[s-cars] Suspension/steering stiffness question

[Taka Mizutani]

Ivan-
comments inserted within:

On 4/8/06, Ivan Demkovitch <idemkovitch at yahoo.com> wrote:
>
> List,
>
> I'm about ready to overhaul suspension on my 93' UrS4
>
> Currently car has 133k miles and PO installed Bilstein SP + H&R at around
> 75k.
> My feeling is that shocks already done. Also, I don't like current
> stiffness.
>
> 1. To me it's too harsh and I don't see this benefiting handling. It
> almost feels like wheels disconnect from the pavement on a
> bumpy road when I go into tight turns.
>
> However, I like ride height and hate to raise a car since it will look
> silly with my 17" RS4 style wheels.
>
> So... What do you suggest for suspension components? I like firm but soft
> ride. Not too much body roll but without go kart feeling.
> Different springs? Shocks?


I think you're experiencing a few things here:
1. Bilstein Sport and H&R spring combinations are not properly matched- the
Bilsteins should ideally be revalved for the H&R springs. I believe this
hypothesis to be correct due to my direct observations that the Eibach
(lower spring rate)/ Bilstein Sport combo works very well- the damping is
nearly spot-on for the spring rate.

2. The 17" wheels you mention may be significantly heavier than your stock
wheels- increased wheel/tire weight results in increased unsprung weight,
which will cause ride quality to suffer. If you can, find someone to borrow
some lightweight wheels & tires and see how that impacts your ride quality-
I'll bet that ride quality will be improved if you reduce the weight of your
wheel/tire combo. Easiest way to validate this (if you don't have big
brakes) is to borrow a set of the 15" forged BBS (15x7.5" ET 35) from a '91
200q or '90-94 V8q- if the suspension seems to work much better due to the
15 lb. wheels and lighter tires (less crashing over bumps- the taller
sidewall height will soften up the overall ride), then the heavier
wheels/tires are not helping your goal.

Personally, I think even the Bilstein/H&R combo is not stiff enough in roll
stiffness, I'd definitely pull the shocks and have them rebuilt and revalved
to spec through either the CT or CA offices of Bilstein USA.

I would also replace the steering damper- if you use the Fox part, it's
really cheap and will help reduce steering kickback over bumps.

I will leave the other suspension diagnosis to others who are much more
qualified to answer. :-)

Taka