OBERSON BUYING GUIDE
How to adjust your mountain bike suspension
Oberson experts explain how to adjust sag, progression, and rebound to optimize the comfort, grip, and control of your mountain bike's suspension.
IN BRIEF
A properly adjusted suspension improves your bike's performance and increases your confidence on the trails. This guide explains how to set sag, check progression, and adjust rebound. A few minutes are all it takes to transform your bike's behavior and make every ride more enjoyable. If you ride a front-suspension-only mountain bike (hardtail), simply follow the instructions for the fork and ignore the sections concerning the rear shock.
Get your bike ready
Here’s what you need to do before adjusting your suspension:
Wear your usual cycling gear, including your helmet, hydration pack, and any other equipment you normally carry.
Inflate your tires to your usual pressure.
Disable all suspension lockout systems.
Find a flat, clear space, away from traffic.
Have a suspension pump and a measuring tape handy, if needed.
Consult the settings recommended by the manufacturer of your suspension or bike, if available.
Adjust your sag
Sag is the amount the suspension compresses under the rider's weight when they are in their normal riding position on the bike. Adequate sag allows your bike to absorb impacts while maintaining good traction.
Generally, aim for about 20% sag in the fork and 30% in the rear shock. However, these values vary depending on the suspension design and riding style. Consult your suspension manufacturer's recommendations.
Before taking a measurement, compress the fork and shock several times, then allow them to stabilize for a few seconds. This allows the suspension to return to its normal operating position and obtain a more accurate sag measurement.
Start with the rear shock, then move to the fork.
Rear Shock
1. Place the O-ring against the shock body.
2. Make sure the shock is fully open.
3. Carefully sit on the bike in your normal riding position.
4. Lift your feet off the ground so that all your weight is supported by the bike.
5. Carefully dismount the bike without moving the O-ring.
6. Check the O-ring's position relative to the sag percentages indicated on the shock or its shaft. If these markers are not present, measure the sag and compare it to the manufacturer's recommendations.
7. Add or remove air as needed.
After each pressure adjustment, compress the shock several times before re-measuring the sag. Repeat until the desired setting is achieved.
As mentioned previously, most riders should measure rear shock sag in a seated position. However, more aggressive riders may prefer to perform this check in a standing position, as this more closely reflects their position on the trails. If you choose this method, ask someone to hold the bike.
Fork
Many manufacturers provide air pressure recommendations based on rider weight. You can use these values as a starting point, then check the adjustment by measuring the sag. If the manufacturer does not provide recommendations based on weight or sag percentage, simply follow the procedure below.
1. Place the O-ring against the fork seal.
2. Make sure the front suspension is not locked out.
3. Stand on the pedals with your hands on the handlebars while riding slowly.
4. Allow the suspension to compress naturally under your weight without bouncing.
5. Gradually slow down and then carefully dismount the bike.
6. Measure the sag and compare it to the manufacturer's recommendations.
7. Add or remove air as needed.
As with the rear shock, compress the fork several times after each pressure adjustment before re-measuring the sag.
Riders who prioritize pedaling efficiency and support may prefer slightly less sag. Those seeking maximum traction and control on rough terrain may prefer slightly more sag. Start with the manufacturer's recommendations and make small adjustments as needed.
Check progress
Once sag has been set, it's time to check whether you're effectively using your suspension's travel.
Progression describes the increased resistance of the suspension as it approaches the end of its travel. Sag is related to rider weight, while progression is related to the forces applied to the bike. While sag determines how much the suspension compresses under your weight, progression influences its behavior when working deeper into its travel to absorb large impacts.
For an initial indication, slowly ride on a flat surface in a neutral standing position and compress the suspension as hard as possible without lifting off the ground. Test the fork and shock separately.
After each test, check the O-ring position. The closer it is to the end of the stanchion or shock shaft, the more travel you've used. During this test, the rear shock should use about 90% of its travel. The fork should use about 80-90% of its travel without bottoming out.
Next, ride on a trail you know well and re-check the O-rings. Your suspension should occasionally use most of its travel on large impacts without frequently bottoming out.
If your suspension regularly bottoms out despite adequate sag, you might need more progression. Conversely, if you're not using most of your suspension's travel, you might need less progression.
Progression is generally adjusted using volume spacers installed or removed inside the fork or shock. Adding a volume spacer makes the suspension more resistant to bottoming out at the end of its stroke. Removing one makes it easier to use the full travel.
If you are comfortable performing this type of maintenance, refer to the manufacturer's instructions for installing or removing volume spacers. Otherwise, a qualified bike shop can help you determine the right setting for your riding style and the terrain you frequent.
If you prefer not to install or remove volume spacers, a slight compromise on sag can be a practical solution. Adding a little air can reduce the risk of bottoming out, while removing a little can make it easier to use the full travel. However, keep in mind that this influences the entire suspension's operation, not just the end of the travel.
| What if... | Probable cause | Try this |
|---|---|---|
| Your suspension frequently bottoms out despite adequate sag. | Progress is insufficient. | Add a volume spacer. You can also add a small amount of air. |
| You're not using most of the travel despite adequate sag. | The progress is too significant. | Remove a volume spacer. You can also slightly reduce the air pressure. |
| Adding air prevents bottoming out, but makes the suspension too stiff. | The progress might be insufficient. | Consider adding a volume spacer rather than more air. |
| Reducing air pressure allows for more travel to be used, but the suspension becomes too soft. | The increase could be too large. | Consider removing a volume expander rather than reducing the pressure further. |
Adjust your bounce
Rebound damping controls the speed at which your suspension returns to its original position after being compressed. The goal is to allow the suspension to recover quickly enough to absorb a succession of impacts. If the rebound is too fast, the bike can feel nervous or bouncy. If it's too slow, the suspension won't recover quickly enough between impacts, which will reduce grip and control.
