Which shock-absorbers to choose?

[Ole Petter]

Hi, my '75 911S was struggeling in the corners at the last track-day outing...
The car is generally very comfortable (in relative terms) when it comes to soaking up pot-holes and bumps in the road surface. This is a good thing as I have a serious back-problem with arthrosis eating away at my lower back. (Yes, I have had surgery but it seems like there is really no cure for me). Problem is I want to use the car a bit on track as well as on the road. So - I am keeping the standard torsion-bars and sway-bars.
Question is would Koni be a sensible proposition? Or - will they give me problems in DD beeing too harsh in the softest setting. The track I am driving at is silky smooth, so here a stiffer damper would bee a real bonus, me think.
I have tried Bilsteins on a Volvo Turbo, but found a bit too much...

The car has black (Boge) front shocks and blue (Spax or Woodhead licence built Boge?) at the rear. I find the rear shocks beeing excessively worn, giving the car poor "control" or precicion.

I really want to try the adjustable Konis, but maybe the wisest thing would be to fit new Boge shochs? Of course they would improve the car very much as vell!

Many thanks for your experience and help

Greetings, Ole

[fred cook]

Ole,

It sounds like the adjutable Koni shocks might just be the way to go. That way you could crank them to the firm setting for track use and still have a reasonable ride on the street. If the shocks on your car are worn, even the replacement Boge shocks would help the handling. Good luck with your project!

[Zeke]

A funny thing happened to me when I had my '73. When I got it, it rode hard. It was nasty. I started in on a rolling restoration and rebuilt the suspension at one point. I used 21/26 bars, 19mm sways and installed Koni Sports adjusted one turn up from the softest setting.

The car rode much better! I mean it was not bone jarring at all, yet it handled at the track very well. Not a full on race car, but it held its own. It's all in matching components. If you have heavy bars and soft shocks, the bars will overcome the shocks and the car won't handle well. If you have heavy shocks and stock bars (a mistake a lot of people make), the shocks will overcome the bars and the car will ride rough.

If everything is nicely matched and balanced, the car will feel gentle when it's really a bit of a wolf in sheep's clothing.

[Ole Petter]

Then maybe the Konis!
I was hoping they could help fight sway in the corners in the harder settings, and be "comfortable" in the softest. Then of course, the Boges is the safe alternative...
Beeing more comfortable in every condition.
But the Sport Konis is built like the Boge Gas? (Bruce Anderson) and with the added bonus of ajustability should be the best?

Maybe the Konis in the softest setting aren't any stiffer/harder than the Boge.
Has anyone tried both?

Again, many thanks for advice.

[Ole Petter]

I forgot to mention the weight of the car. It is a 1975 911S with its original 2.7 engine, mag case and mag gearbox housing.
The car has a weight of about 1020 kg with all but fuel.
As such the 23 mm original torsion bars ought to be firm enough?
Also the car has the sport option 20 mm front and 18 mm rear sway bars.
If the Konis are too firm, then switching to 26 mm torsion bars at the rear might do the trick? Or at least something to try.
The car has the Porsche recommended ride hight measured from the senter of the wheel and torsion bar axels...

[Zeke]

Well, good that you posted the car's setup. Wheel width etc., has a lot to do with this. Your car will set up similar to any narrow rear car. Are you running 6's and 7's or 7's all around? This has an effect on t-bar rate. I can't say enough about not having one component out of whack with the others. If your shocks are purely worn out, certainly a new set will help tremendously. Shocks by themselves will not level out a car in a corner. They can be made harder to compress, but they compress nevertheless during the corner. The sway bars (which should be called anti-roll bars) do that job.

The secret is to manage wheel travel and body roll so that your tires remain, for the most part, in contact with the track surface. Too high of a rebound rate and the car may skip a bit. Too high of a compression rate and the car will be very rough, and skip.

Bear in mind that the Koni Sports are adjustable externally. The KonI reds have to be disconnected from the body in the rear and the top nut removed in the front, both having to be fully compressed.

