In a message dated 1/14/02 10:55:20 PM Central Standard Time,
solo2inseattle@hotmail.com writes:
> I do not believe that the high dollar shocks will make as much of an impact
> in the non-stock classes. One of the larger benefits of the high pressure
> monotube shocks comes from the ability to use their nitrogen preload to
> supplement spring rate and the ability to use their stiffness to reduce the
> reliance upon springs. In STS and SP you can already have the high spring
> rates. Just my $.02.
Actually, most people in Stock are doing the opposite; they are running
lower pressure. Pressure is just one factor, you also have to consider shaft
diameter. Simply put:
gas pressure extension force = gas pressure x shaft area
The pressure is always trying to escape the body, this why the shaft on
pressurized shocks always trys to fully extend, the pressure working on the
shaft diameter creates the net extension force. On a double tube shock,
converting from gas to hydraulic eliminates this force, though due to most of
them being low pressure the net effect is small. Most aftermarket shocks
utilize a larger diameter shaft to both accomodate the valving adjuster
running down the center and have sufficient strength as a result. If you did
not reduce gas pressure to account for the change in shaft diameter, the
extension force would be greater than OE at the same pressure. However, the
extension force is not like a spring, whose load force increases in magnitude
with distance traveled. The extension gas force is for the most part a
constant preload, nothing more, and the overall magnitude is not really that
great in general. Again it just depends, some of the custom shocks have
considerably larger shaft diameters than OE and the effect becomes more
pronounced.
As for running extremely low gas pressure forces, if you talk to the tech
people at Koni they will disagree heavily with this. In fact, KONI NA
seriously frowns on running less than their minimum recommended monotube
pressure of 320 psig, though some other manufacturers tout it. Koni also
does not believe in using remote reservoirs for technical performance
reasons. In short, they believe a remote reservoir shock is inferior to a
non-reservoir shock, but please don't try to drag me into that argument, I
have no idea, it just conflicts with some other opinions and perceptions.
They also refuse to install schraeder valves, siting them as a major leak
source. I have managed to try some different pressures on my Z06 28's and
frankly I cannot tell any real differences, though my shaft sizes are not
that much larger than OE and this may negate those factors. Since their
seals are designed to use the pressure as a sealing force, they also have
internal seal leakage concerns when using lower pressures. If the gas
pressure escapes into the oil, the dampner will pretty much fail. Some
people have run monotube shocks with no gas pressure, basically it will jack
down onto the bumpstops under a variety of conditions and more or less not
function as a dampner, less than ideal IMO.
Mark Sipe
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