hello
edit:
this thread has become so massive ill try to gather important posts here,
New answerhub post with test project download here
https://answers.unrealengine.com/questions/315371/wheeled-vehicle-physics-issues.html
demonstrates car launching into the air and stationary car refuses to move on impact
Issues still present:
The main issue still remaining
car launching into the air
Under investigation by Epic! UE-21990
video
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=183110&viewfull=1#post183110
PVD files of this issue
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=183738&viewfull=1#post183738
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=184760&viewfull=1#post184760
issue shown in Physx SDK
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=200808&viewfull=1#post200808
on Nvidia Developer Zone
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=202874&viewfull=1#post202874
same problem, same physics, different engine
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=271932&viewfull=1#post271932
old answerhub, unresolved!
https://answers.unrealengine.com/questions/125749/45-vehicle-strange-jump.html
Stationary vehicles refuse to move on impact
UE-21990
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=181845&viewfull=1#post181845
video
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=182101&viewfull=1#post182101
where the problem lies in the physx sdk
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=184466&viewfull=1#post184466
strange ‘Magnet’ effect
Under invesigation by Epic! UE-21941
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=312165&viewfull=1#post312165
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=316518&viewfull=1#post316518
Falling through the floor
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=355827&viewfull=1#post355827
character can ‘ping’ vehicles into space just by touching
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=368831&viewfull=1#post368831
Stuff thats been Fixed: 
video showing suspension rising and COM offset issues *Fixed
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=161849&viewfull=1#post161849
Wall Riding, possibly due to COM issue
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=162812&viewfull=1#post162812
Incorrect Drag calculations *Fixed
https://forums.unrealengine.com/showthread.php?48843-Horrible-Car-Physics&p=181786&viewfull=1#post181786
original post:
as the title says, the car physics are really quite terrible.
i recently played with the ‘advanced’ ahem… vehicle in 4.5 preview and was kind of expecting some improvement on the normal one.
sadly, its even worse, sure the suspension looks visually different but the physics is almost non existent. also ‘suspension force’ or whatever it was has gone from the wheel properties, so how do you get the car to lean? (edit: its in the wheel blueprints)
also why does the car raise up as it gets going faster?
has anybody found the cause of the mystery self up-righting?
i have started making my own vehicle using a physics asset with constraints but i cant get the wheels to spin any faster than about 10 mph.
anyone working on a decent car?
please Epic, whats going on with the physics?
are there any planned improvements or anything?
cheers