Your mountain bike's suspension can completely change how the bike feels on the trail. A poorly adjusted fork or rear shock can make an expensive bike feel harsh, vague, or difficult to control. Get the setup right, however, and the same bike can feel more planted, comfortable and predictable.
The good news is that you don't need to be a suspension expert to get started. Most riders can make a substantial improvement by working through four fundamentals: sag, rebound, compression and air-spring setup.
This guide explains what each adjustment does, how to set a useful baseline and how to fine-tune your suspension on the trail.
Why MTB suspension setup matters
Suspension has one fundamental job: keep the tyres in contact with the ground while controlling how the bike responds to bumps, braking, acceleration and changes in terrain.
Correct setup can improve:
- Traction on roots, rocks and loose surfaces
- Braking control
- Cornering confidence
- Comfort on long rides
- Resistance to harsh bottom-outs
- Pedalling efficiency
- Overall bike handling
Modern suspension systems offer a lot of adjustment, but more adjustment does not necessarily mean better performance. The key is changing one thing at a time and testing the result.
Step 1: Set your sag
Sag is the amount your suspension compresses under your weight while you're in your normal riding position.
It is the foundation of suspension setup. If sag is wrong, there is little point spending time fine-tuning rebound or compression.
As a general starting point, many trail riders begin around 20–25% sag at the fork and 25–30% at the rear shock. However, there is no universal number. Your bike, suspension design, riding style and discipline all matter.
How to measure sag
- Put on your normal riding equipment, including your helmet, shoes and riding pack.
- Set the suspension's compression controls to their open or recommended baseline position.
- Use a shock pump to set the air pressure according to the manufacturer's starting recommendation.
- Move the suspension through its travel a few times to equalise the air spring.
- Place the fork or shock's O-ring against its seal.
- Carefully get into your normal riding position.
- Step off without compressing the suspension further.
- Measure how far the O-ring has moved.
- Divide that distance by the available travel and convert it to a percentage.
For example, if a 160 mm fork compresses 40 mm under your riding weight:
40 ÷ 160 × 100 = 25% sag
Manufacturer recommendations should take priority over generic internet settings, particularly because different suspension designs can behave differently.
What if your sag is wrong?
If you have too much sag, the bike may feel soft and ride too deep into its travel. You may also experience excessive pedal bob or use too much travel during ordinary riding.
Adding air pressure reduces sag.
If you have too little sag, the bike can feel harsh and may struggle to respond to smaller bumps. Reducing air pressure increases sag.
Don't chase a particular percentage at the expense of how the bike actually rides. Sag is a starting point, not a magic number.
Step 2: Set rebound damping
Rebound controls how quickly the suspension extends after being compressed.
Too much rebound damping makes the suspension return slowly. This can cause the fork or shock to pack down through a series of bumps because it doesn't have enough time to recover between impacts.
Too little rebound damping makes the suspension return too quickly. The bike can feel nervous or springy, particularly after larger impacts.
Begin with Trail Tuner baseline settings and use a curb or controlled compression test before fine-tuning on the trail.
How to tune rebound on the trail
Find a familiar section containing repeated bumps.
If the suspension feels as though it gets progressively lower through consecutive impacts, try slightly faster rebound.
If the bike feels like it kicks back aggressively after impacts or becomes difficult to control, try slightly slower rebound.
Make adjustments one click at a time. Then repeat the same section.
This is much more useful than turning the dial several clicks and trying to remember what changed.
Step 3: Adjust compression damping
Compression damping controls how readily the suspension compresses when it encounters a load.
Depending on your suspension, you may have:
- Low-speed compression
- High-speed compression
- A simple open/firm adjustment
- A lockout or pedal-assist mode
The terminology can be confusing because low-speed and high-speed compression refer primarily to shaft velocity, not how fast you are riding.
Low-speed compression affects suspension movement caused by things such as braking, cornering and rider input.
High-speed compression becomes more relevant when the suspension shaft moves rapidly, such as during sharp impacts.
What happens if compression is too firm?
The bike may feel supportive but harsh. Small bumps can transmit more force to the rider, and the tyre may struggle to follow rough terrain.
What happens if compression is too soft?
