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Common Tread

How to adjust your dirt bike suspension

Sep 17, 2020

Adjusting your dirt bike’s suspension can be a daunting task when you’re inexperienced. Especially modern bikes, bristling with fancy clickers and knobs, can be downright intimidating.

Take a seat, breathe deep, and read this: The adjustable suspension on your dirt bike is intended to be adjusted, and you can do it! Granted, suspension is a little more involved 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 your sag, adjusting preload, rebound and compression (where applicable), and understanding the basics of your dirt bike’s suspension. 

Kawasaki KLX jumping
Thrashing your dirt bike is fun! Just remember to keep up with your suspension's needs for the most performance and the least trouble from your shock and fork. Photo by Kevin Wing.

There are a few things to cover before we dig in, though.

Not all dirt bikes are the same

This is an introductory article meant to help a wide range of riders on all kinds of dirt bikes, from late-model XC bikes, to motocrossers, to twin-shock vintage enduros, and everything in between. Each bike will be a little different, and although there is no Magic Setting that works for all bikes, 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.

Lubricate dirt bike linkage with grease gun
When was the last time you lubricated your linkage? This bike uses grease fittings for easy maintenance. Photo by Andy Greaser.

Dirt bike suspension can (and will!) wear out

Dirt bikes are incredibly tough machines that take tons of use and abuse. Their suspension systems need routine maintenance and service to perform their best, which means you could follow this entire suspension guide to the letter and still have crummy performance because the rear shock is blown, for example, or because leaky fork seals let all your oil out. Check over your suspension components, paying careful attention around seals. Seemingly unrelated maintenance points, like chain tension, tire condition, steering head bearing health, and linkage lubrication, should at least get a quick inspection before you start, because any one of them can make your dirt bike feel like garbage.

Take a peek at your manual’s maintenance schedule to make sure your bike is all caught up before adjusting to avoid headaches.

Dirt bike suspension tools
You probably have everything you need already on hand: a dirt bike stand, a tape measure, and some way of turning your shock collars. Check your tool kit for a shock spanner, use a shock punch, or get medieval with a flathead screwdriver. You might need some basic hand tools, too. Photo by Andy Greaser.

Basic dirt bike suspension tools

Your bike’s manual should also describe the necessary tools for working on your suspension, and if the bike came with a tool kit, now’s the time to dig it out. You’ll want a variety of flathead screwdrivers, a hammer, a measuring tape or ruler, a shock punch or shock spanner (often found in the tool kit), a dirt bike stand, and a notepad to write down your changes as you go. Should you decide to change your fork height, you’ll also need some basic hand tools to loosen the triple tree pinch bolts.

Basic dirt bike suspension terms

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

Travel — Length of the wheel’s full range of motion, from fully extended, without even the bike’s weight on it, to fully compressed.

Sag — How far the suspension squats while the bike’s sitting still. Free sag, also called static sag, is the sag measurement without a rider on the bike. Race sag, also called active or rider sag, is the same measurement with a fully geared rider on the saddle.

Preload — On even the most basic 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 range of travel. Increasing preload on the spring forces the bike to sit higher in the stroke, and reducing preload lets the shock ride lower in the stroke. The rear preload adjustment on almost all dirt bikes can be found 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 they often sit right in the middle of your fork caps.

Damping — Hydraulic valves or gates that control how quickly the suspension moves. (Not dampening! That’s when your bike gets wet.)

Compression, compression damping — Compression damping alters how quickly the suspension compresses as it loads up on bumps. Low compression damping feels soft and spongy, while high compression feels stiff and sharp. You’ll want a balance between the two. Rear compression adjustment is usually a small screw on the rear shock body, and 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/stiffer and counter-clockwise is looser/softer. To reset, turn in (clockwise) until it stops and then count clicks or, turns out, counter-clockwise.

Rebound, rebound damping — Rebound is the opposite of compression, in that it controls how quickly the suspension returns (rebounds) to its natural state. A primary function of rebound is keeping your wheel on the ground. Rear rebound adjustment is typically a small screw on the clevis or bottom part of the shock where it connects to the linkage or swing arm. On the forks, it is usually found on the fork cap or inside the lugs, just like compression. Typically, clockwise is tighter or stiffer and counter-clockwise is looser or softer. To reset, turn in (clockwise) until it stops and then count clicks or turns out (counter-clockwise).

Bottoming out — The suspension has reached its lower limit, and can’t compress any more. You’ll hear and feel it when it happens... 

Topping out — The suspension has reached its upper limit. Topping out may make a “clang!” sound. Most new bikes have a top out spring (TOS) to manage this, so a clang on a TOS-equipped bike can signal an issue; it’s considered a wear item and can break. Frequent topping out or bottoming out indicates a suspension that isn’t optimized for its rider or terrain.

