New sim code

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Can you run just the tire contact part of your new sim at a higher frequency?

Also, I wonder if there are ways to speed it up by using the GPU...

Maybe something like:
1. bullet rigid body collision/physics step 90Hz
2. suspension response step 90Hz (no contact friction)
3. calculate impulse delta since last step (like in the old sim code)
4. solve driveline and tire contacts at 900Hz, feed impulse delta / 10 as external impulse (like in the old sim code)

Driveline and contact constraints are operating in velocity space, so it might work and should save quite a few body + wheels transform updates and wheel ray interpolation.

The issue I see atm is the separation of suspension response and contact friction. Think of car body roll due to contact friction. There would be a delay by one step(90Hz) till the suspension "notices" the friction effects. But then car mass/inertia might help here. I need to compare it to a full 900Hz version.