckless". I played around cutting the springs on the wife's e21 until I got a good height and stiffness. I had three sets to play with though and a car that was only driven on weekends. To avoid the need to keep the lowered spring in contact with the perches, you just cable-tie the coil to the perch. Best to use two ties on each side. They only do any work when you jack the car up anyway (unless you get some wheels in the air around the corners of course!).

Once you have the height right, you can either go with keeper/helper springs or Bilstein will shorten the damper stroke for a significant fee. You can (of course) just keep using the cable ties like me. You can also cut down the rod yourself, but I've heard Bilsteins have a certain location in the stroke you are supposed to maintain.

Cheers

Pete K wrote: They only do any work when you jack the car up anyway (unless you get some wheels in the air around the corners of course!).

This happens quite often. Atleast more often then you think.

Besides why not buy the B8 shorter ones?