Feeling good with those terms? Let’s meet our expert.

Brandon Fleming is the suspension department manager at Solid Performance. Although Solid specializes in KTMs and Husqvarnas, Brandon’s helped countless riders as they begin tuning their dirt bike suspensions.

“I find that three out of four people at events don’t even have their sag set properly. They’re usually off by around 20 percent,” Brandon says. “It’s like suspension’s this mythical creature, nobody wants to touch it. But you can run those screws all the way in and all the way out, and it won’t break anything. So why not learn the basics and get your suspension in the neighborhood of where it should be?”

Simply setting the sag will make a huge difference in your ride. Brandon’s advice to rookie 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 motorcycle. Balance is the most important chassis setup item, as it affects handling as well as bump absorption.

Things you need to know about sag

There’s some debate over whether you should sit or stand while measuring rider sag, so I asked Brandon to weigh in on that. “When you ride, do you sit all the time, especially when cornering?” he asks. “Or do you stand? We should all be standing all the time, but not everybody does. Be honest with yourself, and accept how you ride. You can always re-adjust later.”

Yes, your body weight is the same whether you sit or stand. However, sitting or standing moves your weight distribution around on the bike, which is why there’s a difference. “Honestly, balance and sag matter when both seated and standing,” says Brandon. “ It’s important to be aware of rider feedback to feel if your balance is off and make adjustments on the fly, so be sure to carry tools with you on the trail or road!”

Many riders set sag when they first get a motorcycle and never adjust it again. Sag actually changes constantly based on temperature, life of the spring, and how many cheeseburgers and beers you’ve had in the last week! We all know that metal expands and contracts based on temperature, but riders don’t realize that a temperature change has any effect on sag and preload. Brandon finds that even 10 degrees difference can cause your sag to change. In addition, springs can eventually “take a set,” which means the overall length of the spring will change over time. You’d better believe that change affects sag.

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

Setting the sag on a dirt bike

Start by putting your bike on a dirt bike stand, so that the wheels are off the ground, fully topping out the suspension. Measure the distance from the axle block to a point directly above it on the bike’s fender. Use the same point every time you measure. (Some riders cut a notch or draw a line to mark their point. Newer KTMs have a spot with “SAG” molded into the plastic.)

Dirt bike on stand
Now that the bike is on a stand, the suspension is at full droop for free sag measurement. Be sure to use the same reference point each time you measure. The DR-Z250 has a gouge in the fender that I can easily find every time. Photo by Andy Greaser.

Got your number? Write it down and take the bike off the stand. Give it a couple bounces to ensure that it’s sitting naturally, and then measure again. (No rider on the bike yet.) The difference between your on-stand measurement and your on-ground measurement is the free sag, also called static sag.

Then the rider hops on. Get into the riding position! Hands on bars, feet on pegs. Stand up and sit down a few times to find your spot. Have a friend balance the bike (don’t rest on the side stand) and take that same measurement from the axle block to the fender, then subtract the resulting measurement from the on-stand measurement, aka full height. That’s rider sag, also called race sag.

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

Dirt bike shock adjustment collars
The shock collars may not be immediately accessible, but don't give up. I had to remove the air boot to expose the rings. Crud in the shock threads can be wiped away or blasted out with compressed air for smoother turning. Photo by Andy Greaser.

Maybe you find that your sag is already at the recommendation in your manual, or it’s right at the one-third mark. Sweet! You’re done, skip ahead to the fork section. For everyone else, it’s time to adjust the sag back into spec. Identify the preload adjustment on your rear shock, which is almost always a collar above the spring. Tightening the adjustment will compress the spring and increase preload, raising the bike’s resting position. Loosening will lower it. This is the time to use your spanner or shock punch to spin the preload adjuster.

Adjusting dirt bike shock collar
The Motion Pro shock punch has a brass end, so it won't chew up your collars like a steel screwdriver will. It took just a few taps from the hammer to get my collars spinning. Photo by Andy Greaser.

“Most preload collars have a lock ring of some sort,” Brandon says. “Yamaha has two metal ones. KTM has a nylon collar with a lock ring. They can be stubborn, and eventually somebody’s gonna be beating on that thing with a hammer and a screwdriver. Here’s a trick: Turn the spring by hand while turning the collar.”

Can’t spin the ring anymore? Either your threads are dirty, or the shock is so full of preload that you need to switch to a stiffer spring rate. Keep adjusting until you reach that one-third target. “It doesn't have to be scary," Brandon says. "It’s two fancy nuts. Spin them!”

Snug up the collars in their final position, and you've just adjusted your sag. Nice!

