Hello Shuo,
This is because, you have not defined the densities for the solids appropriately. Set the density of all the following solids to '8000 kg/(m^3)' so that it resembles steel.
- Cylinder (in the Shock absorber subsystem)
- Piston (in the Shock absorber subsystem)
- rim (in the Wheel subsystem)
You can find this parameter in the 'Inertia' dialogue:
Your tyre solid can remain at 1200 kg/(m^3) to resemble rubber if you want (the example model probably has an 8000 kg/(m^3) for that as well and could be considered a bug). In this case, my result looks as follows:
But if you want to replicate the exact same result as in the example, set the density of the tyre also to 8000 kg/(m^3).