Why do the values change when I add a car?

Because the reference is the slowest car on the grid. Add one slower than all the rest and it becomes the reference, so everyone else needs more slowing down.

If you are racing at a track we have data for, pick it: the order of the cars changes from one layout to another. If it is not listed, the average of all tracks is the best estimate we have.

Yes. Two drivers in the same model carry the same setting, so it is shown once per model.

Where do I enter these values?

In the Node Manager, on your server BOP screen. The dedicated server reads them at startup, so the room has to be restarted.

BOP calculator

Data measured on 2026-10-12 · 10 classes, 55 cars and 114 tracks measured

Pick a class, add the cars that will race and we tell you the ballast, power and drag that even them out. You can pin a specific track or keep the average of all of them.

ClassTrack

Your grid

Car 1
Car 2
Car 3

How it is calculated

The reference is the slowest car in YOUR grid: Not the slowest in the class. It keeps 0 ballast and 1.000 power, and everyone else is slowed down to it. That is why it changes when you add or remove a car.
Ballast first, power second: Ballast goes up to 5 % of the car weight; whatever is left is taken off power, up to 10 %. Slowing down beats speeding up: giving a slow car more power makes it hard to drive.
Drag shares out the straights: Taking power away also takes top speed away. Drag restores the straight-line balance without touching lap time further.

What this does not know

The cost of drag is not measured: We know what it does on the straight, not what it costs in lap time. It is the only unmeasured thing on this page.
A driver weighs more than a car: Two drivers in the same car at the same track differ by 14.7 % on average. That is why we only publish cars with at least three drivers and twelve laps.
This is one-lap pace: It does not include tyre wear, fuel use or drivability. A long race can order things differently.

Questions

Why do the values change when I add a car?: Because the reference is the slowest car on the grid. Add one slower than all the rest and it becomes the reference, so everyone else needs more slowing down.
Track or average?: If you are racing at a track we have data for, pick it: the order of the cars changes from one layout to another. If it is not listed, the average of all tracks is the best estimate we have.
Can I repeat a car?: Yes. Two drivers in the same model carry the same setting, so it is shown once per model.
Where do I enter these values?: In the Node Manager, on your server BOP screen. The dedicated server reads them at startup, so the room has to be restarted.