Front or Rear Sway Bar First for Track Days? How Sway Bars Change Balance

Front or rear sway bar first? It's one of the most common questions once a car starts going to track days or autocross. Sway bars are relatively affordable, they bolt on, and they change how the car feels more than almost anything else in that price range. But the wrong bar, or the right bar on the wrong setting, can make a car harder to drive.

This guide explains what a sway bar does, how front and rear bars change the car's balance, what adjustable bars and end links add, and how to choose where to start. We use aFe's and Eibach's own descriptions and instructions, including aFe's published rates for its GR86 set as a worked example. We won't tell you a "best" setting for your car, because aFe itself says handling also depends on alignment and tire grip.

What a Sway Bar Does

A sway bar (also called an anti-roll bar or stabilizer bar) is a torsion spring that links the left and right wheels at one end of the car. When the car leans in a corner, one side's suspension compresses and the other extends. The bar twists to resist that difference, which reduces body roll.

Eibach describes the effect in its own words: an anti-roll bar "reduces body roll" and "minimizes load differences between the outer and inner wheels when cornering." Because a bar only works when the two sides move differently, it doesn't add much stiffness when both wheels hit a bump together, unlike stiffer springs.

The part that matters for track balance: a stiffer bar at one end shifts more of the cornering load transfer to that end. Eibach notes that anti-roll bars "can also influence the handling characteristics like oversteer or understeer," and can adjust "the natural steering behavior in cases of understeer or oversteer."

Front vs Rear: How Each Bar Changes Balance

aFe's GR86 instructions explain the balance effect clearly. Stiffer roll resistance at one end puts more demand on that end's tires: "the higher the stiffness, the earlier the slip. If the front slips first, you will have understeer. If the rear slips first, you will have oversteer."

So, as a general guide:

• Stiffer front bar (or softer rear): the front tires tend to give up first, so the car tends toward more understeer.
• Stiffer rear bar (or softer front): the rear tires tend to give up first, so the car tends toward more oversteer, or less understeer.

aFe adds an important caution: "Handling characteristics highly depend on wheel alignment and how much grip your tires have." A bar is one tuning tool, not the only one.

Which Bar First?

The answer depends on what your car does now. That's why it's worth driving the car on its current setup and noting how it behaves before you buy anything.

If the car understeers at the limit (it pushes wide in mid-corner and won't turn in as you add steering), a stiffer rear bar is often where people start, because it moves balance toward the rear.

If the car is loose or oversteers (the rear steps out mid-corner or on corner exit), a stiffer rear bar is the wrong direction. You'd look at a softer rear setting, a stiffer front, or your alignment and tires.

If the car feels balanced but rolls a lot, a matched front and rear set can reduce roll while keeping the balance roughly where it is.

Remember aFe's note: alignment and tire grip matter too. If your tires are worn or your alignment is still the factory street spec, fix those first or at least at the same time. Our street car to track car order of operations covers where sway bars fit in the big picture.

Adjustable Bars and What the Holes Do

Adjustable bars let you change stiffness by moving the end link to a different hole on the bar's arm. aFe's instructions spell it out for both bars on its GR86 set: "The hole closest to the end is the softest setting." The hole furthest from the end is the stiffest.

aFe's GR86 set publishes the rate for every position:

• Front 1" bar, 2-way: 467 lbs/in (soft) and 575 lbs/in (stiff), which aFe lists as 211% and 283% stiffer than the stock GR86 front bar
• Rear 0.75" bar, 3-way: 320, 405 and 525 lbs/in, which aFe lists as 113%, 170% and 250% stiffer than the stock GR86 rear bar

aFe's "Suggested Initial Settings for Street" are front "Position #2 Full Stiff" (hole furthest from the end) and rear "Position #1 Full Soft" (hole closest to the end). That's aFe's street suggestion, not a track setting. On track, start there, make one change at a time, and note what each change does.

These rates are for the GR86 set only. Other bars, from aFe or anyone else, have different diameters, arm lengths and rates. Check the listing for your car.

End Links and Preload

End links connect the bar to the suspension. They matter more than most people expect.

aFe's GR86 set uses end links with "PTFE lined Aurora rod ends" that are length-adjustable. Adjustable links let you set the bar with no preload, meaning the bar isn't already twisted when the car is sitting still at ride height. aFe says its links "are also length adjustable if you want to adjust out any static pre-load in the rear bar." A preloaded bar can make the car behave differently turning left versus right.

On a lowered car, stock-length links may no longer suit the bar's geometry, which is one reason adjustable links are common on track cars. aFe's GR86 instructions include a good install tip: if the rear link is tight to fit, loosen the lower shock bolt a few turns to let the control arm open up, then retighten the shock bolt and end link bolts once the link is in.

If you lower the car with springs or coilovers, set the bar and end links after the ride height is final. See our guide to coilovers vs lowering springs.

aFe vs Eibach: What Each Offers

aFe Control sway bars. aFe's GR86 set (part 440-722001-L) is a front and rear package with CNC-bent tubular and solid bars, 90A polyurethane bushings, PTFE-lined Aurora rod-end end links and made-in-USA construction. aFe lists an install time of 2.5 hours. The front is 2-way adjustable and the rear 3-way.

Eibach anti-roll bars. Eibach positions its bars as a balance and roll-control upgrade made from cold-formed spring steel with a powder-coat finish, and its German site lists TÜV certification as included. Eibach's emphasis is on reducing roll and correcting understeer or oversteer tendencies, in its own words adjusting "the natural steering behavior in cases of understeer or oversteer."

Both brands offer vehicle-specific kits, and adjustability, diameters and included parts vary by car. Check the TRP listing for your vehicle.

Which Setup Fits Your Driving

Common Questions

Should I upgrade the front or rear sway bar first?

It depends on how your car behaves now. If it understeers at the limit, a stiffer rear bar is a common first step, because it moves the car's balance toward the rear. If the car is already loose, a stiffer rear is the wrong direction. Check tires and alignment first, since aFe notes they influence handling too.

Does a stiffer rear sway bar cause oversteer?

It moves the car in that direction. aFe explains that higher roll stiffness at one end makes those tires slip earlier, and if the rear slips first you get oversteer. Whether your car actually oversteers depends on how much you change and on alignment and tires. Start soft and adjust one step at a time.

Do sway bars reduce understeer?

They can. Eibach says anti-roll bars can adjust "the natural steering behavior in cases of understeer or oversteer." A stiffer rear bar, or a softer front, tends to reduce understeer. A stiffer front tends to add it. Which change helps depends on your car's starting balance, tires and alignment.

What do the holes on an adjustable sway bar do?

They change the bar's effective arm length and so its stiffness. On aFe's GR86 bars, "the hole closest to the end is the softest setting" and the hole furthest from the end is the stiffest. aFe publishes a rate for each hole. Other bars may differ, so follow the instructions for your part.

Do I need adjustable end links?

They're very useful on a lowered car or a track car. Adjustable links let you set the bar with no preload at ride height, so the car behaves the same turning left and right. aFe's GR86 set includes length-adjustable rod-end links for this reason. Set them after your ride height and alignment are final.

What's the best sway bar setting for track days?

There isn't one universal answer. aFe gives a street starting point for its GR86 set (front full stiff, rear full soft) but notes handling also depends on alignment and tire grip. Start there or on the softest settings, change one end one step at a time, and note what each change does.