Most adjustable sway bars spend their entire lives in whichever hole the installer happened to reach first. That is a waste of the part. The adjustment is the reason to buy an adjustable bar, and using it properly is the difference between a car that rolls less and a car that actually behaves the way you want it to.
This is a guide to using that adjustment on a Porsche specifically, because the rear-engine layout changes which direction you should be moving in.
What does moving the end link to a different hole actually change?
A sway bar is a torsion spring that ties the left and right sides of an axle together. When one wheel moves up relative to the other — which is what happens in a corner — the bar twists and resists that difference. That resistance is roll stiffness.
The adjustment holes change the leverage the suspension has over the bar. Mounting the end link closer to the bar's centre shortens the lever arm the suspension is working with, so the same wheel movement twists the bar harder. That is the stiff setting. Moving the end link out to the far hole lengthens the lever and softens the effective rate.
The bar itself does not change. What changes is how much of it the suspension has to fight. That is why a two-position bar gives you two meaningfully different cars and a three-position bar gives you three, without buying anything else.
Adjustment range varies by part. The 991 Carrera front and rear kit is 2-way adjustable at both ends. The 997 Carrera rear bar is 3-way. Check the product page for the part you are running rather than assuming.
Should I stiffen the front bar or the rear bar?
This is the whole game, and the rule is simpler than people expect: the end you stiffen is the end that loses grip in roll.
Stiffen the rear bar and the rear axle carries more of the roll resistance. Load transfers across the rear axle more abruptly, the inside rear unloads sooner, and the car rotates more willingly. More oversteer, sharper turn-in, less understeer on corner entry.
Stiffen the front bar and the same thing happens at the front. The front axle gives up grip first, the nose runs wide, and the car feels more stable and less willing to rotate. More understeer.
Softening works in reverse. Softening the rear is the same directional change as stiffening the front.
You are not adding grip with either move. Total mechanical grip is set by tires, dampers, geometry and how much load the car can put through a contact patch. The bar decides how that grip is distributed between the two ends. It is a balance tool, which is exactly why it is such a good first modification — it changes behaviour without changing ride height or ride quality.
Why the rear-engine layout changes where you should start
A 911 carries roughly 60% of its mass behind the rear axle. Two things follow from that.
The first is enormous rear traction under power, which is why these cars put down more than their tire width suggests they should. The second is a large polar moment of inertia — a lot of mass a long way from the car's centre. Once that mass starts rotating it wants to keep rotating, and it takes longer to catch than it does on a front-engine or mid-engine car.
The practical consequence is that a 911 already rotates more than most cars, and the rear bar is the most powerful lever you have over that. Stiffening the rear of a 911 is not the same experiment as stiffening the rear of a front-engine sports car. The same click of adjustment does more, and it does it in the direction the car was already inclined to go.
Start with the rear bar in its softest setting. Drive it there. If the car understeers more than you want, you have room to move. Starting at the stiff end and working back means your first few drives are spent in the least forgiving configuration, which is the wrong order for learning a new setup.
The same logic applies to the mid-engine cars in a milder form. A 987 Cayman or Boxster is far more neutral than a 911 and tolerates a stiffer rear more happily — but it is still a car with its mass behind you, and the same starting discipline is sensible.
How do I test a change without fooling myself?
Suspension testing goes wrong because the test conditions move more than the setting does. Tire temperature, tire pressure, fuel load, surface temperature and your own mood all change from drive to drive, and every one of them is capable of masking a bar adjustment.
What helps:
- Change one thing. One end, one hole. If you move the front and the rear at the same time you have learned nothing, because the two changes partially cancel.
- Use the same corner every time. Pick one reference corner you know well, ideally a long constant-radius one where balance shows up clearly, and judge the change there.
- Set tire pressures cold, the same way, every session. A few PSI moves the balance as much as a bar hole does.
- Warm the tires first. A cold tire tells you about the cold tire, not about the bar.
- Write it down immediately. Hole position front and rear, cold pressures, hot pressures, what the car did. Memory is not evidence.
Do this on track or at a driving event. A public road has traffic coming the other way, no run-off and no consistency, and finding the limit of a new balance setting is not something to do with an oncoming lane a few feet away.
Do I need an alignment after fitting sway bars?
Fitting a bar does not by itself change static camber, toe or ride height, so a bar-only change does not automatically require an alignment the way a spring change does.
Two caveats. If you are fitting bars as part of a complete kit with springs, the ride height changes and an alignment is mandatory. And if the car has not been aligned recently, a new balance setting is a good moment to have it checked — you cannot tune balance meaningfully on top of an alignment that is already out.
Whatever the alignment shop finds, the final settings are their call, made against your tires, your ride height and how you actually use the car.
What will sway bars not fix?
Bars control roll. They do not control anything else, and a bar is the wrong answer to several common complaints.
They do not fix a floaty or crashy ride — that is damping. They do not fix a car that dives under braking or squats under power, because those are pitch movements where both wheels on an axle move together and the bar barely twists at all; that is springs and dampers. They do not add grip, they redistribute it. And they will not rescue worn bushings, tired dampers or old tires.
A stiffer bar on a car with worn dampers usually feels worse, not better, because it asks the dampers to control load transfer they were already struggling with. Damping sets the ceiling on what any bar setting can achieve. If the car is on high-mileage original dampers, sorting that first will do more for it than any hole position — check the suspension catalog for the damper applications listed for your car.
Which bar actually fits my car?
Porsche sway bar fitment is narrower than most people expect, and this is where orders go wrong.
On the 997, the bars differ between manual and PDK cars — there is a separate manual rear bar and PDK rear bar, and they are not interchangeable. Several kits are RWD only. Some exclude PDCC, Porsche's active anti-roll system, because a car with PDCC has hydraulically actuated bars rather than conventional ones. Turbo models are frequently excluded from Carrera kits.
Every product title in the sway bar collection states its restrictions, and the full manufacturer application list is on each product page under Compatible Vehicles. If your exact configuration — model, year, drivetrain, transmission — is not named on that list, the part is not for your car.
Common questions
Can I run a rear bar without a front bar?
Yes, and it is a legitimate way to target one specific trait. A rear bar alone on a 911 will make the car rotate more; a front bar alone will calm it down. Buying both ends gives you the full adjustment range in either direction.
Will an adjustable sway bar make my Porsche ride worse?
Not in any meaningful way over normal bumps, because when both wheels on an axle rise together the bar barely twists. You may notice slightly more of a single-wheel impact — a pothole or an expansion joint on one side — being passed across the car. Ride height and ride comfort are unchanged.
Should I set the front and rear bars to the same position?
There is no reason to expect matching hole positions to produce a balanced car. The two bars have different diameters, different lever geometry and different jobs. Set them by how the car behaves, not by symmetry.
How do I know if I have gone too stiff at the rear?
The car starts rotating earlier than you intended, especially when you lift mid-corner, and the inside rear tire starts lifting or spinning up on corner exit. If the car feels nervous rather than responsive, go back one position. Responsive is the goal; nervous is past it.
Should I fit bars or dampers first?
If the dampers are healthy, bars first — they change balance for less money and less labour. If the dampers are tired, they come first, because a worn damper masks or undoes whatever the bar is trying to do. Check the application list for your car before assuming a damper is available for it.
Do sway bars help on the road or only on track?
They help on the road, and for many owners they are the best single change available, precisely because they alter how the car turns without touching ride height, ride quality or ground clearance. Road settings are generally softer at the rear than track settings.
An alignment is required after any change in ride height. All Eibach bars are made in the USA and supplied with mounting hardware.