Has the car been aligned and corner balanced? What tire pressures did you use? These are all questions to address the rear end stability. An, of course, there's always the tendency of a 911 to want to come around on throttle lift in a corner. In a way, and when you learn to drive a car like that, it's a good thing. However, massive amounts of suspension work won't change that characteristic overall.

[Ole Petter]

The car has the original 6" Fuchs wheels fitted with 205/55-15 by the previous owner all around.
This is a very low-budget thing, the main focus is to keep the car in full health mechanically. The body is in outstanding shape, but of course beeing 33 years old time is taking its toll... I wish to carefully upgrade the car over time, and want to to the right choices for the future. So if I get yellow Konis for the much wanted adjustability it is something I will want to take further advantage of when I have money to update more of the suspension!
But, and there is a but, that is the situation with my bad back. I must have a car that I can drive for some distance and for fun... If it gets to harsh suspended then I can not use it much, and it will really be a bad situation...

[911pcars]

+1 with Milt on this one.

You can start with the adjustable Konis and see how that affects both street and track usage. If okay thus far, I'd progress to slightly larger torsion bars (21/F, 26/R). As Milt says, the slightly larger TBs along with the upgraded shocks will result in a slightly firmer ride, but not jarring. The shock settings and sway bar settings have more of an affect on ride harshness than the T-bars.

Sherwood

[Zeke]

Originally Posted by 911pcars

+1 with Milt on this one.

You can start with the adjustable Konis and see how that affects both street and track usage. If okay thus far, I'd progress to slightly larger torsion bars (21/F, 26/R). As Milt says, the slightly larger TBs along with the upgraded shocks will result in a slightly firmer ride, but not jarring. The shock settings and sway bar settings have more of an affect on ride harshness than the T-bars.

Sherwood

Just to clarify, my '71 rode better (read comfortable) when the suspension was finished with the recommended parts I listed. I could have gone a bit heavier on the sways and it wouldn't have affected the ride, but I was more or less unwilling to take the chance that they would rip out of the chassis as they sometimes do. There are kits for this, but I was happy enough with the 19mm on the front and rear.

You might also do a little research on sways. Using a 20mm on the front, and did you say, 18 on the rear (?) could be a contributing issue. It seems like these cars like to get real light on the inside front wheel in a corner to get planted. I really don't know on that one.

[Ole Petter]

Ok, so I will try out the ajustable Koni dampers.
Then the next step will probably be ajustable sway-bars, then it will be possible to fine-tune more at the track. Hopefully the car will remain comfortable as a road-car as well. Which maybe matters most to me...
Thing is as we all know, when at a track, the frustration of not beeing able to follow - or better overtake!? other cars is a major pain and of course can lead to excessive expenses...
So better do the right thing from the start. And ajustable dampers should be a help!

Ole

[IROC]

Originally Posted by milt

Bear in mind that the Koni Sports are adjustable externally. The KonI reds have to be disconnected from the body in the rear and the top nut removed in the front, both having to be fully compressed.

Not sure if I fully understand, but my front Koni reds do not have to be compressed to be adjusted. Just twist the adjuster.

I have Koni reds on my 2400 lb '76. I have the rears set one click from full stiff (to somewhat offset the weight of the 3.2) and I leave the fronts at full soft on the street and set them to full stiff on the track. Definitely a noticeable difference in ride quality between the two settings.

[Ole Petter]

Hi IROC thans for your experiece!
I understand that all the yellows are ajustable, and that some of the reds are too? You confirm that...
But about the ride of your car with the reds, what sort ot shocks did the car have previously? Did the ride get much stiffer/harsher with the Koni dampers, or did the adjustability give the possibility to be both softer and harder than before?

I found an old road-tests from '74 from Car and Driver which described a 911S with the optional Koni dampers (otherwise standard car) as: incrediblty flat and taut, soaks up the bumps - excellent!

I guess taut doesn't mean harsh, which it should not...

Thans for all the advice!