A Major Overhaul of Car Physics: Tyres & Brakes

A quick update on the latest physics work, because this release includes the biggest physics overhaul I've worked on in a long time.

This update focuses on two major systems: tyres and brakes. And the differences aren't just cosmetic or small adjustments — we're talking about significant corrections to how the converted cars actually behave.

Tyres

I compared, curve by curve, what a converted car produces with what the exact same car produces in AC1.

This was done across 360 cars.

The biggest issue was longitudinal behaviour. The peak of braking grip was occurring at roughly half the slip ratio expected from the original mod.

This explains the premature wheel lock-ups that some of you have been reporting for weeks.

And no, 352% is not a typo.

The converted tyres were heating up and cooling down several times faster than they should have. In other words, you were driving on a tyre compound whose thermal behaviour was very different from the original mod.

Brakes

I used the same approach here: comparing the calculations from both engines and replaying them step by step.

Over eight hard laps, a converted car could differ from the original mod by 187 to 645°C, with braking force differences reaching up to 34% by the end of a stint.

This is now matched to the original calculations.

There was also a more subtle issue with brake temperatures.

The brake thermal model from the conversion skeleton could remain active when the original mod didn't provide one. Depending on the donor car used during the conversion, your converted car could therefore inherit a brake model that wasn't actually its own — or even end up without the correct one.

This has now been completely cleaned up.

What does this mean for you?

These changes are applied during the conversion process, not dynamically in-game.

So if you already have converted cars, they will still use the old physics.

You'll need to reconvert your cars to benefit from these improvements. That's the only thing you need to do.

And once you've reconverted them, I'd really like to hear what you think behind the wheel — especially under braking.

The measurements show that the converted physics now match the original much more closely.

Now I want to know if you can actually feel the difference.

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