How to adjust your dirt bike suspension

How to adjust your dirt bike suspension

How to adjust your dirt bike suspension

Sit back, take a deep breath, and read this: your dirt bike's adjustable suspension is designed to be adjusted, and you can do it! Sure, suspension is a little more complex than adjusting chain tension or tire pressure, but with this guide and a few basic tools, you'll be able to handle all the essentials: setting sag, adjusting preload, rebound, and compression (where applicable), and understanding the basics of your dirt bike's suspension.

However, there are a few things to cover before we dive in.

Not all dirt bikes are created equal

This is an introductory article designed to help a wide range of riders on all types of dirt bikes, from late-model motocross bikes to motocrossers, vintage twin-shock enduros, and everything in between. Every bike will be a little different, and while there's no magic setting that works for every bike, you can make big improvements with a few simple adjustments. That's why we'll stick to the basics in this article. Don't worry if your bike doesn't look exactly like the examples in the pictures below.

Dirt bike suspension can (and will!) wear out.

Dirt bikes are incredibly durable machines that take tons of use and abuse. Their suspension systems require routine maintenance and service to function at their best, which means you can follow the entire suspension guide to the letter and still experience poor performance because the rear shock is blown, for example, or leaky fork seals are leaking all the oil. Check your suspension components, paying close attention to the seals. Seemingly unrelated maintenance items, such as chain tension, tire condition, steering head bearing health, and tie rod lubrication, should at least get a quick inspection before you start, as any of these can make your dirt bike feel like junk.

Check your owner's manual's maintenance schedule to make sure your bike is fully serviced before making any adjustments to avoid headaches.

Basic Suspension Tools for Dirt Bikes

Your motorcycle's manual should also describe the tools you'll need to work on your suspension, and if your bike came with a tool kit, now's the time to get it out. You'll need a variety of flathead screwdrivers, a hammer, a tape measure or ruler, a punch or impact wrench (often found in the tool kit), a dirt bike stand, and a notepad to record your changes as you go. If you decide to change the fork height, you'll also need some basic hand tools to loosen the triple clamp mounting bolts.

Basic dirt bike suspension terms

I'll introduce you to a suspension pro in a minute, but first, let's cover some basics and key suspension vocabulary. You'll want to know these words.

Travel — The length of the wheel's entire range of motion, from fully extended, without even the weight of the motorcycle on it, to fully compressed.

Sag — How much the suspension sags while the motorcycle is stationary. Free sag, also called static sag, is the measurement of sag without a rider on the motorcycle. Ride sag, also called active or rider sag, is the same measurement with a fully equipped rider on the bike.

Preload — Even on the simplest dirt bikes, preload adjusters change the tension on the rear shock spring(s), which affects sag. Preload alters the suspension's resting position in its travel. Increasing preload on the spring forces the bike to sit higher in the stroke, and decreasing preload allows the shock to sit lower in the stroke. The rear preload adjustment on almost all dirt bikes is located at the top of the rear shock spring, where you'll see threaded rings or a stepped collar. Fork preload adjusters are less common and are often located right in the center of the fork caps.

Damping — Hydraulic valves or gates that control the rate of suspension movement. (Not damping! This is when your bike gets wet.)

Compression, compression damping — Compression damping alters the rate at which the suspension compresses as you charge over bumps. Low-compression damping is soft and spongy, while high-compression is firm and sharp. You'll need a balance between the two. The rear compression adjustment is usually a small screw on the rear shock body, and the fork compression will be a small screw on the fork cap or inside the lugs. They often have markings around them so you can tell which way to turn. Typically, clockwise is tighter/firmer, and counterclockwise is looser/softer. To reset, turn inward (clockwise) until it stops and then count the clicks, or counterclockwise is outward.

Rebound, rebound damping — Rebound is the opposite of compression, as it controls the rate at which the suspension returns (rebounds) to its natural state. A primary function of rebound is to keep the tire on the ground. The rear rebound adjustment is typically a small screw on the fork or lower shock absorber where it connects to the linkage or swingarm. On forks, it's usually located on the fork cap or inside the lugs, just like compression. Typically, clockwise is tighter or firmer, and counterclockwise is looser or softer. To reset, turn inward (clockwise) until it stops and then count the clicks, or outward (counterclockwise).

Bottoming Out – The suspension has reached its bottom limit, and can't compress any further. You'll hear and feel it when it happens…

Topping out — The suspension has reached its limit. Topping out can make a “clang!” sound. Most new bikes have a top-end spring (TOS) to handle this, so a clang on a TOS-equipped bike could signal a problem; it's considered a wear item and can break. Frequent over- or under-travel indicates a suspension that isn't optimized for the rider or terrain.

