Penske Shock Help/Rebuild

[Numbskull XIV]

Hello guys,

The car is a RF97 Van Diemen FC.

I have been reading up on shocks/springs and have a few questions on rebuilding them. I searched the apex archieves and got a few answers. What are some "do's" and "don'ts" of the job? I'm not looking to re-engineer the internals with different jets or needles, just thoroughly clean up what I have, replace the o-rings, replace the oil (5w Penske oil or "yellow" oil from Pegasus), and reset all the settings back to a solid baseline.

1- First off, I know that they are triple-adjustable Penske's but what exact model shocks do I have? old style 8760's? 8765's?

2-What are the 3 "shim-looking" rings between the spring retainer and the spring on one end of each of the shocks? What do they do? control suspension droop? bump steer? ride height?

3-What is a good baseline for front and rear? I have a Primus racing baseline guidebook for the "97 road course" that came with the car which suggests the following for Goodyear tires:

-FRONT-
SPRING RATE: 400lbs
SPRING PRELOAD: 6 turns from contact
RIDE HEIGHT: 28mm-34mm
PENSKE DAMPER VALVING PISTON: Linear 2 degrees bump/linear 1 degree rebound with 0.040 bleed (I'm not sure what this means)
SHIM STACKS: A-bump/d+rebound (I'm not sure what this means)
CANISTER PRESSURE: 200lbs
DAMPER SETTINGS: HIGH SPEED BUMP-6 off full hard/LOW SPEED BUMP-10 off full hard/REBOUND-7 off full hard

-REAR-
SPRING RATE: 650lbs
SPRING PRELOAD: 1 turn from contact
RIDE HEIGHT: 36mm-42mm
PENSKE DAMPER VALVING PISTON: 2 degree bump/digressive rebound 0.012 preload with 0.040 bleed (I'm not sure what this means)
SHIM STACKS: A-bump/E rebound (I'm not sure what this means)
CANISTER PRESSURE: 200lbs
DAMPER SETTINGS: HIGH SPEED BUMP-5 off full hard/LOW SPEED BUMP-10 off full hard/REBOUND-4 off full hard

-CHASSIS RAKE: 6mm-9mm


What do you guys think of this baseline? Outdated? Suggestions? Changes?


Thank you guys for the help,
Jon Updegrove
jonupdegroveracing@gmail.com
610-509-7321

[R. Pare]

Hello guys,


1- First off, I know that they are triple-adjustable Penske's but what exact model shocks do I have? old style 8760's? 8765's?

2- What are the 3 "shim-looking" rings between the spring retainer and the spring on one end of each of the shocks? What do they do? control suspension droop? bump steer? ride height?

1 - Early 8760's I believe is the correct model number.

2 - Torrington needle roller bearing in the center, with a Torrington thrust washer either side. They allow the endcoil of the spring to rotate as the spring is compressed and released - a normal things with coil springs. Helps reduce friction.

[S Lathrop]

The shocks are 8760. They are early versions but are still a good choice.

The bleed is simply a .040 diameter hole in the pistons that allow oil to by pass the shim stank on the piston. The other information is details of what shim stack is on each side of the piston. Go to the Penske website and they will have information what the coding for the valve stacks are all about.

The 2 degree bump refers to an angle cut on the surface of the piston where the shim stack seats. The higher the angle the more force it takes to open the stack and allow oil to flow through the piston. The rear piston is a linear/digressive and the .012 preload is similar to the angle cut on the face of the piston. The larger the preload the more force it takes to open the piston.

Now whether this is the ideal setup for you and your car is hard to tell. Is this the setup you have been using? It sounds like a typical VD setup.

[Numbskull XIV]

The shocks are 8760. They are early versions but are still a good choice.

The bleed is simply a .040 diameter hole in the pistons that allow oil to by pass the shim stank on the piston. The other information is details of what shim stack is on each side of the piston. Go to the Penske website and they will have information what the coding for the valve stacks are all about.

The 2 degree bump refers to an angle cut on the surface of the piston where the shim stack seats. The higher the angle the more force it takes to open the stack and allow oil to flow through the piston. The rear piston is a linear/digressive and the .012 preload is similar to the angle cut on the face of the piston. The larger the preload the more force it takes to open the piston.

Now whether this is the ideal setup for you and your car is hard to tell. Is this the setup you have been using? It sounds like a typical VD setup.

Thanks for the great information. This was the setup that was on the car when I bought it. According to the logbook, the car hasn't been ran since 2003 so I would suspect that the car is mostly "original".

Jon

[S Lathrop]

Given the age of the car and shocks, I would get in touch with http://www.srpengineering.com. They can give you advise on shock settings and guidance on setups to run with their shocks.

At a minimum the oil needs to be changed in the shocks.

Tires have changed a lot since the car was last run and you need setups and shock settings that suite the current tires.

[Pi_guy]

My .02
would be
Angelo Zarra <azarra@anzesuspension.com>
@ http://anzesuspension.com
or 516.671.3960