COMPLETE MTB SUSPENSION SETUP GUIDE: FORK & REAR SHOCK IN 20 MINUTES

Your mountain bike has somewhere between two and five thousand pounds' worth of suspension technology bolted to it. And if you haven't set it up properly, most of that engineering is working against you rather than for you.

Here's the uncomfortable truth: a properly set up hardtail will outperform a poorly set up full-suspension bike on almost every trail. Suspension that's too stiff doesn't absorb impacts. Suspension that's too soft wallows through corners and bobs on climbs. And suspension where the fork and shock aren't balanced makes the bike pitch and dive unpredictably.

The good news is that getting it right takes about 20 minutes. No special skills. No workshop. Just a shock pump, a measuring device, and a bit of patience. If you want a deep dive on the fork specifically, our MTB fork setup guide covers air pressure, rebound, and compression in more detail.

Why Suspension Setup Actually Matters

Suspension does three things: it keeps your tyres in contact with the ground, it absorbs impacts so your body doesn't have to, and it maintains the bike's geometry through rough terrain. When it's set up correctly, everything feels connected. The bike tracks where you point it. Braking is predictable. Corners hold grip.

When it's wrong, the symptoms are everywhere. Harsh hands and forearms on rocky descents usually mean the fork is too stiff. A bike that wallows and squats when you pedal hard means the rear shock is too soft. Diving under braking means the fork sag is too high. Getting bucked on successive hits means rebound is too fast.

The difference between a bike that inspires confidence and one that makes you hesitant is often just a few clicks and a handful of PSI. That's it.

Tools You Need

You can do this entire setup with three things:

Shock pump -- This is non-negotiable. A regular floor pump will destroy your air spring seals and can't achieve the pressures a rear shock needs. Shock pumps have low-volume, high-pressure chambers and a no-leak valve. If you don't own one, buy one before you do anything else. They're about 25 quid and worth every penny.

Measuring tape or ruler -- You need to measure your fork stanchion and rear shock stroke to calculate sag. A simple tape measure works. Some riders use a cable tie on the fork stanchion as a makeshift sag indicator -- this works in a pinch but a proper measurement is better.

The o-ring on your fork -- Most modern forks come with a rubber o-ring on the stanchion. This slides up as the fork compresses and stays in place, showing you how much travel you've used. If yours has fallen off or gone missing, a small rubber band works as a replacement. Your rear shock should have one too.

That's it. No torque wrenches, no bleed kits, no special stands.

Step 1: Set Your Air Pressure Baseline

Air pressure is the foundation of everything else. Get this wrong and no amount of clicking dials will fix it.

For the rear shock, start with a PSI roughly equal to your body weight in pounds. If you weigh 75kg (165 lbs), start at about 165 PSI. This is a ballpark -- every shock design and linkage ratio is different -- but it gets you in the right postcode.

For the fork, run lower pressure than the shock. A good starting point is about 55-65% of your body weight in pounds. For our 75kg rider, that's roughly 90-105 PSI in the fork. Forks have a larger air volume than rear shocks, so they need less pressure to achieve the same sag percentage.

Attach the shock pump, add air slowly, and disconnect carefully. Every time you disconnect a shock pump, you lose a tiny amount of air. This is normal. Account for it by adding 5-10 PSI above your target and letting the disconnection bring it back down. After a few tries you'll know exactly how much your pump loses.

Use our Shock Pressure Calculator to get a personalised starting point based on your weight and shock model.

Step 2: Setting Sag

Sag is how much your suspension compresses under your body weight when you're just sitting on the bike in riding position. It's expressed as a percentage of total travel.

Target sag by riding style:

| Style | Fork Sag | Rear Shock Sag | |---|---|---| | XC / Marathon | 20-25% | 20-25% | | Trail | 25-30% | 25-30% | | Enduro / Aggressive | 28-33% | 28-33% | | DH / Bike Park | 30-35% | 30-35% |

How to measure it:

1. Push the o-ring down against the seal on both the fork stanchion and rear shock
2. Get on the bike in full riding kit (helmet, pack, whatever you normally carry)
3. Have a friend hold you upright, or lean against a wall
4. Assume your natural riding position -- don't stand rigidly, just be relaxed with your weight where it normally sits
5. Carefully dismount without compressing the suspension further
6. Measure the gap between the o-ring and the seal

Divide that measurement by the total travel. If your fork has 150mm of travel and the o-ring moved 40mm, that's 27% sag. Right in the trail sweet spot.

If sag is too high, add air in 5 PSI increments. Too low, release 5 PSI at a time. Re-check after every adjustment. This is the part that takes the most time, but it's the most important step.

Step 3: Rebound -- The Drop Test

Rebound controls how fast the suspension extends after being compressed. Too fast and the bike bounces and bucks. Too slow and the suspension can't recover in time for the next hit, packing down into its travel until you're riding on the bumpers.

The drop test for the fork:

1. Stand next to your bike with both brakes on
2. Push down firmly on the handlebars, compressing the fork about a third of its travel
3. Let go and watch how the fork returns

If the front wheel bounces off the ground, rebound is too fast. Slow it down (turn the red dial clockwise on most forks). If the fork oozes back up sluggishly, rebound is too slow. Speed it up (turn anti-clockwise).

The goal: the fork returns to full extension as fast as possible without the wheel lifting. One smooth, controlled extension.

