Tuning the suspension
Although there are a number of ways to tune suspension, we’ll focus on one of the most basic adjustments — controlling the amount of sag (the amount of movement in the suspension when you’re sitting on your saddle). The amount of recommended sag for most bikes is normally around 25 percent.
You can adjust the suspension much easier if you have a friend around to assist you.
To adjust the rear suspension sag, follow these steps:
1. For a coiled-spring-covered shock, determine the amount of travel (the total range that the suspension can move) by measuring the length of the coil when it’s fully extended, without any weight on the bike.
Suspension on the front forks usually has a greater travel than the rear suspension. Too much travel is not a good thing — it can damage your suspension by causing it to bottom out.
2. Sit on you bike while it’s stationary and don’t touch the ground with your feet.
Have your friend support you if needed.
3. Measure the length of the coil to determine the amount of sag.
4. Divide the measurement from Step 3 by the measurement from Step 1, to determine the percentage of sag.
For example, if the amount of travel was 4 inches and your sag was 1 inch, the percentage of sag is 1 ^ 4 = 0.25, or 25 percent.
If your sag is less than 25 percent, the suspension is too stiff. Proceed to Step 5.
If your sag is more than 30 percent, the suspension is too soft. Proceed to Step 6.
5. Adjust the spring tension in front by rotating the spring seat (as shown in Figure 12-7). To reduce tension and increase sag, turn the knob counterclockwise one turn.
Repeat steps 2 through 4 until the sag is between 25 percent and 30 percent.
6. Adjust the spring tension in front by rotating the spring seat (refer to Figure 12-7). To increase tension and reduce sag, turn the spring seat clockwise one turn.
Repeat steps 2 through 4 until the sag is between 25 percent and 30 percent.
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To adjust the front suspension sag, follow these steps:
1. Determine the total amount of travel by measuring from the top part of your forks to the seal of the forks or the lowest part of the shock that moves relative to the rest of the bike.
2. Sit on you bike while it’s stationary and don’t touch the ground with your feet.
Have your friend support you if needed.
3. Measure the distance between the two points again to determine the amount of sag.
4. Divide the measurement from Step 3 by the measurement from Step 1, to determine the percentage of sag.
For example, if the amount of travel was 4 inches and your sag was 1 inch, the percentage of sag is 1 * 4 = 0.25, or 25 percent.
If the sag was less than 25 percent, the forks are too stiff. Proceed to Step 5.
If the sage was more than 30 percent, the forks are too soft. Proceed to Step 6.
5. Adjust the spring tension in front by rotating your screw knob on the top of your fork (as shown in Figure 12-8). To reduce tension and increase sag, turn the knob counterclockwise one turn.
Repeat steps 2 through 4 until the sag is between 25 percent and 30 percent.
6. Adjust the spring tension in front by rotating your screw knob on the top of your fork (refer to Figure 12-8). To increase tension and reduce sag, turn the knob clockwise one turn.
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Repeat steps 2 through 4 until the sag is between 25 percent and 30 percent.
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Figure 12-8: Adjusting the front suspension |
If your friends have deserted you for the day, do the same process except use a zip tie around the fork instead of just eyeballing or measuring by hand. Use it to get the total travel and then reset it to get the sag. This gives you a more accurate measurement and is easier to perform.
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206 Part III: Shifting into a Higher Gear: Advanced Bike Repairs Maintaining the suspension |
How to maintain a bike’s suspension varies depending on the type of suspension. Suspension systems that use oil need more attention and maintenance than those that used coil-based springs. Follow your bike’s owner’s manual for how to maintain the suspension properly.
One of the most important things you can do for your suspension is to keep it clean. Disassemble your forks regularly and according to the recommended timeframe in the owner’s manual. (Figure 12-9 shows a disassembled suspension fork.) As a part of your annual overhaul, you’ll want to disassemble the forks and replace seals, wipers, and bushings.
Also, regularly inspect your bike’s suspension for signs of oil leaks. If you notice a leak, you should replace the seals as soon as possible.
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Figure 12-9: A disassembled suspension fork. |
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