Are you comfortable with those terms? Let's meet with our expert.

Brandon Fleming is the suspension manager at Solid Performance. While Solid specializes in KTMs and Husqvarnas, Brandon has helped countless riders get started with suspension tuning for their dirt bikes.

“I find that three out of four people at events don't even have their sag set correctly. They're usually off by about 20 percent,” says Brandon. “It's like the suspension is this mythical creature; no one wants to touch it. But you can run those screws all the way in, and nothing will break. So why not learn the basics and get the suspension close to where it should be?”

A simple sag adjustment will make a huge difference in your ride. Brandon's advice for novice suspension tuners? "Change one thing at a time," he says. "Take notes and you can always go back to what you had before."

If you do one thing in this article, set your sag . This puts your suspension in the optimal position, balancing the bike. Balance is the most important element of chassis setup, as it affects handling and bump absorption.

Things You Need to Know About Sag

There's a debate about whether to sit or stand while measuring a rider's sag, so I asked Brandon to weigh in. "When you ride, are you always sitting, especially when cornering?" he asks. "Or do you stand? We should all be standing all the time, but not everyone does. Be honest with yourself and accept how you ride. You can always readjust later."

Yes, your body weight is the same whether you're sitting or standing. However, sitting or standing shifts the weight distribution on the bike, which is why there's a difference. "Honestly, balance and sag matter whether you're sitting or standing," says Brandon. "It's important to be aware of the rider's feedback to sense if your balance is off and make adjustments on the fly, so be sure to bring your tools with you on the trail or road!"

Many riders set their sag when they first buy a bike and never adjust it again. Sag actually changes constantly based on temperature, spring rate, and how many cheeseburgers and beers you've had in the last week! We all know that metal expands and contracts with temperature, but riders don't realize that a change in temperature has any effect on sag and preload. Brandon finds that even a 10-degree difference can change your sag. Additionally, springs can eventually "take a set," meaning the overall length of the spring will change over time. You better believe that change affects sag.

In a perfect world, you'd check your sag before every ride, but that's not very practical without a fancy tool like Motool's Digital Sag Scale or a group of friends to help you out. Brandon recommends checking your sag at least once a season or every time you change the oil.

Setting the sag on a dirt bike

Start by placing your bike on a dirt bike stand so that the wheels are off the ground, fully reinforcing the suspension. Measure the distance from the axle block to a point directly above it on the bike's fender. Use the same point each time you measure. (Some riders cut a notch or draw a line to mark their spot. Newer KTMs have a "SAG" dot molded into the plastic.)

Got your size? Write it down and take the bike off the stand. Give it a few bounces to make sure it sits naturally, then measure again. (There's no rider on the bike yet.) The difference between measuring while standing and measuring on the ground is free sag, also called static sag.

Then the rider mounts. Get into the riding position! Hands on the bars, feet on the pegs. Stand up and sit down a few times to find your spot. Ask a friend to balance the bike (don't lean on the sidestand) and take the same measurement from the axle block to the fender, then subtract the resulting measurement from the measurement on the stand, i.e., the overall height. This is the rider's sag, also called racing sag.

“Rider sag is generally about a third of a stroke,” says Brandon. “So, if the travel is 240 mm, the rider sag should be about 80 mm.”

Maybe you find that your sag is already at the recommended setting in your manual, or right at the one-third mark. Sweet! You're done, move on to the fork section. For everyone else, it's time to bring the sag back into spec. Identify the preload adjustment on the rear shock absorber, which is almost always a collar above the spring. Tightening the adjustment compresses the spring and increases the preload, raising the bike's baseline. Loosening it will lower it. Now is the time to use the wrench or drift to turn the preload adjuster.

“Most preload collars have a locking ring of some kind,” says Brandon. “Yamaha has two metal ones. KTM has a nylon collar with a locking ring. They can be stubborn, and eventually someone will bang on that thing with a hammer and screwdriver. Here's a trick: Turn the spring by hand while turning the collar.”

Can't get the ring to turn anymore? Either your threads are dirty, or the shock is so full of preload that you need to switch to a stiffer spring. Keep adjusting until you reach that one-third goal. "It doesn't have to be scary," says Brandon. "They're crazy, imaginative things. Turn them!"

Roll the collars into their final position and you've just adjusted the sag. Nice!

Once you've set the rider sag, recheck the free sag measurement. The correlation between free sag and rider sag is how you identify whether you need a spring change. If you add too much preload to the spring, the system will be close to "bottom out" and will therefore not allow the frame to sag sufficiently under its own weight. Ideally, free sag should be 35 mm (+/- 5 mm) on modern full-height off-road bikes and a little less for models with less than 300 mm of travel.

