Along with the Koni dampers I installed Ground Control rear shock mounts. The BMW rear shock
mounts are a known failure item. Be it the standard E30 units, the 325iC convertible mounts
or even units from the E36 (which happen to fit the E30 chassis), they all have a limited
life span. The Ground Control rear mounts are machined from billet aluminum, but also employ
a pair of poly-urethane bushings, both to allow for the small angle change which occurs as
the rear suspension moves through its range of motion, and to give some amount of compliance.
Depending on the way you insert the poly bushings, you can get a variation in the stiffness
of the mount. You insert them one way for street, or flip them over for race conditions.
I installed them in the "race" position and do not find them at all harsh. The car feels real
"buttoned up" with these mounts installed. Plus, they should last forever, so even though
they are more expensive starting out, in the long run I believe it will be money saved.
Although I had been previously using K-Mac camber/caster plates with the H&R's,
when I installed the Ground Control suspension
I switched to the Ground Control camber/caster plates. Unlike the K-Mac's, the GC's are a full race design. They
do no employ any poly-urethane but instead mount the strut to the chassis through a solid spherical bearing. Since
I had used similar racing plates on my Rabbit as a daily driver, I was not concerned about them being too stiff.
In fact, as long as you ensure that you have the proper amount of free travel in your suspension to match your ride
height and springs rates, then I feel solid mounting the suspension to the car is perfectly streetable. You
do get an increase in "noise" but to me it is worth the incredibly precise feeling you get through the seat
of your pants. Not to mention a reduction in unwanted suspension compliance.
I was very impressed with the fit and finish of the Ground Control plates. They are well made and well engineered.
The upper spring perch is of a "spherical cup" design, which allows the perch to compensate for slight misalignments
in the spring as it compresses. Also, the upper perch rides on a thrust bearing to allow the lower strut to
rotate (when you steer) without binding up the spring. I drove my Rabbit for a while without thrust bearings
in the camber plates and the springs would constantly bind up when making tight turns - no fun.
But best of all is that the Ground Control camber/caster plates are designed with a very short "stack height".
This gives one the maximum amount of front suspension travel, about an inch more than the K-Macs with the car
set at the same ride height. An explanation follows on page 3...