The key to keeping hubcaps on a car is the retaining clips on the back. Hubcaps with metal retaining clips can be “stretched” out slightly towards the edge of the wheel. This will tighten the hubcap within the wheel and keep it on much better. This should be done every time the hubcaps are removed. Hubcaps with plastic clips will only stay on if all the clips are intact. There is generally no way to adjust this type. The best way to keep them on is to use care when installing them, not to break or bend back the plastic clips. This is how 90% of the plastic covers are lost.