In-car adjustments: brake bias, ARB, and more mid-race

In a typical iRacing GT3 stint you have four things you can change without coming to a stop: brake bias, the front and rear anti-roll bars, the traction control and ABS levels, and the throttle/engine map. Ovals add a fifth, the weight jacker. Everything else — the differential, springs, dampers, camber, ride height, wing — is set in the garage and frozen for the stint. Knowing which list a setting belongs to is half the battle, because plenty of drivers waste time hunting for a live diff control that does not exist.

The reason any of this matters: the car you qualified is not the car you race. Fuel burns off and the balance shifts. Tires heat, peak, and fade. The track rubbers in over a long race. The live adjustments are how you chase those changes instead of fighting them.

Brake bias — the one you will use most

Brake bias is the live knob fast drivers touch most often. The mechanism and which-way-to-move logic live on the brake bias page; here is the in-race usage.

As fuel burns, move bias rearward. The tank usually sits forward of center, so a lighter car is a more nose-light car, and a touch of rearward bias restores the entry feel you had on a full tank. The community method is consistent: move it back a click every few laps until the rears just start to lock under threshold braking, then nudge it forward one. One driver summed up the whole routine as moving it back “a bit every lap until I feel like I can stop without locking up.”

Bias is also a tire-temperature tool. Overheating the rears? Throw bias forward to take work off them. Can’t rotate the car? Bias rearward. In the rain, move it forward for stability — with less grip the rears lock and step out far more easily under braking.

Anti-roll bars — balance as the track changes

Most GT3, GTP, and prototype cars expose the front and rear anti-roll bars on cockpit controls. The rule is the same as in the garage: the end you stiffen loses grip. Stiffen the front bar for more stability and understeer; stiffen the rear to free the car and add rotation.

Live, ARBs do two jobs. First, they trim balance per section of a lap — most clearly on the Daytona and Le Mans road-oval layouts. A BMW GT3 driver described running a soft front bar (1) on the banked straights and a stiffer one (4) through the infield: the soft bar on the banking lets the car follow the surface and keep both fronts loaded, while the stiffer bar in the slow infield sharpens turn-in. Second, ARBs let you adapt as the track rubbers in over a long race and the car gains grip you did not have in qualifying.

On doing this corner by corner, the honest consensus is that a few of the very fastest drivers do, but most do not, and several said the fiddling cost them more than it gained. Adjust when you feel a problem, not on a schedule.

Traction control and ABS levels

On cars that model real electronics — GT3, GTP, the hybrid prototypes — traction control and ABS are themselves adjustable, usually on rotary switches. These are not the sim’s assists for new drivers; they are the car’s own systems, and you tune them to conditions and tire state. The general rule from quick drivers is to run TC as low as you can comfortably control, because every bit of intervention costs exit drive. A typical GT3 dry range is around 2 to 4, two or three clicks higher in the wet, and a click up late in a stint to preserve a fading rear tire at a small pace cost. There is plenty of disagreement — TC settings differ by car, track, and even corner, so treat any number as a starting point. ABS in ACC is famously left near 2 or 3 on most cars and rarely touched, as community setup discussions bear out. iRacing’s driving aids support article lists how it treats the broader set of assists.

Engine maps, fuel mix, and hybrid deployment

Many cars give you an engine or throttle map on a rotary. The two everyday uses are fuel saving (a leaner map trades a little power for lower consumption — see race strategy) and an overtake/attack map for a short burst of extra performance. On a long fuel-save stint, a leaner map plus lift-and-coast does most of the work.

Hybrid prototypes are their own case. iRacing’s GTP and the Ferrari 499P deploy electric energy automatically, and for most of their life there was nothing to adjust — drivers were told to brake and accelerate as if the car were a non-hybrid, as iRacerHUB’s hybrid guide lays out. That is changing: iRacing’s development updates describe redeveloping the GTP and 499P hybrid systems so the class blends engine and electric power to match the allowed output at all times, with multiple output levels on the 499P. As that work lands, what is automatic versus driver-controlled is in flux, so check your car’s control list each season.

Ovals: the weight jacker

Oval cars add the weight jacker, an in-car control that raises or lowers the right-rear corner to change cross-weight, or “wedge.” More wedge tightens the car (less rotation); less wedge loosens it. You use it to chase the balance as fuel burns and the track changes through a green-flag run, then adjust around traffic and the long left-hand load of the corners. iRacing’s Commodore’s Garage on crossweight explains the geometry. Note that the weight jacker is a fixed-setup and oval staple — the Dallara Indy NXT, for instance, has none on the real car, so iRacing does not give it one there.

Reading the car: the black box and your controls

You cannot adjust what you cannot see. iRacing’s black boxes show live data — F2 for the relative, F3 for standings, F4 for fuel by default — and your current brake bias flashes on screen when you change it. The faster you can read fuel-remaining, lap times, and tire wear at a glance, the better your live calls.

Bind these controls so you never take a hand off the wheel. A button box with rotaries for bias, ARBs, TC, and fuel map turns a fumble into a flick, and a load-cell pedal keeps your braking force repeatable so the bias you dialed in stays honest. For how the live picture connects to your stint plan, see race strategy and tire wear in setup.