Jittery front end

[BSNMOE]

My 73 911S has hollow, 21mm front/26mm rear torsion bars, 7X15 rims with 205/60's. Sway bars stock (15mm ft & rear). Koni equiped from the Factory, but rebuilt along with suspension bushings 8 yrs ago.
My origional Koni setting was one turn up from soft. There are 2 1/4 turns from full soft to full hard.
At this setting, with less than 1/2 tank of gas, the front end is what I call jittery(bounces up & down) while driving.
I turned the fronts up another 1/2 turn for 1 1/2 and that seemed to tame the front end, but I still do detect some oscilating.
Is it possible that I need to turn up another 1/2 to almost full hard to match these torsion bars?
And if so, should I match the front settings to rear? Some seem to perfer the rear setting a little more stiff than the front which would be close to full hard.

[Flieger]

Stiffer springs need stiffer dampers. Torsion bars get stiffer according to their diameter to the 4th power, so work out how much stiffer than stock each spring is, then you will need to go that same proportionally stiffer on the dampers.

[RWebb]

21/26 ??

also, how old are the suspension bushings?

tires? balanced? aligned?

[Tidybuoy]

You may have to experiment in 'less" than full turn increments. I found that on my car, on full soft, the car bounces and on full firm, the car hops. I drove the same freeway about 10 times and changed 1/4 turn increments and finally found out what works best for my car. my point is that you can have a terrible ride on either setting (soft/firm) and finding the best setting can take some experimenting.

[BSNMOE]

Originally Posted by Tidybuoy

You may have to experiment in 'less" than full turn increments. I found that on my car, on full soft, the car bounces and on full firm, the car hops. I drove the same freeway about 10 times and changed 1/4 turn increments and finally found out what works best for my car. my point is that you can have a terrible ride on either setting (soft/firm) and finding the best setting can take some experimenting.

That's what I'm finding out. I set the fronts and rears at 1/2 turn turn from full hard, which is 1/4 turn stiffer than my last setting. At this setting the front end jitters are tamed, but any inperfections in the road I feel. My tire pressures are at 29/34 and I do detect a slight bounce while looking for bumps in the road.

[ivangene]

how did you arrive at 21/26 numbers?

the front seems too stiff but I am not in an early car...

Tire pressure, and shock setting might take some trial and error. Also has it been lowered and did you put in a bump steer? those feelings translate strangely and might be contributing to the problem

[Tyson Schmidt]

If these are Koni Classic inserts, then you will likely need to go almost full stiff to match the 21mm torsion bars.

Probably 1/4 to 1/2 turn from full stiff. These are the type that you have to compress to turn the shaft for adjustment, correct? Non gas pressure, just hydraulic, correct?

Also make sure that the car isn't lowered to the point of riding on the bump rubber.

[BSNMOE]

ya, these are just hydraulic. i'm at 1/2 from full stiff now which tamed the front end untill i'm at 1/2 tank or less. I'll go another 1/4 stiff today.
the car is at 25in front with 24 1/2 rear with 1/2 tank, with a full tank the front drops down a little.

As for the poster above, I went with +2 on the torsion bars. With 7X15 0n 205's you need to upgrade t bars along with neg camber. Bump steer kit also.
at times I use 28 front and 33 rear tire pressure for a better ride(with my wife)

[Flieger]

If the car gets more jittery with less fuel then it would be getting overdamped (or rather not underdamped enough). Need to back off a bit to find a compromise between full and empty tank.