Please provide the following when creating the Ticket:

Game Version number: 1.021.169
Modded?: (No)

Issue Description:

I've done some vehicle physics testing and crunched some numbers to understand why the vehicle behaviour is still quite odd at times (though definitely a dramatic improvement over previous Arma titles). This will be a fairly long ticket and I appreciate that some creative interpretation has probably been added to increase playability and that Arma is not a racing sim, but I figure that some of the current vehicle issues can be fixed by looking into the way the current grip, momentum and torque calculations have been made.

So to start the main issues identified in my testing were:

1. Vehicle momentum values seem off, meaning that braking power can be simultaneously be too weak at max braking or too strong - possible affected by hidden braking assist that rubber bands brake pressure OR a linear load-grip coefficient
2. Tyre slip friction values seem off and different for front and rear wheels, also does not seem to be calculated as a rotational value longitudinally
3. Vehicle torque values are discordant with the tyre grip and momentum calculations leading to situations like Trucks and BTRs not able to ascend slight inclines or tackle simple obstacles like small rock formations

in more detail:

Vehicle momentum affects the way that the vehicles experience longitudinal grip, the key identifiers for these issues were:

• Vehicle brakes would not be able to stop vehicles that were rolling back on inclines when in neutral despite the gradient being low and the vehicles moving at maximum 3-4kph - occurs for both jeeps and trucks, especially prevalent when trying to ascend small obstacles like minor rock formations
• Cars and jeeps had a stopping distance of around 10-15 metres from max speed on wet tarmac (tested using Skoda 105L, Skoda 1203, UAZ and Armored Humvee) - a more realistic value for the stopping distance of a Skoda 105L at 100KPH would be around 70 metres on dry surfaces
• Trucks had a stopping distance of around 30 metres from max speed on wet tarmac (tested using Ural 4320) - a more realistic value for the stopping distance of a truck like this at 80kph would be around 85 metres on dry surfaces
• Vehicles all have an understeer tendency and will happily understeer, but will not oversteer

What is the issue here? I think it is most likely the culprit of a linear load/grip coefficient for the tyres or a hidden braking assist, or possibly a combination of the two. The reason I say this is that it does not make sense that a vehicle with brakes so powerful that it can stop in almost an instant from full speed is also unable to lock the wheels when on a slight incline when full pressure is applied.

This leads me to believe that some or all of the following must be true:

The load/grip coefficient is linear (almost certainly true)
There is no rotational slip simulation in Arma (likely true)
Longitudinal slip is coded to trigger when the handbrake is applied or on certain surfaces (likely true)
There is a hidden brake pressure assist (possibly true, definitely true if there is actually rotational slip simulation)

What are the fixes? Any, all or some combination of the following:

A logarithmic load/grip coefficient - in real life a tyre's grip increases logarithmically with load - i.e. a tyre experiences a rapid increase in grip with load (in either X, Y and Z axis) this diminishes rapidly as the tyre approaches its peak friction, with this friction value decreasing once the tyre experiences slip. This would explain why vehicles left in neutral with the handbrake on can slide down hills if the game does not switch to the stationary physics model in time, because it has not calculated load longitudinally and has a static value horizontally.

Incorporation of a rotational slip mechanic - at the moment the game only seems to interpret slip as a force that can act on a static wheel or laterally, but slip should also be able to operate rotationally on a longitudinal axis given a logarithmic load/grip coefficient i.e. the vehicle should be able to exceed the peak friction of the tyres and spin the wheels using engine power under certain circumstances, for example flooring it and dropping the clutch in the Skoda 105L on a wet, grassy uphill should make the rear wheels spin, instead of bogging down the engine as is the currect behaviour. This would also fix the behaviour of the vehicles not slipping backwards in forward gears, or forwards in reverse gears.

Removal of a hidden brake pressure assist (ABS) - This is one I'm not 100% sure on, but would be the other possible explanation if I'm wrong about the other two. Essentially, it appears that there's a hidden ABS assist somewhere (if it's the case that the brake pressure calculation is simply incorrect due to the friction coefficient stuff discussed earlier), none of the vehicles represented in game would have ABS in real life, but in Reforger slamming the brakes on most vehicles from top speed does not result in the front wheels locking as they should, except sometimes on dirt roads where perhaps this is programmed to deactivate due ot the surface type.