The picture above shows the difference in front suspension travel offered by the Ground Control camber/caster
plate vs. the K-Mac brand. Assuming you do not shorten your struts or re-locate your spindles, then
front suspension free-travel is entirely governed by the distance from the bottom
of the bump stop to the top of the strut bearing (or camber plate). I call this the "stack height" and it is
the distance between the purple lines in the picture. Note that the stack height for the Ground Control
camber plate is quite a bit shorter than that for the K-Mac camber plate. On the K-Mac, it is impossible
to see the bump stop since it is down at the bottom of the strut. The H&R system uses the Bilstein
"upside down" approach where what appears to be the shaft of the damper is actually the body.
In any case, the H&R bump stop is roughly the same height as the cut down Koni bump stop shown on the right,
which allows an apples-to-apples comparison.
Note that there is some suspension travel available after the strut housing contacts the bump stop. But at
this point your effective spring rate rises quite rapidly, so the amount of extra travel is rather limited.
The way I have my suspension set up, with stiff springs and cut down bump stops, the majority of conditions
have the suspension in the free travel regime, with the bump stop only used as an emergency to cushion the blow
of an unusually large bump. On the left of the picture, note the distance between the top of the strut housing
and the bottom of the bump stop. Now consider that the suspension is unloaded in the picture. With 450 lb/in
springs and about 700 lbs on each front strut the suspension will compress quite a bit leaving only about
half the visible amount of travel available in compression from static ride height. Now imagine what happens
when using the K-Macs. There will not be much room for free travel if you set the car at the same
ride height. I should point out that the tall stack height shown
on the K-Mac setup is partially caused by the rather tall design of the H&R upper spring perch. One should also
keep in mind that the K-Mac upper strut bearings are only slightly taller than the BMW factory units
(about 3/32" taller). Thus with factory strut bearings on a lowered car you will also run into this problem
of reduced suspension free-travel.
for more information about suspension travel.