A good suspension need to damping right. It's mean absorb the shock.

For this there is a spring and a brake/damping system for this spring.

A suspension that go back as quickly as it go down don't have a good damping system.
A suspension does not go in abutment on a big shock. They control by using a plastic collar on the tube.

The travel must be separate into 3 steps :
First when you go up on the bike ready to ride.
Second when you take a big jump
Full travel when you take a extra big jump, that is to say something to death !

The safety rule is to keep the last third of the race for your safety, for the day when it should not happen. A bottoming of the suspension is in effect a fall assured.

For these steps, we must adapt the pre-load of the spring.
It will help adjust the first step of the travel.

Take concrete examples:
- You up on the bike and the suspension go down 40% -> You have to put shims around 7/8mm on the fork springs or more loaded the rear spring damper.
- Your suspension will have 90% of his travel on current jumps -> Need to increase the stiffness of the springs. Either by changing either the shortening. -10% decreases in length give +10% its stiffness!

There are limits, as I indicate what values that you can do on any suspensions.

Now talking about the damping system. Those are hydraulic. Need to slow movement of parts in managing a transition from oil through holes sizes.
If there is not enough damping force will be able to increase the viscosity of the oil. Originally, often an oil viscosity of 5W, we'll use a 7.5W in the forks.
You can make mixtures of different viscosities, we obtain the 7.5W taking half of 10W and 5W !

Regarding the adjustable forks, most forks permit only to adjust the go up way even if both button are in different colors. Some cheap copies have problems of design which gives a very bad feeling about the jumps and bumps. That is why all the forks that offer UPower were disassembled and tested by us.
See the comparative article on the forks that were dismantled with the strengths and weaknesses.