Does Ambient temperature affect gas shocks?

[Roland Kunz]

Hello

As long you drive forward the heat will blow away

More risky is when the shocks shuffle on the heatexchangers.

Grüsse

[autobonrun]

I have not received a response from Bilstein, Germany, but I did have a long phone conversation with Bilstein, USA. The answers to the questions I asked earlier are posted below. If I ever get an email response from Bilstein Germany that disagrees with any of the answers, I'll post it.



1) Is the purpose of the gas fill only to prevent foaming of the hydraulic fluid or does it actively contribute to the damping; if so in both directions of travel?

+ The function of the gas is to prevent cavitation (foaming) of the hydraulic fluid as it flows through the internal valving. Basically, the gas keeps the fluid above it's vapor pressure even if the temperature increases. There is a minor side benefit of aiding the hydraulic fluid return the shock to its extended position although this is not its primary function.

2) How does Bilstein compensate for changes in shock temperature (either from ambient conditions or racing) such that the performance is consistent? I would think the gas pressure would change with temperature.


+ Temperature has only a minor impact on the gas volume and pressure because the gas only occupies a small portion of the shock. Basically the gas fills only a 1" to 2" section of the cylinder. Also, over the temperature range in question, Nitrogen does not exhibit a significant change in volume/pressure.

3) Are Bilsteins more stiff than say Koni's or Boge's because of the gas charge or because of some other internal design.

+ The firmness of the Bilsteen shock is a function of the internal design, not the gas charge. Primarily, the firmness is controlled by the internal valving. Bilstein stated that their purpose was not to provide a stiff shock but one that is firm yet still comfortable.

4) Is there a quantified percent difference in stiffness between the Bilstein HDs and the Sport Shocks.

+ It is estimated that the Sport Shock is only about 15% more firm than the HD Shock.


5) Lastly, is there a Bilstein recommended setup for Porsche 911's (eg. HD front, Sport Rear).

+ Bilstein recommended going with the same type shock all around. However, they do recommend that the Sport Shock be used on cars that are lowered and the HD shock be used on non-lowered cars. The Sport Shock is about 1" shorter than the HD shock.