Rebound adjustment knobs are often identified by turtle and hare symbols or by + and - signs. In most cases, turning towards the turtle or the + sign increases rebound damping and slows down the return speed of the suspension. Conversely, turning towards the hare or the - sign reduces damping and speeds up the rebound. If in doubt, consult your suspension manufacturer's documentation.
Rear Shock
Turn the rebound knob to its slowest setting. Then, slowly drop off a curb while remaining seated on the bike. Gradually increase the rebound speed, one click at a time, then repeat the test.
The ideal setting generally corresponds to the fastest rebound that allows the shock to slightly exceed its sag position before settling.
Fork
Turn the rebound knob to its slowest setting. Standing over the bike, compress the fork about one-third of its travel, then quickly release it. Increase the rebound speed one click at a time, repeating the test until the front wheel barely leaves the ground. Then, turn it back one click.
Check overall balance
While riding slowly on a flat surface, repeatedly load and unload the suspension while standing. The fork and shock should feel balanced and return at a similar speed. If there is a slight imbalance, it's better for the fork to return slightly faster than the rear shock. Conversely, the rear of the bike can push the rider forward on large impacts. Once on the trails, make small adjustments as needed.
Troubleshooting common suspension problems
Even after following the steps above, you may want to fine-tune your suspension's behavior. Use the table below to identify the most common problems and possible solutions.
| What if... | Possible cause | Try this |
|---|---|---|
| Your fork or rear shock frequently bottoms out. | The spring rate or progression is insufficient. | Add a small amount of air. If the suspension feels too firm over small bumps, consider adding a volume spacer. |
| You're not using most of your suspension travel. | Spring rate or progression is too high. | Slightly reduce the air pressure. If you are still not using most of the travel, consider removing a volume spacer. |
| Your suspension feels too stiff over small bumps. | Air pressure or progression might be too high. | Slightly reduce the air pressure or consider removing a volume spacer. |
| Your forks dive excessively during braking or on steep descents. | The air pressure in the fork could be too low. | Add a small amount of air and try again. |
| The bike seems to bounce after impacts. | The bounce is too quick. | Increase rebound damping by turning towards the turtle or the + sign. |
| The suspension seems slow to return or doesn't recover quickly enough between impacts. | The bounce is too slow. | Reduce rebound damping by turning towards the hare or the − sign. |
| The bike feels unstable because the front and rear suspension react differently. | Rebound settings could be unbalanced. | Compare the front and rear rebound speeds and make small adjustments until the bike feels balanced. |
How to Adjust Your Bike Suspension at Home
FAQ — How to choose a mountain bike
What tools do you need to adjust mountain bike suspension?
You will need a shock pump. A tape measure can also be useful to check the sag on forks or shocks that do not display a sag percentage.
What do the turtle and rabbit symbols mean on a fork or shock?
These symbols indicate the rebound setting. Turning towards the turtle slows down the rebound speed. Turning towards the hare speeds it up. Slower rebound can improve control on large impacts, while faster rebound allows the suspension to recover more quickly between obstacles.
Why don't I use my suspension's full travel?
If you are not using most of your suspension travel on large impacts, the air pressure or progression may be too high.
Start by checking your sag. If it is within the manufacturer's recommended range, try slightly reducing the air pressure. If this allows you to use more travel, but the suspension becomes too soft, you might benefit from removing a volume spacer.
Keep in mind that it's normal to have a little unused travel left after most rides. The goal is to use most of the travel on big impacts without frequently bottoming out.
Why does my suspension feel too stiff on small bumps?
A suspension that feels too firm over roots, rocks, and small bumps likely has too much air pressure or too much progression.
Start by checking your sag. If it is within the recommended range, try slightly reducing the air pressure. If the suspension remains too firm and you aren't using most of the available travel, removing a volume spacer might be beneficial.
Can I use a regular bike pump to adjust mountain bike suspension?
No. Mountain bike forks and shocks operate at much higher pressures than tires, and a regular floor pump is not designed to accurately measure or deliver these pressures.
To properly adjust sag and air pressure, you will need a suspension pump. These pumps are specifically designed for this purpose and come with a pressure gauge allowing for precise adjustments.
Should I adjust the sag or the rebound first?
Start with sag. This dictates where your suspension sits in its travel when you are in your normal riding position. If your sag is wrong, it is difficult to assess other suspension adjustments.
Once sag is correctly set, move on to rebound. Rebound controls the speed at which the suspension returns after being compressed, and the ideal setting depends, among other things, on the air pressure and sag used.
The Oberson Repair Shop
Not sure if your suspension is properly adjusted? Our technicians can help you optimize your suspension settings so your bike can perform at its full potential. Visit us in Laval or Brossard to benefit from our expertise in bike maintenance and repair.
