Shocks Question, How do they affect handling? Options

[Joe Ricard]

So now I see the MAJOR difference from Koni red externally adjustables versus the new Koni yellow sports.

Both are only adjustable in rebound. So what is it that is actually happening and what is the theory behind slower (firmer) shock dampening on handeling of the car.

The way I see it acceleration causes weight transfer to the rear of the car (if it gets to sliding mash the gas) squats the rear end and compresses the shock.

mash the brake and weight transfers to the front compressing the front and lifting the rear. Does the more dampening you have slow the weight transfer?

I know spring rates further complicate the whole thing.

So what I noticed/discovered was the effect that moving from 17mm to 21mm torsion bars and new Koni's in front reduced the nose dive under braking and somehow reduced the unloading of the rear wheels. Rear shocks Koni reds externally adjustable were full firm as always. fronts we set to 1/4 from full soft. seemed pretty good so we just left it alone.

[SLITS]

Ok Joe....Think of it as this way....as you roll into a corner, the suspension takes a "set".....as long as this "set" is controlled, the car is easier to drive thru the corner. If the car rolls in (suspension on the loaded side) compresses and on rebound the spring is allowed to extend rapidly, the car will feel uncontrolable in the corner (rapid camber changes)...twitchy....kinda like bad shocks. In reality, it is the rate of rebound you want to really control, 'cause the compression is taken car of by weight and force counteracted by the "springs".







How was that for bullshit?

[Aaron Cox]

smells like bullshit ron (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

i havent a clue about such questions. i just drive the dumb things (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[SLITS]

QUOTE (Aaron Cox @ Nov 7 2005, 04:17 PM)

smells like bullshit ron (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif) i havent a clue about such questions. i just drive the dumb things (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

And badly, I might add (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

Is this time for your picture?

[J P Stein]

Damned if I know. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
I do know that mongo serious AXers spend what it takes to get the best shocks available....double adjustables at minimun...Penske, Moton, JRZ....whut ever. 4k is entry level.

I also know that if I had all them knobs to fool with I'd fuck it up. I just had Bil. West revalve mine to whatever they thought best. I have enuff trouble with tiar pressures.

[Joe Ricard]

I'm with ya JP.... as always it seems.
I guess the reason for the techy "howz that shit really work" question is If I'm going to screw around with something I want to know what it is that I'm intending to accomplish.
Espeacially if I'm going to throw money at it. Nearly fell over when I priced a set of Koni Sports for the rear. How much is "No Longer Available" each Plus shipping? (IMG:http://www.914world.com/bbs2/html/emoticons/flipa.gif)
Found AJR stocks them and shipping is free.
Found the QA-1 brand aluminum rebound adjustables from JEG's and then thought Hmm what's up wit DAT.
No graphs to compare rebound rates. Which I believe should be valved to match or be able to control the spring rate.

My head hurts ... Thats what I get for thinkin into stuff and squeazing a dollar bill till the eagle screams "uncle".

Ron your Bull shit seems about what I thought too. (IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)

[phantom914]

Oversimplified: As far as turns, damping will affect handling balance at the moment you turn into a corner. As the car takes a set, the springs and swaybars affect the handling balance. So on an AX course, if you make the rear dampening very stiff, the car will oversteer more on quick direction changes.


Put another way, the handling balance on a skidpad (i.e. steady state cornering) can be tuned with springs and swaybars, but not shocks. Handling balance in quick directional changes are tuned with shock dampening.

The realtionship is the same as with springs and swaybars, stiffer dampening in the rear means balance towards more oversteer in quick transitions and vice-versa.

OK. I'm too lazy to type more, but if you want more confusion, I can probably arrange that. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)


Andrew

[Joe Ricard]

I also know that if you are screaming into a corner and the rear rebound is not firm enough you will get tail happy as the rear tires unload.
Dampening in rebound keeps the suspension from extending...... I guess.
which 1 keeps the rear tires on the ground during breakng and once you start to change direction.

[Don Wohlfarth]

QUOTE (J P Stein @ Nov 7 2005, 03:34 PM)

I also know that if I had all them knobs to fool with I'd fuck it up.

I agree with JP.
I installed single adjustable JRZ's front and back on my 2.8, semi tube 914 and made no other changes. I chased settings for a little over a year, maybe 15 track days.
Got it to handle OK but always felt there had to be more. No, I didn't fiddle with shocks after ever session but a couple times over a weekend. I'm a de inst so I'd always have at least 1 student and maybe a checkout ride for others. Add in a little discouragement with lack of "real" improvement.
Finally hit the right settings. Only realistic comment is Night and Day. (IMG:http://www.914world.com/bbs2/html/emoticons/boldblue.gif)
Picked up over 2.5 seconds on home track where I've got over 100 days.
JP's starting price may be a little low but well worth the investment.

[Joe Ricard]

QUOTE (Don Wohlfarth @ Nov 8 2005, 06:14 AM)

JP's starting price may be a little low but well worth the investment.

That will leave a mark.
on my frigging head if the wife knows I spent that much on my cars shocks.

Need new Hoosiers more than JRZ's

DAMN!!!!!!!!!!!!! (IMG:http://www.914world.com/bbs2/html/emoticons/drooley.gif)

[groot]

I'm in the middle of doing some damper tuning for an upcoming product. It's amazing what a little change will do to a vehicle's steering, handling and ride. We use take-aparts and re-valve them for each change.

Damping controls the transitions only! It can cause entry oversteer or understeer because it controls the loading of the contact patches. It will not fix any inherent imbalance in steady state cornering.

Rebound controls the vehicle's sprung mass and compression (jounce/bump... whatever) control the unsprung mass. With rebound adjustable dampers you can have too much or too little damping... more is not always better. For ride, ff you have too much damping, the vehicle will feel tuggy... it will pull down on the driver. For handling, too much rebound control will not load up the outside wheel as fast as the other end of the vehicle.... causing oversteer.

After typing this I realize it's best to let Koni tell you they're recommendation (from the Koni website):

QUOTE

Adjusting rebound Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound. The rebound damping controls the transitional roll (lean) as when entering a turn. It does not limit the total amount of roll; it does limit how fast this total roll angle is achieved. How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center heights, etc. It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering power) at that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as “jacking down.” This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered. This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer. STEP 1: With rebound set on full soft and the bump control set from your testing, drive the car one or two laps, paying attention to how the car rolls when entering a turn. STEP 2: Increase rebound damping three sweeps on all four dampers and drive the car one or two laps. Repeat Step 2 until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. Any increase in the rebound stiffness beyond this point is unnecessary and may in fact be detrimental. EXCEPTION: It may be desirable to have a car that assumes an over-steering or understeering attitude when entering a turn. This preference, of course, will vary from one driver to another depending on individual driving style.

I use Koni double adjustables on my race car... 8611s on the front and 30 series on the rear. Total cost for all 4 of the dampers <$1200. You don't have to get Motons or JRZs. There are other options that are far less expensive.

[Joe Ricard]

Nice thanks Kevin.
always value the teachings of someone who is out there doing it and succeeding.
Not to say some of the bench racers don't have valued input (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)