Shock Question

[RJ16]

Hi,
I'm looking for some information on how changing the Nitrogen psi in the shocks affect the cars handling. I haven't been able to find much information on this subject; any help would be greatly appreciated.

[save the racers]

125lbs in the shock is around 25lbs of spring rate.It is the same at all travels where a spring would be 500 at the first 1'' ,1000# AT 2"" ,1500 at 3".The l/r is where you might go to 300lbs to calm it down when you come off the bars.If you fill the shock at full extension then compress it the pressure will be higher.Years ago when gas shocks first came out most people didn't know anything about digressive pistons, low speed ,velocity ,lbs at 6" of travel etc... Gas pressure was incorrectly blamed for the extra control that the better shocks gave.

[stock car driver]

125lbs in the shock is around 25lbs of spring rate.It is the same at all travels where a spring would be 500 at the first 1'' ,1000# AT 2"" ,1500 at 3".The l/r is where you might go to 300lbs to calm it down when you come off the bars.If you fill the shock at full extension then compress it the pressure will be higher.Years ago when gas shocks first came out most people didn't know anything about digressive pistons, low speed ,velocity ,lbs at 6" of travel etc... Gas pressure was incorrectly blamed for the extra control that the better shocks gave.

Maybe Im not understating this, but I know I have gas shocks with more than 125 psi in them and they do not ADD any spring rate on scales on my car. The only shock I have that add to a corner when hooked up on the car on the scales is the lr.

[zeroracing]

Gas shocks give a spring rate, its not huge but it is some, this is basically the gas pressure force on the end of the shaft itself. Depending on the car and shocks, it may or may not show up much on scales. It also will vary some with the position of the shock, further out less rate, further in more rate. Shocks with base valves may not have much of it.

Many drivers complain when the gas pressure is too high they have a feeling of being on top of the race track (in slick). This is much of why base valve shocks became popular. It comes down to a pneumatic spring does not react like we are accustomed to. Motocross guys have been using pneumatic pressure in place of rear springs on some supercross stuff and some riders complain of the same feeling. Ryan dungy fell a few times and I remember his remark was lack of rear feel/grip.

You put more gas Psi on rough or heavy for couple reasons. Most notably is that is keeps the shock from cavitating. You see a higher shaft velocity when your hitting holes and throwing the car around, causing more pressure drop across the piston during compression, thus the need for more PSI to keep cavitation from happening.

I will agree with save the racers that gas pressure is often blamed when other parts are miss understood. For the most part on dirt you want the minimum amount of gas pressure that will ensure you do not have cavitation. With the LR being an exception, in that you can use high pressure to help get on the bars.

[Racer96m]

For the most part on dirt you want the minimum amount of gas pressure that will ensure you do not have cavitation.

Thats it in a nut shell. Press will very depending on how the shock is built and you can up the press slightly for a rougher track to help with cavitation, but even the LR's are coming down in press these days compared to what they were. You dont up pressure to jack weight, thats what the spring is for, shocks are just for timing. My .02

Dave

[RJ16]

Thanks for the information, was a big help with understanding the purpose of changing the psi and how it effects the car.