Glossary
What is an Anti-Roll Bar? How Sway Bars Change Handling Balance
An anti-roll bar (also called a sway bar or stabiliser bar) is a torsion spring connecting the left and right wheels of one axle. It resists roll without affecting ride stiffness in heave. Stiffening the bar on one axle increases that axle's share of lateral load transfer, reducing its grip, which is the primary tool for tuning understeer and oversteer balance without changing springs.
| Diameter | Relative stiffness | Change vs 20 mm |
|---|---|---|
| 18 mm | 0.66 | -34% |
| 20 mm | 1.00 | baseline |
| 22 mm | 1.46 | +46% |
| 24 mm | 2.07 | +107% |
| 26 mm | 2.86 | +186% |
How bars change balance
Total lateral load transfer in a corner is fixed by the centre of gravity height, track width and lateral acceleration. What setup controls is how that transfer is distributed between front and rear axles. Because a tyre's grip grows less than proportionally with load, the axle that takes more of the transfer loses more grip. Stiffen the front bar and the front loses grip first: understeer.
Adjusting an anti-roll bar
Most race bars have multiple link holes along the arm, or rotating blades. Moving the link closer to the bar shortens the lever and stiffens it. Disconnect the bar when corner weighting, then reconnect with the drop links adjusted so there is no preload at static ride height.
A bar that is too stiff can lift the inside wheel in slow corners, which costs traction on a driven axle. On very bumpy circuits a softer bar lets each wheel follow the surface independently.
Frequently asked questions
Should I adjust bars or springs to fix balance?
Bars for balance in steady-state cornering; springs when the problem is pitch, aero platform or ride over bumps. Bars are quicker to change between sessions.
What does disconnecting the rear bar do?
It moves roll stiffness to the front, so the rear gains grip and the car understeers more. It also increases roll, which can hurt camber control.
Why does my car lift the inside front wheel?
The front roll stiffness (springs plus bar) is high relative to the rear, so the front inside wheel unloads completely. It is usually a sign the front bar is too stiff for the circuit.
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