Once you have rider sag set, check the free sag measurement again. The correlation between free sag and rider sag is how you identify that you are in need of a spring change. If too much preload is added to the spring, the system will be close to being “topped out” and thus not allow the chassis to sag enough under its own weight.  Ideally, free sag should be 35 mm (+/-5 mm) on full height modern off-road bikes, and a smidge less for models with less than 300 mm of stroke.

Brandon swears by 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 this the easy button for adjusting pre-load and setting sag because there’s just an eight millimeter post to turn; no lock ring, no hammer and screwdriver, and most importantly, no busted knuckles!

Rider feedback

When the bike has too much sag, often called “choppered out,” the front tire is light or underloaded and the rear tire is overloaded. This will make the bike sluggish to turn, so the rider usually gets fatigue in the upper arms and shoulders from fighting the front end. The front tire will also deflect much easier, and may want to push or wash out when cornering. 

When the bike doesn’t have enough sag (“stink bugged”) 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 tuck or fall in when cornering and also feel like you are doing a pushup to keep yourself off the front end. The rider may also experience fishtailing in hard, straight-line acceleration. 

You can certainly check the front sag, though, which is usually 150 percent of the rear sag. (So if rear sag was 80 mm, front would be 120 mm.)

“Even WP/KTM/Pro Components doesn’t list these numbers,” adds Brandon. “It’s more rider preference.” Front sag is measured just like rear sag, so you’ll need to find a reference point. Brandon usually 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. Besides, most forks don’t have external preload adjustment, so it’s best to leave fork preload to intermediate and advanced tuners.  

Call up a suspension shop if your front sag is way off, because you’ll probably need a new set of springs. You can cheat your front sag somewhat by stiffening or loosening your compression (if equipped, more on that later), but if you’re bottoming or topping out after experimenting with compression, you’re probably going to need different fork springs. Most folks change fork and shock springs at the same time to ensure proper balance of the motorcycle

Adjusting fork height

For beginners, Brandon suggests leaving the fork alone. It’s easy to get spun out with all the adjustments.

Adjust dirt bike for height
See the two rings around the top of the fork leg? Use them to gauge fork height in the triples. Match the sides as carefully as you can, and take notes as you go. Photo by Andy Greaser.

Fork height is one variable you can change on any dirt bike. Most riders don’t think about how much difference the fork height makes, but sliding the fork legs up or down in the triple trees can seriously impact your ride. “Here’s a great example,” says Brandon. “We had an AA rider with pro components, chasing settings, but he just couldn’t find the feeling he wanted. Eventually, it was fork height adjustment that did the trick. He tried everything else and just overlooked it.”

Moving the fork down in the triple tree increases the bike’s wheelbase, adding stability in straightaways at the expense of some maneuverability. Sliding the fork legs up through the triple tree will make the bike turn tighter and faster, although it may feel more squirrely at speed.

With sag set and the fork squared away, it’s time to address compression and rebound, if your bike has those adjustments.

Adjusting compression and rebound: The clicker exercise

Brandon and the rest of the Solid crew recommend this clicker exercise to help riders get a sense of their suspension settings. Start by setting your rebound and compression clickers to the factory standard setting on both the forks and the shock. Write that setting down, and take the bike for a five-minute loop of your average terrain. When you get back, write down how the bike felt. Did you like it? Was it stiff? Plush? Then go two clicks in/stiffer on compression and one click in/stiffer on rebound on both the forks and the shock.

Rear shock clickers dirt bike
The budget-blaster DR-Z doesn't have an array of clickers, but RevZilla's CRF450R does. You'll be spending time with these adjustments in the clicker exercise. Photo by Andy Greaser.

Dirt bike fork adjustments
You'll find the corresponding fork adjustments here, on the caps. Our CRF happens to have an air fork. There's a section on tuning those below. Photo by Andy Greaser.

Adjusting the forks and shock together help keep the bike balanced. This two-compression-for-one-rebound rule scales the two adjustments pretty well on most bikes, and in the same direction. Take the bike out for another five minutes on the same loop and note your impressions. Better? Worse? Turn in another two clicks of compression and one rebound, and repeat until additional changes just feel worse, then return to factory standard setting. Now, use the two-one rule to add compression and rebound in the opposite direction (out/softer). When you become more advanced with your adjustments, switch back to only adjusting one thing at a time. The 2:1 rule helps riders mainly become familiar with the range of “feel” the suspension has to offer. Many professional riders who are able to discern minute changes will make one adjustment at a time to isolate the positive changes.

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

Your dirt bike should be more comfortable and confidence-inspiring after the tuneup. That wasn’t so bad, was it? Your next steps into the world of suspension tuning will likely involve some interactions with a tuning shop like Solid Performance, but for now, you understand the basic functions of suspension adjustment, and your bike is better optimized for your weight and riding style. That’s a big win.

