How to Set Up a Rear Shock: SAG, Pressure & Rebound

MTB rear shock setup guide

How to Set Up a Rear Shock on a Mountain Bike

Set air pressure or coil spring rate, SAG, rebound and compression in the correct order—then fine-tune the rear of your bike with repeatable trail testing.

Quick answer

To set up an MTB rear shock, first check rear tire pressure and the basic condition of the shock and frame bearings. Identify the exact shock, stroke and bike model, then use the bike or shock manufacturer’s recommendation as the safest starting point. Set air pressure or coil spring rate, equalize the air chamber where required, measure SAG with your normal riding equipment, set rebound from a documented baseline, and adjust compression only after the spring setup is close. Test one change at a time on the same trail section. Use volume spacers only when the basic pressure, SAG and damping are already working.

Go to the detailed setup steps

Why rear-shock setup matters

Your rear shock affects traction, climbing efficiency, cornering support, braking stability, comfort and how confidently the bike uses its travel. A useful setup allows the rear wheel to follow the ground while keeping enough support for pumping, braking, compressions and landings.

The aim is not to copy another rider’s PSI or click count. The aim is to create a safe baseline for your exact bike and shock, test it consistently and adjust it until the rear suspension feels predictable on your terrain.

What can be adjusted on an MTB rear shock?

Not every shock has every adjustment. A simple air shock may offer pressure, rebound and a climb lever. More advanced air and coil shocks can include low-speed compression, high-speed compression, separate high- and low-speed rebound, volume spacers and hydraulic bottom-out control.

Setting	What it controls	Common symptom when incorrect
Air pressure or coil spring rate	The spring force supporting rider weight and holding the bike in its intended working range.	Too firm can reduce grip and travel use. Too soft can cause excessive squat, wallow or frequent bottom-outs.
SAG	The amount of shock stroke used under normal riding load.	Too little can feel tall and harsh. Too much can make the bike sit low, feel vague or lack support.
Rebound	How quickly the shock extends after being compressed.	Too fast can kick or bounce. Too slow can pack down through repeated impacts.
Low-speed compression	Resistance to slower damper-shaft movements caused by pedaling, pumping, cornering and weight shifts.	Too little can feel wallowy. Too much can reduce sensitivity and climbing or cornering traction.
High-speed compression	Resistance to fast damper-shaft movements from sharp hits, landings and hard compressions.	Too little can allow hard bottom-outs. Too much can feel harsh on square edges and rough terrain.
Climb or firm mode	Extra low-speed support for climbing or smooth pedaling, depending on the shock design.	Leaving it firm on rough descents can reduce traction and comfort.
Volume spacers	Air-spring progression deeper in the stroke on compatible air shocks.	Too many can block deep travel. Too few can allow easy bottom-outs even when SAG feels correct.
Hydraulic bottom-out	Extra damping support near the end of the stroke on shocks that include it.	Incorrect settings can affect deep-stroke support, but the function and range are model-specific.

Why rear-shock pressure cannot be predicted from rider weight alone

Rear-shock pressure depends on more than body weight. The frame’s leverage ratio, suspension layout, shock stroke, air-can design, shock tune, rider position, riding equipment and intended use all influence the required spring force. Two riders with the same weight can need very different pressures on different bikes.

Use PSI as a starting reference, not as the final answer. The bike manufacturer’s setup guide and measured SAG are more useful than a universal body-weight-to-PSI rule.

For a pressure-focused starting point, use the mountain bike shock pressure and SAG calculator. If the pressure reading changes when you reconnect your pump, read the MTB shock-pump guide.

The correct rear-shock setup order

Setup order matters. Rebound depends on spring force. Compression cannot correct a spring that is far too soft or too firm. Volume spacers should not be used to hide an incorrect pressure, spring rate or damping baseline.

Check rear tire pressure, shock condition and frame bearings.
Identify the exact bike, shock, shock stroke and available adjustments.
Set air pressure or coil spring rate from a reliable starting point.
Equalize the air spring where required and measure SAG.
Set rebound from a documented reference direction.
Set compression and climb mode according to the shock baseline.
Check front-to-rear balance and test one variable at a time.
Adjust volume spacers or bottom-out control only if needed.
Save the setup and record trail feedback.

For the complete bike-level process, see the correct MTB suspension setup order.

Step 1 – Check tire pressure, shock condition and frame movement

Rear tire pressure can imitate suspension problems. A tire that is too firm can make the rear feel harsh and skittish. A tire that is too soft can squirm, drag or make the bike feel vague. Start with a sensible tire baseline before judging the shock.

