You can adjust the mechanism inside the hinge to increase or decrease the speed.
How to adjust a door hinge spring.
Remove the locking pin.
Start by removing the locking pin photo 1.
Adjusting a spring loaded hinge must be done with the door closed.
Then add or release tension until you get the proper close rate photo 2.
If the self closing door to your garage isn t closing hard enough to latch properly or the door slams shut you can adjust the spring hinge tension with a hex wrench and pliers.
If your hinge has a tension pin inserted into the side of the hinge you need to pull the pin from the hinge with needle nose pliers.
I ll bet that you never knew you could adjust a self closing door hing.