The drop test for the rear shock:

1. Stand over the bike with feet on the ground
2. Bounce your weight firmly through the pedals and saddle
3. Let the bike push you up and watch how it recovers

Same principle. The bike should return to sag point quickly and settle without oscillating. If your backside bounces off the saddle, slow it down. If the rear feels dead and unresponsive on consecutive bumps, speed it up.

A common mistake is running rebound too slow because it "feels plush." It might feel smooth on a single hit, but on a rough descent with rapid successive impacts, slow rebound means the shock can't extend between hits. The suspension stacks down, you lose travel, and the geometry steepens. Not what you want mid-descent.

Step 4: Compression Damping

Compression controls how the suspension behaves as it's being compressed -- the opposite of rebound. Most mid-range and higher forks and shocks have at least one compression adjustment. Higher-end units split this into two: low-speed compression (LSC) and high-speed compression (HSC).

Low-speed compression (LSC) controls the suspension's response to slow inputs: pedalling forces, body weight shifts, brake dive, and G-forces in berms. Adding LSC makes the bike feel more supportive and reduces bob on climbs. Too much makes the suspension feel harsh on small bumps and braking chatter.

High-speed compression (HSC) controls the response to fast, sharp impacts: rocks, roots, drops, hard landings. Adding HSC prevents the suspension from blowing through its travel on big hits. Too much makes the bike feel rigid and deflective on rough terrain.

Start with both wide open (fully anti-clockwise). Ride your normal trails. If the bike feels too soft and wallowy on climbs, add LSC two clicks at a time until the bob is controlled but the suspension still feels active on descents. If you're consistently using all your travel on drops or big hits but the bike feels fine otherwise, add a couple of clicks of HSC.

Most trail riders will end up with a few clicks of LSC and leave HSC wide open. Enduro riders might add some of both. The key is to adjust one thing at a time and ride between changes.

Step 5: Volume Spacers

Volume spacers (also called tokens or bottomless nuts) reduce the air volume inside the air spring. This doesn't change the beginning of the stroke -- your sag stays the same -- but it makes the suspension increasingly progressive as it moves deeper into the travel. Think of it as a ramp that gets steeper the further you compress.

When to add volume spacers:

• You're using all your travel regularly but the bike feels good otherwise
• You want more pop and liveliness without changing your air pressure
• Big hits or drops send you to full bottom-out even with correct HSC

When to remove volume spacers:

• The suspension feels harsh in the last third of travel
• You can never access your full travel even on big hits
• The bike feels dead and unsupportive deep in the stroke

Volume spacers require removing the air spring, so this is a slightly more involved job. Your fork and shock manuals will have instructions specific to your model. If you're not comfortable with it, any bike shop can do it in 10 minutes.

Start with one spacer at a time. The effect is noticeable but not dramatic. Most trail riders run 1-2 spacers in the fork and 0-1 in the shock. Heavier or more aggressive riders often run more.

Balancing Front and Rear

This is the part most people skip, and it's arguably the most important. Your fork and rear shock need to work together. If one is significantly stiffer than the other, the bike's geometry shifts dynamically as you ride.

Fork too stiff relative to shock: The bike pitches backward on impacts. The rear squats while the front stays high. You lose front-wheel grip on steep descents and the bike feels nervous under braking.

Fork too soft relative to shock: The bike pitches forward. The front dives under braking, the geometry steepens, and the bike feels twitchy and unpredictable on steep terrain. Climbing also suffers because weight shifts too far forward.

The simplest balance check: ride off a kerb or small drop at moderate speed. If the bike lands evenly on both wheels, you're balanced. If the front dips first or the rear squats excessively, adjust your sag percentages until the bike lands flat.

Both ends should reach full travel at roughly the same time on your hardest riding. If you're consistently bottoming the fork but have travel left in the shock (or vice versa), that imbalance needs addressing through air pressure, volume spacers, or compression settings.

When to Re-Check Your Setup

Suspension setup isn't a one-and-done job. Re-check your settings:

• Every season -- Air seals wear, damping oil degrades, and your riding style evolves. A spring check at the start of each season takes five minutes.
• After significant weight change -- Gained or lost 5kg? Your air pressures need updating. This includes the weight of your pack if you switch between day rides and bikepacking loads.
• When switching terrain -- If you normally ride flowy trail centres but you're heading to the Alps for a week of steep, rocky descents, consider adding 5-10 PSI and a click or two of HSC for the trip.
• After a fork or shock service -- Fresh oil and seals change how the damping feels. Re-do your rebound and compression settings after any service.
• When something feels off -- Trust your instincts. If the bike felt great last month and now feels vague or harsh, something has changed. Check your pressures first -- slow air leaks are common and a 20 PSI drop over a few weeks is not unusual on some shocks.

If you're not sure where your pressures should start, the Shock Pressure Calculator will give you a baseline based on your weight and setup. From there, follow the steps above and you'll have a bike that actually works the way it was designed to.

Don't forget tyre pressure — it works hand in hand with suspension, and getting both right makes a bigger difference than either one alone. And if you have a dropper post, our dropper post setup guide covers height, travel, and technique.

If you are riding through winter, consider running slightly softer spring rates and lower pressures for better traction on wet, slippery terrain. The same principles apply, but the conditions demand different settings.

Twenty minutes. That's all it takes. And the difference between a bike you tolerate and a bike you trust is usually hiding in those twenty minutes. The same is true on the road — a proper bike fit makes more difference than any component upgrade.