Are my Koni's dead?

[Tom C.]

Just started putting my rear suspension together and when I went to check the setting on my Koni's (Classic) I noticed after compressing the shocks their was no rebound. They basically just stayed fully compressed. I also noticed when I spun them back and forth I could hear the oil inside the shock splashing around like it was water.

So are these shocks dead?

Funny thing is this is a car that I've been driving prior to my suspension rebuild and I never noticed anything unusual. What the heck?

[Tom C.]

I think I found the answer to my question. The fact that these are oil filled shocks rather than gas means that they will not rebound after full compressing them.

Is this correct?

[Flieger]

The adjustment procedure for Konis involves compressing the piston rod and then turning it to engage the fluid control valve. This is how the damping is changed.

Maybe you put them into the adjustment range? How many miles are on the dampers?

[Flieger]

And, I will look forward to seeing you around town sometime.

[Tom C.]

No I don't think I engaged the fluid control valve. I never turned the piston rod. I just thought it was interesting their was zero rebound. The Koni's have less than 8K miles but were purchased new and installed 7 years ago. So the car was basically a garage queen for that time (PO ownership).

Based on the fact that these Koni's are oil filled I'm thinking they are not a good match for the other suspension mods I've done recently. Elephant PB bushings, monoballs, and 26mm TB's should create a rear suspension that is very active (ie. no binding).

Does this rationale make sense?

So I'm considering stepping up to a set of Koni Sports which I understand are a gas shock and externally adjustable.

What do you think about those Koni Sports?

The plans for the front suspension will be Elephant PB bushings, monoballs, and 21mm TB's.

Front and rear sway bars are still unknown as I'm searching for a solution that will not require cutting the body as some front adjustable sway bars need. So I'll probably end up with 19mm Weltmeister's front and rear.

[Tom C.]

Yup . . . you should come on by the house some time and have a look at the mess I've been making in the garage.

Finally finished my 2.5 short stroke, TRE is building my 901, Harvey is doing my wheels, TRE also doing a set of 911R replica seats, and I'm trying to get the suspension done.

Could have used you earlier today fighting with a control arm and a very tight fitting monoball.

And best of all the fridge is always full of beer.

I'll send you a PM with my contact info.

[Fishcop]

I stand to be corrected, but don't the dampers "damp", and the torsion bars/springs "compress and rebound"?

[Tom C.]

Your probably right. I was referring to the action of the shock . . . independent of the rest of the suspension.

[jpnovak]

Your observations about the shock not returning are perfectly normal. Koni's are not gas charged and will not return to an extended state after being compressed. Depending on where you have the adjustable rebound set you may have to pull back slowly but with much force to return them to the extended state. The rebound will adjust from "about the same as compression" to "nearly impossible to pull out by hand". Rebound adjustment is made by fully compressing the shock, rotating slightly, noticing the engagement point of the adjuster, and counting clicks CW or CCW.

The torsion bars (springs) provide the force to return the shocks to the extended state while on the car.

[Tom C.]

Thanks . . . thank makes sense to me now. I'm still going to check into availability of Koni Sports. I've checked the usual places (PP, Performance Products, Paragon, Koni website) and can't find a listing for my car. Seems odd they would not have an application for my car.

[Flieger]

What size are your rear torsion bars and what does your car weigh?

Stiffer torsion bars and less weight, sprung or unsprung, increases the natural frequency of the spring-mass-damper system.

If you have gas-charged dampers, you may be underdamped in the first portion of suspension travel. Depending upon you car's intended use, the wheels may not be controlled enough for track use or high performance street driving.

The wheels or body depending, on relative masses, will occilate for a greater number of cycles before returning to the equilibrium position when underdamped.

[Tom C.]

The rear TB's are 26mm and the car weighs 2100lbs (+/-). Your right about the suspension occilating if the shocks can't properly dampen out the effect of the TB's. Which is why I now understand why shocks and TB's need to be considered as a 'system'. This is also why I'm going to step up up from the Koni Classics to Koni Sports (external adj) in the rear and Koni twin tube gas shocks (external adj) for the front.

I just don't think the Koni Classics are a good match for TB's that are much larger than stock 19/23.

By the way . . . had a nice talk with Jason @ Paragon today. Wealth of information and explained how to retrofit shocks for a later model Porsche onto my 69E. Simply need to make sure you have the proper gland nut for the struts and a 2mm sleeve for rear eye mounts.

I'll post more next week after I get the shocks setup.

[barney911rs]

Tom,

Call and talk to Jason at Paragon. He was able to come up with a Koni Sport for my 73. Because it was a dedicated track/race car, he had some custom valved. You can tell him I sent you if you want. They had the adjuster on the top with the small plastic knob to turn them. I was very happy with them.

[Won]

Originally Posted by jpnovak

Your observations about the shock not returning are perfectly normal. Koni's are not gas charged and will not return to an extended state after being compressed. Depending on where you have the adjustable rebound set you may have to pull back slowly but with much force to return them to the extended state. The rebound will adjust from "about the same as compression" to "nearly impossible to pull out by hand". Rebound adjustment is made by fully compressing the shock, rotating slightly, noticing the engagement point of the adjuster, and counting clicks CW or CCW.

The torsion bars (springs) provide the force to return the shocks to the extended state while on the car.

Just for future reference, Koni Sports are gas charged shocks. This is from their FAQ:

Q: KONI makes some shocks that are not gas shocks. Why?

A: There are basically three types of shock absorber designs: mono-tube high pressure gas, twin-tube low pressure gas and twin tube hydraulic (non-gas). Each of these designs has a certain ride and performance characteristics that can enhance the performance of a vehicle and KONI is the only company that makes three designs. KONI ride development engineers evaluate each new vehicle and can decide which shock design would best apply to that vehicle. Some cars respond to mono-tubes, some like gas pressurized and others don't. Most shock companies utilize only one or two of these style because it is less expensive for manufacturing but are therefore limited in design capability and function.

[rfn026]

Pushing down on your shocks really doesn't tell you much. At best it tells you only about what's happening at the slowest possible shaft speed. Most shocks are very different with high speed shaft movement.

The only way to really make an assessment is to put them on a shock dyno. After you check the results you can have them revalved to meet your personal needs.

Richard Newton

Autocross Performance Handbook

Wheel and Tire Performance Handbook

[djdsc]

The newer KONI "reds" that are gas and oil filled should be marked. They will fully extend when compressed.