About RaceBoost

RaceBoost is a set of free tools that help sim racers drive faster in iRacing. Each tool answers one practical question with numbers you can copy using your own pedals and wheel, and shows how it got there.

How the Brake Planner works

Grip changes with speed. A car's braking grip is modelled as g0 + k × v²: a base grip from the tyres plus a part that grows with the square of speed, which is how downforce behaves. The planner shows k as “extra grip at 200 km/h”.

A corner is an arc. The corner angle becomes a radius by assuming the corner is an arc of a fixed length (100 m by default, adjustable). The fastest apex speed is the speed at which the car's grip exactly holds that radius.

Braking and cornering share the grip. Working backwards from the apex in 25 cm steps, the model uses all the grip left after cornering for braking (the friction circle). Cornering load builds from zero at the turn-in point, half the arc before the apex, to its full value at the apex. That is why the pedal trails off after turn-in.

Pedal percentage. 100% means threshold braking at the entry speed. Where the car has less grip than that, for example after the downforce fades, holding 100% would trigger ABS or lock a wheel. The planner shades that zone.

What it leaves out

• Brake bias, brake fade, tyre temperature and wear.
• How fast a real pedal can be pressed and released. The curve steps on and off instantly.
• Elevation, camber, kerbs and bumps. The track is flat and dry.
• Different grip for braking and cornering, and the car's weight transfer.
• Corners that tighten or open up. The radius is constant.

Treat the numbers as a starting point to test on track, not as the final answer.

Where car data comes from

iRacing does not publish its physics. Every car starts with an estimate, either for its class or for the car, and is labelled “Estimate” everywhere it appears. Estimates are replaced with measured values fitted from iRacing telemetry: straight-line stops at full pedal from several speeds, fitted to the grip model above.

Car and track names come from iRacing's public car and track lists. Facts such as power, weight and track lengths are added from iRacing's data service where available.

Not affiliated with iRacing

RaceBoost is not affiliated with iRacing.com Motorsport Simulations. iRacing is a trademark of its owner.