[BiturboS4] suspension upgrade

Chip Goetzinger chip at auguricorp.com
Mon Sep 9 14:59:31 EDT 2002

<<2) I'll pose a question: can we agree that, theoretically, a well matched
H&R-spring/Bilstein-damper setup would handle identically to a H&R coilover
setup w/the same specs, and would cost the consumer less? If so, great. If
not, why?>>

I think "identical" is where you'll run into issues.  Disclaimer first - I
have more experience with Mustang suspensions than S4 (they need more work
;oD), so if I've made assumptions that don't apply to the S4, let me know.
One thing that I can think of is a difference in unsprung weight.  Different
location of the springs (closer to the control arm pivot for standard,
farther for coilover) means that the coilover springs can be smaller and
lighter while achieving the same wheel ratio.  In other words, for the same
wheel rate (most would say, incorrectly, "spring rate") the coilover spring
will be smaller and weigh less - reducing sprung and unsprung weight.  This
can be significant or minimal depending on how far inboard the stock spring
location is compared to the damper.

The second difference is going to be for track geeks only -
corner-weighting.  Adjustable-height coilovers mean you can corner-weight a
car for best handling - something you can't do with regular springs/shocks.

However, on a street car, neither of these things will be all that
noticeable, which is why in your case I'd say "practically identical", not

One other point is that you say for a "well-matched" system.  Another point
typically in favor of coilovers is the availability of springs in 25#
increments, and the ease of changing them out - which means easy tuning, and
even relative ease of using one rate for the track, one for the street (this
is assuming adjustable dampers as well).  Is this the case for the S4
systems available?

</Pedantic mode>  ;o)

'96 Mustang Cobra Convertible - 435 RWHP (Laser Red, Saddle, Saddle - shhh,
it's sleeping)
'02 Audi S4 6-speed (Santorin/Onyx/Silver Alcantara sport)
'02 Nissan Xterra XE-SC 4x4 AT (Black)

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