You might find that your “happy place” setting is way out at the edge of your adjustment range, and that means you’ll want to talk to a tuner for new parts or revalving. Think of suspension like a suit. You can wear one off the rack 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 what you feel in the suspension, or to know what to feel for. Brandon has a few pointers for these riders. 

“We want you to use all your suspension,” Brandon says. “Bottoming happens. Bottoming all day, every day is a problem. That’s why tuners install travel indicators on a fork, like an O-ring or WP travel indicator. Don’t use zip ties for this! They score your chrome. If you’re bottoming out constantly, no matter your setting, you should talk to a shop. You want it to be compliant, but not blowing through the stroke. Learning when to make what adjustment is not easy, which is why we default back to that clicker exercise.”

It can be tough to judge sag feel at first. When you have too much sag, the rear is too low compared to the front, and you might have headshake when cornering on the road from that light front wheel. With the opposite, too little sag in the rear, the front tire wants to grab too much. Instead of sliding or washing, the bike wants to fall over when cornering, and it feels like a pushup to turn. There might be some side-to-side fishtailing when going hard in a straight line. 

My bike has high-speed and low-speed adjustments. What’s up with that?

Brandon gets this question frequently. “People think it has to do with bike speed,” he says. “Nope. It’s the speed of the suspension movement. Bucking, hopping, kicking is high-speed. Bottoming, hard hits, too. Low-speed covers the rest. Just remember it’s about 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. High-speed compression is usually a 17 mm nut. High-speed compression changes are often measured in turns. Just a quarter turn would be noticeable.

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 inside. It’s important that the front end is suspended (like on a stand) when checking pressure, as pressure will change based on where in the stroke the fork is setting. For example, a WP AER fork’s standard pressure is around 10 Bar (~145 psi) and when that fork bottoms out, the pressure can hit 70 Bar (~1015 psi). 

Changing at an increment of 0.2 Bar (~3 psi) is a good place to start. Many riders mistakenly think air pressure controls stiffness, and only focus on air pressure without changing compression or rebound on the fork. As stated above, it’s important to change one thing at a time. 

Try changing air pressure in small increments without touching anything else. Then adjust compression and rebound. If time allows, try the clicker exercise at a few different air pressures to find the best pairing. Whether you’re using air or spring forks, spring rate and clicker settings drive the feel of the bike together.

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

In Brandon’s opinion, no! But wrong ones definitely exist. “We had a guy who loved his setup, but then he changed it to ride another terrain by softening compression five clicks and stiffening rebound by two clicks. He thought the bike ‘felt stiff’ in the different terrain, so he went out and softer on compression, and tried turning the rebound in and stiffer to keep it from pogoing. But it sucked! The problem he created is called packing, since the softer compression had him riding lower in the stroke, and with it now stiffer coming out of the stroke, it was just staying down, and the bike could never come back to full height. If he went back to his base setting and followed the two-one rule, he’d have found something better, and then he could make the fine adjustments from there.”

“As a general rule, the faster you go, the stiffer your settings need to be. When you slow down with suspension set up for a fast pace, it won’t feel great, especially when you’re fatigued, so this is where the clicker exercise starts to work. Be realistic with your riding. If it’s an off day for me, I’m backing clickers out on my bike and just getting the most out of the ride and how I feel.”

What are the biggest mistakes riders make when adjusting their own suspension?

“The biggest mistake I see is that ‘set it and forget it’ mentality,” Brandon explains. “Really, there’s two types of mistaken riders I meet. You have the N’th degree types, adjusting everything all the time, and the problems are never the rider’s fault… and then there’s the other type that sets the sag once and never touches it again. Get familiar with making changes to your suspension, especially if you have air forks. Be aware of what the adjustments do, so that you don’t get frustrated or scared to change as well as recognize how you’re performing that day.”

“Another problem I see is buying the wrong motorcycle for the wrong application. People spend all this time adapting an inappropriate bike’s suspension to handle what they actually want to do. Look, you can throw tons of money at it, or just admit that you bought the wrong bike and trade it out.”

“Ignoring service intervals is one more 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 at 40- to 50-hour intervals, and we’re usually the ones fixing the big issues when people skip maintenance. We see loads of worn parts, and sometimes entire components are smoked. Regular suspension maintenance leads to not just better ride quality, but also lower cost of ownership when factoring the potential expense of costly broken internal parts from neglect. Linkage parts and swing arm bearings are also badly neglected. So keep up on your regular chassis bearing TLC, especially if you love your pressure washer.”

Hopefully your bike feels better, you’re accustomed to turning clickers, and your sag is right on the money. Nice work! The suspension on our dirt bikes is meant to make riding even better, after all, but it can’t do that without a little know-how and attention. Have fun!