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Re: <E34> Bilstein vs Koni

Dennis Ignacio (E34 535) with Dinan Stage I shocks and springs is
concerned about ride comfort and asks for advice on Bilstein vs Koni:

>I ended up taking the car back to Dinan...
>Guess who asks for the keys, Steve Dinan himself. After 
>he gets back, he claims that they are riding as designed...
>My salesman offered to replace the fronts with Konis which are 
>adjustable. They happen to cost more and I have to pay the for 
>the installation... 
>should I wait for the current (Bilstein) setup to break in, 
>OR should I spend more to get the Konis put on the front?

Dennis,

First of all, if you are dealing directly with Dinan, I think you are 
in good hands.  Their salespeople I've spoken with (Jeff Hecox and 
Michael Boyle) are quite knowledgeable.  When I've had questions 
they couldn't answer, they have always allowed me to speak with their
engineers instead of trying to BS me.

I don't think you can go wrong with Koni or Bilstein shocks.  They 
are both high quality products.  However, I'd recommend you stick 
with the Bilsteins.  They are already installed on your car and cost 
less.  I also think the Bilstein design is technically better 
(except for Koni rebound dampening adjustment).

Part of this is personal bias.  I made several calls to both Koni 
and Bilstein to figure out the advantages of each.  The Bilstein tech
rep (Cleve Hardaker) was very helpful -- much more so than the 
person at Koni (maybe it was just a bad day to call).

Technically the main difference is that Bilstein uses a monotube 
(single tube) gas shock versus the Koni twin tube (inner and outer
tube) gas shock.  In the monotube design, the nitrogen gas 
and shock fluid are separated.  The gas pressure is higher and the 
shock piston is also larger diameter.   These features make the shock 
more sensitive, more cavitation resistant, and aid cooling.  

Except for sensitivity, at street speeds, these differences probably 
don't amount to much -- I'm probably not a sensitive enough driver to 
tell the difference. 

Koni's advantage is its adjustability.  The front strut is 
especially nice.  Just pop the hood and twist the top of the 
strut.  The rear shocks are also adjustable, but it's way too hard.  
The shock has to be removed from the car (remove spring, push shock 
rod down all the way and turn to adjust).   

Adjustability sounds great (and is, if you like to experiment), 
but Koni street shocks only have adjustable rebound dampening 
(wheel traveling back down after bump).  The compression (wheel 
traveling up) is not adjustable.  Even though rebound can be 
adjusted, compression dampening affects ride comfort quite a bit.  
I doubt the Koni is any softer in compression than the Bilstein.  

Tires also make a big difference in ride comfort.  When I change 
to my stiff BFG R1 track tires (same size as stock 225/50-16), 
the ride is much harsher.  An all season radial, the same size, 
is usually much less stiff than a performance tire.  If you still 
have your original tires and wheels, you may want to reinstall 
them until the shocks break-in.

My Bilstein sports felt much better in 300-400 miles and the 
ride compliance continued to improve for about 2,000 miles.

 Regards,
    
 Pete Read
 '88 M5