The density is a factor so it is relative… setting a density of a part to 0.5 that weighs 500 versus a part that weighs 50 is very different. The parts wont equal the same weight if both of them are set to 0.5 density.
I believe the default density is set to 0.7 so if you raise it above this value to 1 for example it will increase the overall weight… if set below then it will make it lighter than it is.
That said, you generally want your aircraft light enough that the gears and wheels can take the weight but not flip over from being too light.
I was reading the post in more depth… the gif definitely helps, it doesnt seem like a weight issue… is the tyre noncollide right? Only the purple wheels are collide?
I’ve had this stupid glitch before too. Can you try making the base part where the tires connect to bigger? (Better if the actual base part is invisible and non-collidable)
It might also help if the base part is heavier too.
Not sure what really is the physics part of your landing gears, but let’s say part A is the base part, while part B is a cylindrical part, our tire. Part A should be scaled.