adjustable Koni struts?

[Flieger]

Hi,

Are standard Koni struts with Koni inserts adjustable for rebound damping? I have heard about compressing the piston rod fully, then turning the piston to change the valve setting. Does this apply to the standard equipment for a 1971 911S?

I want to soften my front rebound damping to better match my car's light weight and stiff (relative to mass) suspension setup. I think this adjustment will help the tires stay on the road and griping in bumpy turns.

Thanks for any info.

[Flieger]

Upon searching the Pelican parts technical forum, it appears that the factory original Koni struts for a 1971 911S are adjustable for rebound via the turn-the-piston-rod method.

[RSTarga]

Have you tried loosening your front ARB? I think that would give you more effect than the rebound. What front torsion bars are you running? I'm running the Koni gas adjustables set at full soft with stock ARB and 21mm front torsion bars. My front tires are 205/55/16 so they have some sidewall deflection still.

[Flieger]

I have a Weltmeister front sway bar- I think 22mm because that is what the rear measures. Both bars are set pretty soft. I could slide the clamp a little farther, I suppose and I was thinking of doing that for more ultimate front grip but I do like the roll stiffness through esses where there is instant rotation. My tires are Yokohama Advan A048s which have pretty stiff sidewalls.

I want to soften the rebound damping because the car tends to "skip" over ripples in pavement, especially while braking. The car just feels like it is overdamped in rebound. The torsion bars are stock 19/23 but the weight reduction makes them almost too stiff.

My first priority is controlling the "skipping" over ripples. The added benefit of keeping the tire on the ground is increased cornering grip through left-right transitions, so that makes me happy.

Thanks for your suggestions.

[RSTarga]

Your torsion bars sound close enough to mine. I'm stiffer and don't have that problem. Maybe you need the shocks rebuilt. Are you running 29psi front 34 rear?

[Flieger]

They may well be worn-out. They look original.

I am running tire pressures ~30 psi cold front and rear. Rears gain about 4psi, fronts just about 2 when warm.

[Flieger]

You said your dampers are set full soft, which is the direction I want to go. I also see you have a Targa while my car is a non-sunroof coupe with a roll cage and some other chassis reinforcements. What does your car weigh? My car is much lighter than stock. These details make me think your setup is softer than mine so you would not have these road-holding issues.

[RSTarga]

I set my tire pressure cold at 29 and 34. I think your rear pressure at 30 is producing more heat and so going higher. Yes my car being a Targa flexes more but I think that the skipping over ripples would still be noticeable since I'm also running 21 torsion bars at the front which are harder than yours. I also am running elephant rubber bushes all around. Since I am running the Koni gas shocks the rears are full soft and adjusted like yours. The fronts come with a knob that is put ontop of the shock and turned to soften or harden. My car weighs about 2200lbs, a little lighter than stock.
I think you either need to rebuild your shocks or get new ones, sounds like they are a little tired. As reinforced as your car is you could use the bilstein HD's. I went for Koni gas so I could go a little softer.

[Neunelfer]

Max, I would encourage "Full Soft" on Koni's on the street as well. Perfect setting in my book.

[Flieger]

I have found that the struts have been serviced sometime in the past 15 years while this car has been undergoing its speed mods. They are probably about 8 years old. There are no leaks and I do not feel that I am hitting the bump stops. So, maybe they are not all that worn after all.

I think that the struts would likely have the standard replacement red Koni hydraulic inserts. There are no knobs for adjustment, so they are not the cool gas-charged ones.

I got an average price to re-valve these strut inserts from "True Choice Koni Racing" so I will see if I can fit this into my budget. This would be the best setup- tuned for my car's specifications. Otherwise, I will try to find softer rebound dampers I can for these Koni struts. I have been told by several mechanics, and all of you board members, that new Koni inserts are set just a little firmer than full soft when new. If that was the case with my car, I likely cannot get any softer with these dampers. I may have to go for the custom tuning or just live with the current roadholding.

The handling is certainly not "bad" even now. The bushings, bearings, alignment, and corner-balance should make the car drive even better. On smooth roads I will probably not need the softer dampers very often. I may use what is left of the limited budget on new front tires, which I need much more urgently.

Thanks for all of your suggestions. I have some thinking to do before the spring suspension service.

Happy Holidays