adrial

The gas charge is there only to prevent cavitation of the fluid in the Damper ... you want to run as little gas charge as possible, while avoiding cavitation (evident by chatter in the Force-Velocity curve, if you put them on a shock dyno).

AudiOn19s

All good points, I"ve run Nelson Ledges (extremely bumpy) with this canister pressure and almost the same settings that I ran with at Mid Ohio and I don't feel like the car acts negatively over bumps at all, nor really sliding the tires THAT much anywhere, I do use Nitto's which require a good bit of slip angle so I do tend to drive that way.

His suggestion is just that I'm giving up a little bit of overall grip by running the shocks soo stiff. I guess no harm in testing based on the other comments here, I may just have to exeriment and figure out if I like the change or not.

Matt Romanowski

We need to clarify a little. Are the springs too stiff of is the dampening of the shocks too stiff? Tune the "stiffness" of the car with springs and the dampening of the springs (and weight transfer) with the shocks.

AudiOn19s

I probably should have asked more questions while I had him yesterday instead of here, I was simply trying to understand if it's going to change the way the shock works by lowering pressures which you've already answered. It's basically only going to act like taking away a little spring all around if I lower all the corners the same amount. Others have also stated it's best to run the lowest pressure you can without the fluid cavitating which also backs up my shock guy's statements to a degree that he feels my pressures are too hight.

I don't think that the car is too stiff in either spring or shock side. I don't think the shock has issues controlling the spring esp based on my experience at the ultra-bumpy Nelson Ledges. His suggestion was simply his preference to see canister pressures lower based on his past tuning experience with these shocks and professional race teams...and the fact that I had all sorts of balled up rubber all over the shocks which he felt could be a sign of sliding the tires too much.

I will openly admit that while I really try to understand suspension tuning alot of the time I'd make *** backwards adjustments without Carol smith's book in my tool kit

Andy

JoeMag

...have a question here. Some folks are talking a spring rate of shocks (force vs displacement) and other are just talking force (X psi pressure = lbs force).

Is there an estimation out there based on appx size of cannister to what the "spring rate" is of a shcok and how it changes with pressure change? For example, if you have a shock with a VERY large cannister (unrealistic size) it would not have much change in force vs movement of shaft because volume of oil movement wouldn't effect volume of gas much -- you would just have shock that "pushes up" with the same force as it's compressed.

My shocks (pro trak) just publishes force vs cannister pressure.

Matt Romanowski

If I understand what your asking - the canister size has nothing to do with the force provided from the gas pressure. The force is a result of the shock shaft displacing oil volume, hence the force is linked to the shaft size. I think Geoffrey posted what Moton says the rate is for each of their shaft sizes.

kurt M

As the oil is displaced by the shaft the oil compresses the N2 into a smaller volume and the pressure goes up. A progressive spring of sorts. the smaller the volume of gas being compressed (other factors being the same) the higher the progression. The number does not change but to some extent large or small the gas pressure does.

JoeMag

Had the car up on jack stands with wheels off on Sunday, so figured I’d try and answer this question about spring rate.

I attached shock pressure gauge to shock and moved shock up and down and monitored how shock pressure changed vs shock compression. Then using graph that came with my shocks, I converted shock pressure to lifting force of shock. Below is graph of shock force vs compression with a regression showing formula for the line. In this range, linear fits well. The interesting thing is that the spring rate (lbs per inch) of the shock is quite low, being the 4.76 lbs / inch (slope of line). Technique seem reasonable?