Brandon relies on the XTrig preload adjuster for the easiest preload adjustments on newer bikes, and your favorite suspension shop can install one during a routine service. Brandon calls it the easy push-button preload and sag adjustment because there's only an eight-millimeter post to turn; no lockring, no hammer and screwdriver, and most importantly, no broken knuckles!

Pilot feedback

When the bike has excessive sag, often called "cut," the front tire is light or underloaded, and the rear tire is overloaded. This will make the bike slow to turn, causing the rider to typically experience upper arm and shoulder fatigue from fighting the front end. The front tire will also flex much more easily and may want to push or fade when cornering. 

When the bike doesn't have enough sag ("stink bug"), the front tire is overloaded and the rear tire is underloaded. This will make the bike turn quickly but will feel less stable at speed. This can make the bike want to lean or fall over in turns, and it can even feel like you're doing a pushup to keep yourself away from the front end. The rider may also experience fishtailing under hard acceleration and in a straight line. 

However, you can certainly control the front sag, which is typically 150 percent of the rear sag. (So if the rear sag was 80 mm, the front sag would be 120 mm.)

“WP/KTM/Pro Components doesn't list these numbers either,” Brandon adds. “It's more of a rider preference.” Front sag is measured just like rear sag, so you'll need to find a reference point. Brandon typically goes from the bottom of the axle nut to the bottom of the triple clamp or, if that's awkward, to the top of the triple clamp. Also, most forks don't have external preload adjustment, so fork preload is best left to intermediate and advanced tuners.  

Call a suspension shop if your front end sag is off, as you'll likely need a new set of springs. You can tweak your front end sag a bit by stiffening or loosening the compression damping (if equipped; more on that later), but if you're bottoming out or maxing out after experimenting with compression, you'll likely need different fork springs. Most people change their fork and shock springs at the same time to ensure proper bike balance.

Fork height adjustment

Fork height is a variable you can change on any dirt bike. Most riders don't think about how much of a difference fork height makes, but sliding the fork legs up or down in the triple clamps can have a serious impact on their handling. "Here's a great example," says Brandon. "We had an AA rider with pro components who was fiddling with settings but couldn't find the feel he wanted. In the end, it was the fork height adjustment that did the trick. He tried everything else and simply ignored it."

Lowering the fork in the triple clamp increases the bike's wheelbase, adding stability on straights at the expense of some maneuverability. Sliding the fork legs up through the triple clamp will make the bike turn tighter and faster, although it may feel weirder at speed.

With the sag set and the fork squared, it's time to tackle the compression and rebound, if your bike has these adjustments.

Compression and extension adjustment: the clicker exercise

Brandon and the rest of the Solid team recommend this clicker exercise to help riders get a feel for suspension settings. Start by setting the rebound and compression clickers to their factory default settings on both the forks and shock. Write down that setting and take the bike for a five-minute ride on your average terrain. When you return, write down how the bike felt. Did you like it? Was it stiff? Plush? Then, turn up the compression two clicks stiffer and the rebound one click stiffer on both the fork and shock.

Adjusting the fork and shock helps maintain the bike's balance. This rule of two compressions for one rebound scales the two adjustments quite well on most bikes, and in the same direction. Take the bike out for another five minutes on the same ride and note your impressions. Better? Worse? Add two more clicks of compression and one rebound and repeat until the additional changes feel worse, then return to the standard factory settings. Now use the rule of two to add compression and rebound in the opposite direction (out/softer). As you become more advanced with your adjustments, go back to adjusting only one thing at a time. The 2:1 rule primarily helps riders familiarize themselves with the range of "feel" the suspension has to offer.

Keep running laps and taking notes until the suspension becomes too harsh. Somewhere in your notes, there should be a “happy place” setting, or at least something tolerable. Set your bike to those settings and then start playing with a single click of rebound or compression to dial it in. From there, Brandon recommends focusing on the fork or shock independently, then the compression or rebound independently. 

Your dirt bike should be more comfortable and confidence-inspiring after a tune-up. That wasn't so bad, right? Your next steps in the world of suspension tuning will likely involve some interaction with a tuning shop like Solid Performance, but for now, you understand the basics of suspension tuning, and your bike is better optimized for your weight and riding style. That's a huge win.

You may find that your "happy place" setting is at the edge of your adjustment range, which means you'll want to talk to a tuner about new parts or a re-tuning. Think of your suspension like a suit. You can wear a suit that's out of the ordinary, but the look, feel, and fit are much better when that suit is tailored to you!

Symptoms and feedback

When you're new to suspension tuning, it can be difficult to describe your suspension feel or know what to try. Brandon has some tips for these riders. 

