A suspension fork works best if it has been set up to accommodate the rider’s weight. When you sit on your bike, the amount the fork depresses, as the slider moves down the stanchion, is called the sag. As you ride, sag allows the fork to extend into the hollows in the ground, giving a smooth ride. To set the amount of sag, you can increase or decrease the amount of preload in the fork.
Damping controls the speed at which a fork works. To find out if a fork is working too fast, lean on the handlebar, then quickly lift up the front of the bike. If the suspension fork bangs back to its limit, its action is too quick and its rebound damping needs to be increased. Adjust the damping still further after a few rides. The best setup will let the fork absorb a hit and rebound quickly enough to be ready for the next.
Tools Needed:
- Shock pump
- Tie wrap
- Tape measure
Parts of a suspension fork
Crown; Stanchion; Slider; Fork brace; Brake boss; Steerer; Air valve; Dropout
Setting Sag
1. Put a tie-wrap around the stanchion of the unloaded fork and next to the top of the slider. Ideally, the sag should be about 25 percent of its available travel, though cross-country riders often prefer less and downhillers more.
2. Sit on the bike, wearing your normal cycling clothes.
- Place both feet on the pedals. Either ask someone to hold you upright on the bike, or lean your elbow against a wall. The slider will travel up the stanchion, pushing the tie-wrap with it.
3. Get off the bike and carefully measure the distance between the tie-wrap and the top of the slider.
- Express this measurement as a proportion of the fork’s available travel. If the distance is 1 inch (25mm) on a 3 1/5 inch (80mm) fork, the proportion is 32%. Check the owner’s manual to find out the available travel of your bicycle.
4. Increase the air in the chamber with a shock pump if the proportion of available travel is greater than 25%.
- Increase the spring preload with a coil/oil system (there is usually a dial at the top of the fork blade) or fit stronger springs.
- Release air, reduce the pre-load, or fit lighter springs if the proportion is less than 25%.
Fine-tuning the fork
1. Fine-tune the damping on some forks with an adjuster at the bottom of one of the fork blades. The two air chambers in this fork allow further refinements to damping.
- Pump air into the bottom chamber with a shock pump to change the spring characteristics.
- Change the size of a valve on the air piston to control air flow between chambers. This flow is called air-damping.
2. Make damping adjustments on some types of fork while riding the bike. The controls for these on-the—fly adjusters are usually marked faster” and “slower” to indicate which direction to turn them in. It is also possible to lock out some forks. This means that you can stop their action if you are riding over a very smooth surface and do not need suspension.