The suspension may feel comfortable but lack support. You may experience excessive brake dive, pedal movement or frequent bottom-outs.
Start with the manufacturer's recommended baseline and make small changes from there.
Step 4: Check air pressure and volume
Air pressure determines the basic spring rate of an air-sprung fork or shock.
But pressure isn't the whole story.
Many modern suspension components use volume spacers or other methods of changing the air spring's progression. These alter how the suspension behaves deeper in its travel.
Adding volume spacers generally makes an air spring more progressive. That means the suspension becomes harder to compress toward the end of its travel.
This can help riders who are using full travel too easily or repeatedly bottoming out.
However, adding spacers isn't automatically the answer to every bottom-out problem. Incorrect sag, compression settings or riding technique can also contribute.
A simple MTB suspension setup sequence
If you're starting from scratch, don't adjust everything at once.
Use this order:
1. Air pressure → 2. Sag → 3. Rebound → 4. Compression → 5. Volume spacers
This approach gives you a repeatable baseline and makes it easier to understand what each adjustment is doing.
Several current suspension setup guides use the same basic principle: establish the spring setup first, then tune damping and finally make more advanced changes.
How to diagnose common suspension problems
My fork feels harsh
- First check sag and air pressure.
- If those are reasonable, try reducing excessive compression damping. Also consider whether your rebound is too slow.
- Don't immediately remove volume spacers. A harsh fork can have several causes.
My bike feels too soft
- Check sag first.
- If sag is correct, experiment with compression damping. If the bike feels fine through most of the travel but blows through the final part too easily, air-spring progression may be the issue.
My bike feels like a pogo stick
Rebound may be too fast.
Slow it down one click at a time and test again.
My suspension packs down in repeated bumps
- Rebound may be too slow.
- Increase rebound speed gradually and repeat the same section of trail.
I'm constantly bottoming out
- First check your sag and make sure you're using the correct air pressure.
- Then consider whether you need more progression from compression damping or an air-volume adjustment. Volume spacers can be useful when the basic spring setup is correct but the suspension still uses too much of its final travel.
The bike dives heavily under braking
- Check fork sag and compression settings.
- However, remember that braking technique and body position also influence how much the fork dives. Suspension adjustment cannot completely compensate for riding technique.
Should fork and shock settings match?
No.
The fork and rear shock perform different jobs and work with different parts of the bike's geometry.
You might therefore end up with apparently different settings front and rear.
The important thing is how the whole bike behaves, not whether the numbers look symmetrical.
Should you use the manufacturer's settings?
Absolutely—use them to cross check the first Trail tuner baseline.
Fox, RockShox, Öhlins and other manufacturers provide pressure charts, setup instructions and baseline settings for their suspension components.
Your final settings should then be adjusted according to your weight, riding style, terrain and preferences.
The best way to tune your suspension (Manual Adjustments)
The most effective suspension tuning method is surprisingly simple:
Change one thing. Ride the same section. Evaluate it. Repeat.
Pick a familiar trail with a mixture of braking, corners, bumps and repeated impacts.
Record your baseline settings in Trail Tuner. Then make a single adjustment—perhaps one click of rebound or compression.
Ride the same section again.
If the change makes the bike worse, return to the previous setting. If it helps, keep it and make another small adjustment. Trail Tuner keeps all your history and you can set any of these to a baseline.
This removes much of the guesswork from suspension tuning.
Final thoughts
You don't need to understand every suspension adjustment to make your mountain bike ride better.
Start with sag. Then set rebound. Establish a sensible compression baseline and only then start experimenting with more advanced changes such as air-volume spacers.
Most importantly, make small adjustments and test them on familiar terrain.
A properly tuned suspension system should not simply feel softer. It should give you more usable grip, better support and greater control.
And if your bike still doesn't feel right after careful setup, don't assume the suspension itself is the problem. Tyre pressure, tyre casing, geometry, riding position and technique can all have a major effect on how a mountain bike feels.
The goal isn't to find the settings that look best on paper. It's to find the settings that make your bike work best on your trails.
For a small once off fee per bike, use the Tuner AI feature to fine tune your suspension by describing what the bike is doing. This closes the gap between the numbers and what you are feeling.