There have been a few posts about toe-in and toe-out on aircraft without really explaining the geometry of the spring type landing gear design. This does not apply to oleo strut, trailing link or bogie truck type gears.
With no weight on the wheels, a spring type gear has positive camber by design. This means the top of the tire centerline is tilted outward. Negative camber means the top of the tire is tilted inward.
As the aircraft enters a flare the pitch increases. With a pitch increase, the positive camber factors into two components, part positive camber and part toe-in. When the weight of the aircraft settles on the gear, the gear spreads. The spreading changes the positive camber into negative camber. This transition is more pronounced at higher weights. As long as the aircraft attitude is nose up with weight on wheels, the now negative camber factors into two components… part negative camber and part toe-out.
This transition from positive camber to negative camber, and toe-in to toe-out occurs on both conventional gear and tricycle gear.
If the aircraft has conventional gear, and negative camber with weight on main wheels and tailwheel, it will always have toe-out in the three point attitude.
However, if the aircraft is tricycle, the nose lowers after touchdown. This causes the toe-out effect of negative camber to transition back to near neutral toe-in while maintaining negative camber. ( There is a slight decrease in negative camber when some of the weight shifts to the nose gear.)
For tricycle gear aircraft, toe-in is stabilizing. As the aircraft turns, it leans against the outside tire. Because the CG is ahead of the tire the toe-in counteracts the turn much like a vertical stabilizer. Most tricycle gear aircraft are set up with slight toe-in with weight on all three gear.
For conventional gear aircraft, toe-in is unstable. As the aircraft turns it leans against the outside tire which is pointed into the turn. Because the CG is behind the landing gear the aircraft turns sharper and over-steers
Toe-out on a conventional gear is stabilizing. As the aircraft turns it leans against the outside tire which is pointing away from the turn. The tire angle decreases the turning tendency and directional stability is easily maintained by the pilot. . Most conventional gear aircraft are set up with slight negative camber with weight on wheels which results in a small toe-out component.
For an example of conventional gear toe-out stability one can look at aircraft equipped with “crosswind” landing gear. If too much pressure was put on the outside tire, the entire wheel simply casters to an extreme toe-out condition and removes any turning tendency.
If your aircraft is a bit squirrelly on landing, you might check the camber and toe angles with the aircraft loaded to the normal operating weight. If the gear is too stiff or bungees are too tight the gear may not be settling into the preferred negative camber position.
In summary, tricycle gear --- neutral or slight toe-in is best. Convention gear --- neutral to slightly toe-out is best.
I hope this clarifies the differences between conventional and tricycle landing gears and how they react with camber, toe-in and toe-out.
JP