Two wheels can not be balance
I remember reading somewhere that physicists still don’t fully understand how a bicycle balances.
I found a link: https://www.newstatesman.com/science/2013/08/we-still-don’t-really-know-how-bicycles-work
Apparently it is not the gyroscopic aspect of the wheels that keeps a bicycle balanced.
I think the WheelColliders are more to do with tire friction and spring tension/dampening so they probably don’t offer much specifically for a bicycle seeing they usually have no springs and the frictional aspects of a bicycle tire are fairly insignificant. You would probably still use them though.
Something else to look into is the counter steering effect of a bicycle that most riders do without fully understanding why.
You may have to be creative here to emulate a similar balancing effect.