Quick inspection

Rear tire pressure is suitable for the tire, rim, rider and terrain.
Shock shaft and air can are clean.
No visible oil leakage around seals or adjusters.
Shock mounting bolts and hardware are secure.
Frame bearings move smoothly without unusual play.
No knocking, scraping, sucking or inconsistent damping.

Know when to stop tuning

Oil leakage, persistent air loss, excessive friction, damaged hardware, play in frame bearings or inconsistent damping may be service problems. Do not try to solve a mechanical fault with more pressure, more compression or a different rebound setting.

Step 2 – Identify the exact shock and bike

Record the bike model and model year, rear shock brand, model, generation, eye-to-eye size, shock stroke and whether the spring is air or coil. Also record the available damping controls and the direction from which clicks are counted.

The bike manufacturer’s guide is especially important for rear shocks because the frame leverage curve and original shock tune affect the correct baseline. Do not assume that settings from the same shock model on another frame will transfer directly.

Information worth saving

Bike, frame size and wheel configuration
Shock model, tune and stroke
Air-can or coil-spring configuration
Total riding weight with normal equipment
Manufacturer’s recommended SAG or pressure baseline
Click-counting direction for every adjuster

Step 3 – Set air pressure or coil spring rate

Air shock

Use total riding weight, including helmet, shoes, pack, water and tools. Start with the bike or shock manufacturer’s recommendation. Attach the shock pump carefully and adjust in controlled steps without exceeding the specified maximum pressure.

Many air shocks need to be cycled while they are being pressurized so the positive and negative chambers can equalize. Follow the procedure for your exact shock. Add pressure in stages, remove the pump before compressing the shock unless the manufacturer explicitly states otherwise, cycle the suspension slowly, then reconnect and recheck.

Connecting a pump increases the volume of the pressurized system and can make the gauge read lower than the pressure that was inside the shock before connection. A short hiss during removal usually comes mainly from the pump hose. Build a repeatable measurement method rather than repeatedly chasing the previous gauge number.

Coil shock

Select a spring rate that allows the bike to reach the manufacturer’s SAG target with an acceptable amount of preload. Preload is primarily used to remove free play and make a limited SAG adjustment; it should not be used to compensate for a spring that is fundamentally too soft.

Spring may be too soft when

SAG remains excessive after the allowed preload range.
The bike sits low and wallows in supportive terrain.
Bottom-outs occur too easily with sensible damping.

Spring may be too firm when

SAG is too low with only the required minimum preload.
The rear lacks grip or uses little travel.
The bike feels tall and harsh even with damping opened appropriately.

Step 4 – Measure and adjust rear-shock SAG

SAG is the amount of shock stroke used under normal riding load. Many trail and enduro bikes start somewhere around 25-33% rear-shock SAG, while some bikes or shock designs specify values closer to 30-35%. Always follow the target for your exact frame and shock when it is available.

Rear-shock SAG formula

SAG percentage = measured shock movement / shock stroke × 100

Example: a 65 mm stroke shock with 19.5 mm of O-ring movement has 19.5 / 65 × 100 = 30% SAG.

Rear-shock SAG calculator

Enter the shock stroke and measured O-ring movement. The optional target field shows how much shaft movement corresponds to your chosen target SAG.

Shock stroke (mm)

Measured SAG movement (mm)

Target SAG (%)

Enter the shock stroke and measured movement to calculate your SAG.

Important: use the shock’s actual stroke, not the bike’s rear-wheel travel. This calculator measures SAG; it does not replace the target supplied by the frame or shock manufacturer.

Repeatable measurement process

Wear your normal riding equipment, including pack and water.
Set the shock to its open or manufacturer-specified setup mode.
Equalize the air spring where required.
Slide the O-ring against the air can or shock body.
Get on the bike in a neutral standing riding position, ideally with a helper.
Avoid bouncing, braking hard or leaning against a wall with unusual body position.
Step off carefully and measure the O-ring movement.
Repeat the process to check consistency.

Measure shock stroke, not rear-wheel travel. A 160 mm rear-travel bike may use a 60 or 65 mm shock stroke. SAG percentage is calculated from shock-shaft movement divided by shock stroke.

Step 5 – Set rear-shock rebound

Rebound controls how quickly the shock extends after compression. More rebound damping generally means a slower return. Less rebound damping means a faster return. Start from the manufacturer baseline and record whether the number is counted from fully closed/slow or fully open/fast.

Higher air pressure or a firmer coil spring stores more return energy and may require more rebound damping. Recheck rebound after meaningful spring-force changes. Turn adjusters gently and never force them beyond their stops.

Possible too-fast rebound signs

The rear kicks upward after compressions or landings.
The bike feels bouncy or unsettled through rough corners.
The rear wheel skips instead of tracking the ground.
The bike pitches forward as the rear returns aggressively.

