I recently bought a Carreras centos limited edition mountain bike. I want to find out how to make my suspension bouncier and I want to experience a MUCH more comfortable ride. I have tried fiddling around with the knobs that say preload on them but it isn't making the ride any different. I am quite small and I don't know whether that is affecting the suspensions bounciness. Please help.
Bouncyness* may not be the appropriate term for the behavior you need from your suspension.
Suspension has two main functions: Shock Absorbing and Dampening. Shock absorbing is what the fork does by compressing, allowing the wheel to travel upwards. In this process, kinetic energy from the shock is used to compress either a coil spring or an air spring. Once this has happened, this energy that is "stored" in the spring has to go somewhere, and this happens when the wheel is forced down again.
If no other mechanism is in action, this energy returns almost at the same speed as it was put in, so it would be transmitted to your hands through the handlebar, giving an unpleasant and dangerous ride. That's where Dampening comes in. Dampening is a mechanism that slows down the shock absorber's return, consuming the stored energy, usually transforming it into heat.
Most forks achieve dampening by having oil reservoirs, pistons and valves. The fork moves oil from one reservoir to the other (from one face of the piston's head to the other) and the flow of oil is partially obstructed by the valves. The oil gets heated a little bit as it is forced through the valves.
With this in mind, we can understand the two main adjustments that any decent fork should have. Preload and Rebound Speed.
Preload is HOW STIFF is the suspension, and it's related to how much force must be applied to compress it. More preload means you need more force (apply more weight) to compress the fork by a given distance or travel. Speed Rebound is HOW FAST the fork return to it's uncompressed size after absorbing a shock.
If you feel that it takes too much force to compress your fork, it means you have too much preload. You mention you are too small (not heavy enough) so it's likely you must turn the preload all the way to the side marked with a minus sign (-).
There is a process to calibrate a fork, and it needs a ruler and possibly an assistant. You must measure SAG. Sag is the amount of travel that the fork compresses by just applying your weight to the bike in riding position. The user manual for your fork model should contain a table indicating the appropriate sag range for your weight. Preload is adjusted to achieve the desired sag, the more preload, the less sag and vice versa.
Chances are you weight too little for that fork. If this is the case, there may be some options: Change the spring, or change the fork. Some fork manufacturers sell different springs for some of their fork models, precisely to suit too big or too small riders. Refer to the fork owner's manual, It should bear the information. If you don't have the manual, It may be available from the manufacturer's web site.
If the fork is not serviceable or a softer spring for it is not available, you can change the fork for another one that fits your weight or that can be adjusted accordingly. An AIR fork may suit perfectly, since the "preload" of an air fork is given by the pressure of the air in the chamber, which obviously can be lowered to zero.
There is no preload adjuster on an air fork, but there is a valve for adjusting air pressure. They often require a specialized pump to load the air chamber and calibrate it. If you have a local bike shop near you they should be capable of swapping the forks and calibrate the new one.
You must also take into account that you have a front suspension only bike, so you will feel almost zero suspension effect for shocks to the rear wheel, so depending on the terrain you ride, you must learn to act as a suspension for yourself. It also depends on the purpose of your ride: sport, leisure, commuting... as this allows you to choose routes accordingly.
A limited option is to use lower tire air pressure, but not to low. Too low pressure may result in a bike that is not very maneuverable and prone to "snake bite" flats.
*A bouncy suspension can be understood as a faulty one, it is a suspension with no dampening or rebound control. It does not absorb the shock, it just stores its energy for a very little while and then returns it. For example, a car without dampener keeps going up and down after hitting a road bump, or you see its tires bouncing like a basket ball after a pot hole. A suspension with this condition is risky because it allows the tire to loose contact with road, leading to loss of control of the vehicle/bike
If you haven't done, so try playing with the tire pressures. Many riders assume that you need to inflate them to the maximum psi on the tire. If the pressure is too high the tires tend to bounce off of obstacles instead of rolling over them. If you are light enough, say less than 150 pounds you might be able to run the pressures at 25 or so psi. Set the front forks up with the lightest amount of dampening possible. By straddling the bike and applying the front brake you can push down on the bars and see how much travel you create. Make some adjustments and see if the amount the front end dips increases or decreases. Unless you are doing some aggressive drops try to use 2/3 of the travel. That will leave 1/3 to prevent bottoming out.
I believe that bike comes with an entry level Suntour fork. Honestly, there's not a whole lot you're going to be able to do with it to make it "bouncier", especially if you're a lighter rider. If you've turned up the preload, turn it all the way back down. Turning up the preload is only going to make the fork stiffer.