koni red fronts, dampen on rebound only?

[ghost1001]

Hi All,

I am in the process of assessing my suspension (1976 911s) for upgrade/rebuild. I pulled the koni front inserts, # 86R-1942, they look original.

They appear to dampen on rebound only. Meaning, when I push the rod into the case it slides in with very little effort. When I try to pull out the rod it is very hard, I can move it out by hand but very slow and much effort.

So it appears that when the car hits a bump the shock offers little resistance for the wheel going up and then dampens the rebound of the spring/torsion bar for the wheel going down.

Is this the way these should work, or do I need to replace.

Also, any input on koni replacement inserts if needed would be appreciated.

Thanks

[cgarr]

They should not collapse that easy, I just checked a set I have here and from feel they seem to be around 50/50

[ghost1001]

Was kinda thinking they should work (dampen) in both directions....but what do i know.

[Flieger]

All dampers should dampen in both directions. Most of the standard dampers for Porsches (not racing or custom-valved) should be close to 50/50 by feel, though the actual valving may be quite different, I do not think you can feel the actual percentages.

The Konis from early 911S are adjustable for rebound only. They also make externally adjustable gas dampers now that have both compression and rebound.

[356RS]

I always though that was the design of the early Konis, to damper only on rebound?

[Flieger]

Dampen both ways, adjust only rebound.

[KTL]

He just chose the wrong use of words to ask his question. Of course the shock dampens on both compression and rebound. I suspect his question should have been "does the adjustment of the shock only affect rebound?"

My adjustable Koni sport yellow shocks are only rebound adjustable. On compression they do indeed compress quite easily and on rebound the shaft is much harder to move depending on the the amount of "firm" dialed-in.

Contact Truechoice Motorsports or Jason at Paragon Products if you have specific application questions. Truechoice is a Koni rebuilder/customizer/specialist and Jason has a good feel for Porsche applications.

[Flieger]

Truechoice Koni Racing Services

[356RS]

Thanks Max. I worded that wrong.

[ix0ifan]

Originally Posted by ghost1001

So it appears that when the car hits a bump the shock offers little resistance for the wheel going up

I would think a 50/50 Bump/Rebound wouldn't be great and that a ratio of somewhere between 2 and 3 :1 would be appropriate.

If the bump rate is too high then the force requred to make the wheel move upwards will be relatively high and the car will be easily deflected.

The Koni concept of not adjusting the Bump rate is to do with the belief that in this direction the biggest effect on the required damper rate is the unsprung weight of the wheel. This does tend to make standard Konis a bit limited if you are radically changing wheel/tyre combinations. This has led to the mistaken belief that the Koni only provides damping in one direction.

During the last twenty years it has been more common to make single adjustable dampers that change rebound an bump in a fixed ratio.

I think that with a 'Classic' Koni if you set the damper to 'fully soft' the bump and rebound will be around 50/50.

If you adjust 1/2 a turn you will increase rebound by about 10-15%

If you adjust 21/2 turns you will increase rebound by 25 -30%

If you adjust 31/2 turns you will increase rebound by 50%

41/2 turns will be around 75-80%

It is possible that you couild get up to 5 turns which would be 90%

The reason you have a different 'subjective' feel to the force needed to move the piston rod in the two directions is probably to do with how the damper is adjusted.