According
to Roland at H&R the spring rates for the "Street" coil-over setup
are 270-375 lbs/in front and 340-400 lbs/in rear. Of course the fact
that the rear springs are mounted inboard of the wheels means that the
actual wheel rate at the rear is less than the spring rate. The front
and rear springs are progressive due to the fact that as they compress,
some of the coils will touch (bind) and gradually reduce the number of
active coils. Furthermore, as the front suspension compresses the
bump stops come into play which raises the rate a bit if you really work
the car.
I asked Roland about possible choices
for going a bit stiffer. He said that on the front I could go with
E36 M3 springs which can be had in either 315 lbs/in (37% stiffer) or 340
lbs/in (48% stiffer). For the rear I could move up to "Group
G" Race springs. These start at 570 lbs/in which is 68% stiffer than
the baseline setup. Roland felt that the baseline damper valving
would still be appropriate for these higher spring rates. I would
have to try that for myself I suppose, but Roland knows more about dampers
than I ever will.
Comparison of Spring Rates
Spring Type
|
Front Rate (lbs/in)
|
Rear Rate (lbs/in)
|
E30 M3 Stock
|
?
|
?
|
H&R Sport
|
185
|
380
|
H&R Coil Over
|
270-375
|
340-400
|
H&R Race
|
315
|
570-680
|
Eibach Race
|
160
|
455
|
Roland offered that the H&R Sport
Coil Over baseline spring rates are not particularly stiff. But he
claims that most people like the setup this way. In fact, he said
that many people who end up trying stiffer springs eventually return to
the baseline springs. I must admit, the ride is incredibly well controlled
considering how comfortable it is. The package is definitely well
engineered. The car will understeer through slow tight corners, but
is beautifully neutral through fast sweepers and will go a little loose
under certain conditions (cold tires!). I run about 3° negative
camber all around right now. The K-Mac (TMS) front camber plates
are set full negative up front. The rear gained some negative camber
with the lowering of the H&R kit. I have some K-Mac rear camber/toe
bushings. Once I install them I hope to reduce the rear camber to
about -2.5° which should reduce understeer a bit more as well as improve
traction under acceleration. Even so, tire temperatures are quite
even accross the tread both front and back with 225-50-15 Kumho's on 15"x7"
OT20 wheels.
In terms of ride height, the rear was
lowered about 0.5-0.75 inches. I did not measure it exactly.
The front is adjustable of course. I have the perches set about 30%
down from the highest point. This still lowered the front quite a
bit. Probably a little over 1.5". I think that I will raise
the front a bit in the near future as I do not want to overly disturb the
front suspension geometry and induce bad camber curves, additional roll
couple and possibly additional bump-steer.
All in all I would highly recommend
the H&R coil over kit. It is very well made and performs exceptionally.
Also, the customer service provided by Roland at the U.S. H&R headquarters
is second to none. Now if only the dampers were adjustable 8^)
|