Possible too-slow rebound signs

The shock does not recover between repeated impacts.
The rear sits progressively lower through rough sections.
The bike feels dead, sluggish or harsh after several hits.
Travel is unavailable because the shock is packing down.

For a deeper explanation, read the MTB rebound guide.

Step 6 – Set compression and understand the climb switch

Some rear shocks have no external compression adjustment. Others have a simple open/firm lever, low-speed compression, separate high- and low-speed compression, or multiple pedal modes. Use the manufacturer’s recommended open, zero, middle or neutral starting position for the exact shock.

Low-speed and high-speed describe damper-shaft speed, not bicycle speed. Low-speed compression mainly affects pedaling, pumping, berms, braking and gradual weight shifts. High-speed compression mainly affects sharp rocks, square edges, hard landings and fast deep-stroke events.

Adding compression may help

The rear wallows in berms or compressions.
The bike lacks pumping or pedaling support.
The shock moves too easily under rider inputs despite correct SAG.

Reducing compression may help

The rear feels harsh or lacks grip.
The wheel deflects on roots and square edges.
The shock feels over-controlled despite correct spring setup.

Climb or firm mode

A climb switch increases support for smooth climbing on many shocks, but it is not a substitute for correct pressure, spring rate or low-speed compression. Return the shock to the recommended descending mode before rough terrain. Some shocks are not intended to be ridden fully locked on rough ground, so follow the manufacturer’s instructions.

For more detail, see the low-speed compression guide.

Step 7 – Test the rear shock and check bike balance

Choose a short familiar trail section containing a climb or acceleration, a supported corner, repeated bumps and one larger compression suitable for your riding level. Ride at a repeatable pace and use a similar line.

Record the complete baseline before the first run.
Change only one variable.
Use small changes: a few PSI, one or two clicks, or one documented adjustment.
Repeat the same section.
Decide whether the result is better, worse or unclear.
Restore the previous value when the result is worse.

Check front-to-rear balance

A correct rear setup can still feel wrong if the fork is mismatched. A rear end that is much softer than the fork can make the bike ride nose-high and push through turns. A rear end that is much firmer can make the fork feel overloaded and the bike feel nervous on steeps. Compare support, return speed and travel use at both ends.

Use the complete MTB fork setup guide to build a balanced baseline.

Step 8 – Decide whether volume spacers are needed

Volume spacers reduce the usable air volume and make a compatible air shock more progressive deeper in its stroke. They do not replace correct pressure, SAG or damping. Frame kinematics already create part of the overall progression, so a spacer change can feel different on different bikes.

Adding a spacer may help when

SAG and initial sensitivity are suitable.
The shock still bottoms too easily on hard impacts.
You want more end-stroke support without substantially increasing pressure.

Removing a spacer may help when

You cannot access deeper travel despite correct SAG and damping.
The shock ramps up too aggressively late in the stroke.
Harshness appears mainly near full travel.

Use only compatible spacers and follow the shock-specific service procedure and maximum spacer limit. Volume-spacer installation usually requires depressurizing and opening the air can; arrange professional service if you are not confident with the procedure.

For more context, read about linear versus progressive suspension tuning.

Temperature, pressure readings and setup consistency

Air pressure changes with temperature, and a shock can also warm during riding. Measure in a repeatable environment when comparing settings and do not overreact to a small pressure difference after transporting the bike from a warm room into cold weather.

Use the same shock pump, the same connection method and similar temperature conditions when possible. For a focused explanation, see how temperature affects MTB shock pressure.

Troubleshooting MTB rear-shock setup

Most handling symptoms have several possible causes. Use the table as a controlled first check, then change one setting at a time.

