Penske shocks

[Jay Jacobellis]

I have 7500 series shocks on the front of the Vector I just bought does anyone have a starting point for how much nitrogen pressure I should start with

[Diamond Level Motorsports]

The manual doesn't spec a pressure. I would guess 100 lbs as a starting point although I personally would use less. Additionally, I use compressed air, not nitrogen. I know people will disagree with that but my sources say it doesn't matter that much.

[winsmith]

Penske says 100 psi or pressure as required by track. I have never run 100 in anything, but have run low as 30 and as high as 80. And that is in everything from a FST up to a 3000 lb stock car. The pressure just adds stiffness or spring rate. I would start at 50. That is what works for us, I am sure others will have different opinions.

[S Lathrop]

The correct pressure can only be determined by a little shock dyno testing.

What you need to do is figure out what the maximum velocity the shock is likely to see on the front of a FST or the rear. Then on the dyno you simply stroke the shock at that velocity and listen for when the shock starts cavitation.

The same shock on say a FF would require a minimum of 150 psi.

If you operate the shock at velocities that cause cavitation, the shock becomes ineffective. It no longer dampens suspension movement.

The friction in a VW front suspension, under loads, gives a lot of dampening, so the shocks are not that critical if they are slightly under pressurized.

[t walgamuth]

What should they be on a 98 van dieman used for autocross?