“We want you to use all your suspension,” says Brandon. “Bottoms happen. Riding all day, every day is a problem. That's why tuners install travel indicators on a fork, like an O-ring or a WP travel indicator. Don't use zip ties for this! They mark your chrome. If you're consistently bottoming out, regardless of your settings, you should talk to a shop. You want it to be compliant, but not blowing through the travel. Learning when to make which adjustment is not easy, which is why we go back to that clicker exercise.”

At first, it can be difficult to judge the feeling of sag. When you have excessive sag, the rear is too low compared to the front, and you might feel a slight shake in the corners from that light front wheel. With the opposite, too little sag in the rear, the front tire wants to grip too much. Instead of sliding or washing out, the bike wants to drop into the corners and feels like a pushup to turn. You might experience a bit of a side-to-side fishtail when going fast in a straight line. 

My bike has high and low speed settings. What's going on with that?

Brandon gets this question a lot. “People think it has to do with the speed of the bike,” he says. “No. It’s the speed of the suspension movement. Bumping, jumping, kicking are high speed. Bottoming, even hard hits. Low speed covers the rest. Just remember, it’s the speed of the suspension movement, not the bike itself.” Typically, the low-speed compression can be turned with a regular screwdriver and its movements are measured in clicks. The high-speed compression is usually a 17mm nut. Changes in high-speed compression are often measured in turns. You’d notice only a quarter turn.

What about air forks?

Some dirt bikes use air to suspend the fork. They have Schrader valves so the rider can adjust the air pressure. It's important to have the front end suspended (like on a stand) when checking the pressure, as the pressure will change depending on where the fork is set in its travel. For example, the standard pressure for a WP AER fork is around 10 bar (~145 psi), and when the fork bottoms out, the pressure can reach 70 bar (~1015 psi). 

Changing in 0,2 bar (~3 psi) increments is a good starting point. Many riders mistakenly think that air pressure controls stiffness and focus solely on air pressure without adjusting the fork's compression or rebound damping. As mentioned above, it's important to change one thing at a time. 

Try changing the air pressure in small increments without touching anything else. Then adjust the compression and rebound damping. If time allows, experiment with the clicker exercise at different air pressures to find the best match. Whether you're using air or coil forks, the spring rate and clicker settings together govern the feel of the bike.

If I like the way it drives, is there a wrong suspension setting? 

According to Brandon, no! But bad ones definitely exist. “We had a guy who loved his setup, but then he changed it to ride on different terrain, softening the compression by five clicks and stiffening the rebound by two clicks. He thought the bike “felt stiff” on the different terrain, so he went out and softened the compression, and tried increasing the rebound and making it stiffer to keep it from sagging. But it sucked! The problem he created is called packing, since the softer compression made it go lower in the stroke, and with this now stiffer one coming out of the stroke, it was simply staying down and the bike could never return to full height. If he had gone back to his base setting and followed the rule of one, he would have found something better, and from there he could make finer adjustments.”

“As a general rule, the faster you go, the stiffer your settings should be. When you slow down with your suspension set for a fast pace, it won't feel good, especially when you're fatigued, so that's where the clicker exercise starts to work. Be realistic with your riding. If it's a bad day for me, I'm leaning on the clickers on my bike and just getting the most out of the ride and how I feel.

What are the biggest mistakes motorcyclists make when adjusting their suspension?

“The biggest mistake I see is the ‘set it and forget it’ mentality,” Brandon explains. “Really, there are two types of bad riders I encounter. You have the Grade N types, who adjust everything all the time, and problems are never the rider’s fault… and then there’s the other type who sets the sag once and never touches it again. Become familiar with suspension adjustments, especially if you have air forks. Be aware of what the adjustments do so you don’t get frustrated or scared by the change and recognize how you’re performing that day.

Another problem I see is buying the wrong bike for the wrong application. People spend all this time adjusting the suspension on an inappropriate bike to handle what they actually want to do. Look, you can either waste a lot of money on it, or just admit you bought the wrong bike and trade it in.

Ignoring maintenance intervals is another mistake I see all the time. When a fork gets debris through its seals, the suspension degrades faster and faster. Most forks need to be serviced every 40-50 hours, and we're usually the ones who fix the big problems when people skip maintenance. We see a lot of worn parts, and sometimes entire components are burned out. Regular suspension maintenance not only leads to better ride quality, but also a lower cost of ownership when you factor in the potential expense of expensive internal parts broken from neglect. Linkages and swingarm bearings are also severely neglected. So keep up with your regular chassis with TLC, especially if you love your pressure washer.

I hope your bike feels better, you're used to turning the clickers, and your sag is right on target. Nice work! Our dirt bike suspension is meant to make your ride even better, after all, but it can't do that without a little know-how and attention. Have fun!

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