911T to Kremer ST -questions - suspension

[Flunder]

Hello Raj: I have the same shocks that I had intended to use on the 71S project car. However, note that the part number 8210-1046 SP decodes to KONI externally adjustable rear shock for 911 and 912 for MY 69 to 74 (and later I suppose, as my catalog is dated 1974). As you mention, it appears similar to the 8211-1119 KONI for use on the rear of 914-4 and 914-6 with KONI springs or Ginther springs. The pair of shocks that i have are also stamped 8210-1046 SP but are dated 2 71 and are painted KONI orange and have the winged KONI decals on them. Nice vintage race part for ST!

[Flunder]

...any ideas why the factory went to bilsteins when they had adjustable with koni and they had experience with it

Raj: As i have been told, once the focus for the competition oriented 911 switched from rallys to circuit racing, the teams started to lower the circuit prepped cars more radically and it turned out the KONI shocks had insufficient piston travel at the lower ride heights and hence lost functionality. The de Carbon gas charged technology used by Bilstein did not have similar issues with piston travel and were better suited to lower ride heights. Perhaps Flieger can chime in as Max seems to have a keen understanding of chassis dynamics and theory.

[Flieger]

I'm flattered.

But, I do not really have a good answer to the question of why the factory switched to Bilstein. Perhaps just a sponsorship deal? Or the fact that Bilstein spindles are easier to raise/can be raised more than KONI struts? They might have wanted Bilstein struts and then decided to go with Bilstein rear dampers to keep their supplier Bilstein happy.

The gas-charged single tube design is better to prevent oil frothing and would hold up under fast piston velocities and repeated cycling better than the twin tube hydraulic design of the KONI. However, if they were sufficient for rally use, KONI should be more than up to circuit use due to the lesser suspension travel.

The gas chamber to pressurize the main fluid chamber is located in-line with the fluid chamber so I would think that the gas-charged design would have less piston travel compared to an "equal" twin-tube hydraulic design- i.e. one that would fit in the same strut housing or on the back of a 911.

Interestingly, my car has raised rear damper towers and a cross-brace between them. I am running Bilstein yellows. I believe that means Sports. The dampers were put on many years ago before I got into suspension details. Perhaps this was done to accomodate the Bilsteins?