Symptom	Possible causes	First controlled check
Rear feels harsh on small bumps	High tire pressure, excessive spring force, too much compression, rebound packing, friction or service issue.	Check tire pressure, air-chamber equalization, SAG and shock movement before changing several adjusters.
Bike wallows or feels vague	Too much SAG, low pressure or soft coil, too little low-speed compression, or an unsupported frame/shock combination.	Recheck SAG, then test one small low-speed compression change if available.
Shock bottoms out too easily	Low spring force, too much SAG, insufficient compression support, too little progression or an unusually large impact.	Verify SAG and pressure or spring rate before considering compression or volume-spacer changes.
Shock does not use full travel	High spring force, too little SAG, too much compression, excessive progression, insufficient trail load or friction.	Verify actual shock stroke, SAG and compression baseline; full travel is not required on every ride.
Rear kicks upward or bucks	Rebound too fast, excessive spring force, or compression/rebound imbalance.	Add a small amount of rebound damping and repeat the same compression or landing.
Rear packs down in repeated hits	Rebound too slow, preventing the shock from recovering between impacts.	Reduce rebound damping in a small documented step and repeat the rough section.
Rear wheel lacks grip	High tire pressure, excessive spring force, too much compression, rebound too fast, bearing friction or poor weight balance.	Use one familiar corner or root section and test a single change that improves tracking.
Bike squats excessively while pedaling	Too much SAG, low spring force, too little low-speed compression or a naturally active suspension design.	Verify SAG, then compare the recommended open and pedal modes without using firm mode to hide a spring problem.
Pressure drops or feel changes repeatedly	Pump connection volume, temperature change, air leak, seal issue or inconsistent measuring method.	Use one repeatable pump process and inspect for persistent pressure loss over time.
Shock feels sticky, noisy or inconsistent	Contamination, dry seals, worn hardware, frame-bearing friction, air-spring fault, damper fault or overdue service.	Clean and inspect the system. If the problem remains, arrange professional inspection or service.

Common rear-shock setup mistakes

Using body weight without riding equipment.
Assuming rider weight directly equals a universal PSI value.
Ignoring the bike manufacturer’s SAG and setup recommendation.
Measuring SAG from rear-wheel travel instead of shock stroke.
Failing to equalize the air spring where required.
Using excessive coil preload instead of changing spring rate.
Changing pressure, rebound and compression at the same time.
Counting clicks from an undocumented direction.
Using the climb switch to hide a soft spring setup.
Adding volume spacers before checking pressure, SAG and damping.
Tuning on different trails or at different speeds every run.
Ignoring frame-bearing, hardware or service problems.
Forgetting to save the original baseline.

Interactive rear-shock setup checklist

The checklist works without an account and stores only local checkbox progress in your browser. If JavaScript is disabled, you can still use it as a static checklist.

FAQ

How much SAG should an MTB rear shock have?

Many trail and enduro bikes use approximately 25-33% as a starting range, while some frame or shock designs recommend values closer to 30-35%. Use the target for your exact bike and shock, then confirm the result on the trail.

How much air pressure should I put in my rear shock?

There is no universal rider-weight-to-PSI rule because frame leverage ratio, shock tune, stroke and air-can design all matter. Start with the bike or shock manufacturer’s recommendation, equalize the air spring where required and verify the result with measured SAG.

Should I measure rear-shock SAG from wheel travel or shock stroke?

Use shock stroke. Divide the measured O-ring movement on the shock shaft by the shock’s total stroke, then multiply by 100. Do not divide by the bike’s rear-wheel travel.

Why does my shock pump read less pressure when I reconnect it?

When connected, the pump hose and gauge become part of the pressurized system. Air moves into that extra volume, which can lower the displayed pressure. Use a repeatable measuring method rather than repeatedly chasing the previous reading.

How do I know whether rear rebound is too fast?

The rear may kick after compressions, feel bouncy, skip across rough ground or pitch the bike forward as the shock returns. Add rebound damping in a small recorded step and repeat the same trail feature.

How do I know whether rear rebound is too slow?

The shock may not recover between repeated hits, causing the bike to sit progressively lower, feel dead or become harsher as the section continues. Reduce rebound damping in a small step and retest.

Should I use the climb switch on every climb?

Use it according to the shock manufacturer’s instructions and your terrain. It can improve support on smooth climbs, but it should not compensate for incorrect pressure or spring rate. Return to the recommended descending mode before rough terrain.

Do volume spacers make a rear shock stiffer?

They mainly increase progression deeper in the stroke on compatible air shocks. They add end-stroke support but do not replace correct pressure, SAG or damping.

How much preload should a coil shock have?

Use the shock manufacturer’s minimum and maximum preload instructions. Preload should remove spring play and provide limited fine adjustment. If correct SAG cannot be reached within the allowed range, change the spring rate.

When does a rear shock need service instead of adjustment?

Persistent air loss, oil leakage, abnormal noise, sticky movement, damaged hardware, inconsistent damping or excessive play should be inspected. Adjustment is not a substitute for service or repair.

Turn your rear-shock baseline into a setup that improves after every ride

SAGLY helps riders find personalized starting values, save rear-shock settings, compare setup versions, document trail feedback, diagnose handling symptoms and change one variable at a time.

Keep pressure or spring rate, SAG, rebound, compression, volume-spacer notes and test feedback in one place instead of rebuilding your setup from memory.

Try SAGLY for MTB suspension setup

Building your complete setup? Follow the complete mountain bike suspension setup guide to set tire pressure, spring force, SAG, rebound and compression in the correct order.