Steering system issues (wheels wobble and others)

After doing some research on how jbeams work, I believe that the current steering system that all the cars are using right now seems to be the problem to the strange reactions of the front wheels since the "pressurewheels" update. It was working fine with the hubwheels, but I think this needs to be addressed somehow.

Again, this happens to ALL the official cars (some more noticeable than others but it's there), just use slow motion to check it out. Wheels wobble under pressure, full throttle, burnouts or moving up and down.
It gets worst with mods, as changing even the smallest number on any of the suspension components can screw up the entire steering system (hydros and such).
Not to mention that the "pulling to one side" is a common issue too, on some cars is less noticeable but is there.

I've been trying to find a way around these problems, but I hit a wall every time I think I'm getting somewhere given that there are so many numbers to mess with related to the whole steering system.
Could be my lack of expertise in the jbeam department that prevents me to find a way to make a proper steering system or is there something that the devs should consider fixing somehow? maybe implementing a more simple way to make steering work?

Just thinking out loud.

 

Primarily this is a problem of the suspension/steering structure having too similar a natural frequency compared to the forcing frequency from the tires. To solve this one can either make the suspension/steering very stiff with low damping, or make the steering have low stiffness and lots of damping.

The tough part is that each vehicle has different tire options with different weights, sizes, and grip levels. Also, tires can spin at a big range of speeds which mean the forcing frequency varies. This makes it tough for a catch all solution when tuning the jbeams.

The problem has existed, and at times been much worse with the old wheel models, so its not the pressure code at fault. My latest tire and suspension tuning has brought some improvements to wheel shake in the official vehicles. There are also a few bugs in the drivetrain model that cause excess shaking, but we've made some very recent progress fixing those too

edit: One other thing to add. If you are having trouble with your mod pulling to the left or right, or both, check that the toe-in is fairly straight, and that the steering does not exhibit too much bump steer. This can be checked quickly by alternating gravity while looking down on the tire to see if the toe in changes as the suspension compresses.

 

Setting the steering to have more damping than spring fixes the wheels wobble thing. But there's something else here, what's causing the wheels toe to change so bad when under power, and with the suspension uncompressed? (suspension setup is based off your Toyota Sprinter).



This is the steering code with the softer / high damp beams:

Code:

{"beamPrecompression":1.0, "beamType":"|NORMAL", "beamLongBound":1, "beamShortBound":1},
            {"beamSpring":2501000,"beamDamp":2000,"beamDeform":165000,"beamStrength":185000},
            ["fh6r","fh6l"],
            //toe (below 1 = toe out, above 1 = toe in)
            {"beamPrecompression":1.01},
           [COLOR=#008000] {"beamSpring":501000,"beamDamp":5000},[/COLOR]
            ["fh3r","fh6r"],
            ["fh3l","fh6l"],
            [COLOR=#ff0000]//["fh5l","fh5r"],[/COLOR]

So far the only partial solution to this was to tie both fh5 nodes together, but that doesn't makes sense in real life, and it stiffens the front suspension a bit wich I don't like.

Been messing with different values but I can't seem to find what's causing this problem, wich the Sunburst has as well but is less noticeable.

 

501000 is way too soft. Spring values are in N/m, so that would be about 50kg/mm or only 10x the stiffness of the average car's coil spring.

One challenge is that drive/braking forces cause a forward/backward force on the tire contact patch, creating a torque acting about the steering axis. Happens in a real car too, but the steering arms are a lot stiffer and the scrub radius on fwd cars is usually very small or even slightly negative.

Another challenge is bump steer, which is a geometry consideration with the angle and length of the steering arm compared to the suspension arms. Also a consideration in a real car.

99% of the problems with making a car is that every force and behavior of a cars suspension and steering is simulated, even the inconvenient ones. There is no special code in the physics for what a steering beam is or what suspension is, and the physics engine is quite self consistent. All these problems are just a matter of dealing with geometry and stiffness/vibration in a similar way an automotive engineer would have to do in a real car.

 

If it's not that soft (the tie rods) then the wheels go crazy under acceleration. That's the only solution I could find for it.

If I make them stiffer, not only the wheels wobble a lot, but it doesn't solves the problem of the toe modification when the suspension is uncompressed.

Tried different scrub radius but they don't make any difference to this problem.

Changed the length of the tie rods but that didn't help either.

I'm no engineer... (but I have to admit I'm learning a lot about how suspension works)

 

Well, that actually did it. So the key to minimize that is to make sure that the lower arm and tie rod joints have the same x axis value, both inner and outer, so the beams have the same length.

Still I've had to use a lower spring rate and high damping for the tie rods to fix the straight line wobble (which might not be 100% accurate to the real thing) , otherwise under full acceleration on a straight surface, the wheels would wobble out of control.

 

I would shift both ends of the tie rod inwards an equal amount. so that you have ackerman steering. That shouldnt have any bad effect on bump steer.