Adjustable Dampers - But Perhaps Not as We Thought Captan?

[Knightrider 1]

Hi Everyone, here are a couple of really interesting articles (blogs basically) by a US guy who is a damper guru. Raced Jap stuff, but did a load of research:

http://farnorthracing.com/autocross_secrets6.html

http://farnorthracing.com/autocross_secrets18.html

It is REALLY technical, but worth a read. The totally scary thing is how variable even new dampers (ordinary or coilies) are out of the box, especially on rebound, and how irregular the adjustment can be - clicks version or Koni smooth turn version.

Here is a lift from the website:

Amazingly, save those brands mentioned in that earlier list, this was a non-stop parade of horror, including, but not limited to:

1. Adjusters that did absolutely nothing;

2. Adjusters that had more crosstalk effect than they had primary effect (ie, a rebound adjuster where 1 click made a 10% change in rebound and a 30% change in compression);

3. Adjusters that were nonlinear and exponential;

4. Adjusters that peaked in the middle of the adjustment range (in one example, "full hard" was softer than "full soft");

5. Shimstacks assembled upside-down;

6. Sets of shocks where a front and rear shimstack had been exchanged;

7. Shocks valved with forces that were insane (1600 lbs/in @ 3 in/sec was the record);

8. Shocks that faded so fast (as they warmed up) that no two runs were ever alike;

9. Shocks with adjusters that varied by 10% on the same shock at the same setting, depending on if you got there by going harder or softer; and

10. Shocks that adjusted rebound and compression in lockstep, but had so much compression that backing them down to reasonable levels made rebound way too soft (very common with the Japanese brands like GAB, JIC, Tein, etc)

So if you want to do track days or the Ring you need to get dampers checked on a dyno – it is not expensive – so that you know whether a set of dampers a) are really 'matched' with respect to bump and rebound and how the adjustment works relative to each damper.

Read the stuff from the guy in the US.

Hope this is useful. I do think a lot of members struggle with some of the technicalities with respect to suspension/dampers, which are after all critical to improving our lovely motors and cost loads and maybe we could be better 'informed'.

[Dragon Dave 1]

Well, I wish I had read this before I got my Koni adjustables. I have the yellow sport dampers, when I purchased them they said in the advert that they are adjustable so that you can set the dampers hard or soft, 'however you like'. In the picture of the shocks it shows the front shock with the knob on top to adjust it. It doesn't show the rear shocks and nowhere does it say that you can't adjust the rear shocks whilst on the car. (You have to take the rear shocks off the car to adjust them).

So after having them fitted, the rear suspension was too soft. If I go too fast round a corner, the arches rub and I can't even put one person in the back without rubbing.

Today I have taken off the rear shocks and made them stiffer. It took about an hour to do the whole job. The adjuster has 720 degrees of adjustment but most of it does nothing and the last half a turn has all the adjustment. When I turn the rod all the way, it locks and then will not extend out of the body, so I turned it back just enough for it to slowly slide out.

It's a lot better now but still not perfect. The arches still rub when I go fast round corners but not as much as before. The shocks are harder but in the advert it says they can be 'solid', they are not solid.

Now I wish I hadn't bothered with the adjustable dampers, I should have got some that are already setup right. It seems silly that they sell me lowered suspension with adjustable damping but even on the hardest setting it doesn't work right.

The front suspension is top adjustable and works ok. On the stiffest setting it is near enough solid and even on the softest setting the arches don't rub.

Maybe I have adjusted the rear ones wrong? Or maybe they are faulty? Does anyone else have any experience of yellow Koni adjustables?

[Dragon Dave 1]

I have now taken the 20mm spacers off the rear and the car drives much better. There is no rubbing at all.

I have had the rear arches trimmed back on the inside lip and I'm running on 8Jx17 rims with 205/40/17 rubber.

I will try some 15mm spacers and see if that works.

[Knightrider 1]

Dave, as far as I'm aware the adjustment, be it on or off the car, is only for the rebound, NOT the compression. So the issue with the car 'sitting' and tyres rubbing the arches won't go away by adjusting them stiffer. The main thing that I thought was interesting in those items that I posted links to was how unreliable the adjustment was. So if you give both fronts a 180 degree turn from 'least' and assume that the rebound will now be identical left and right....it potentially won't be. Incidentally, the guy reckons that KONIs are actually better than most others.

I've sent my 'bought used' fronts to Paul Drake and asked him to put them on his dyno to a) tell me if the compression is matched set them up so the rebound is identical, on the same 'softest' setting. I.E. left might be at full soft but right might be at say 90 degree turn 'up' to make them match.

I think the info on the links is so fundamental that it should be made a sticky.