Dirt Bike Suspension Adjustments Made Easy

There’s nothing like the feeling of riding with telepathy, when everything works in harmony and man and machine become one. Proper suspension settings are the key to that balance. A few hours of work can transform your dirt bike from a bucking bronco into a tight triathlete, poised for action, ready to roll.

Power and torque don’t mean jack if they can’t make it to the ground. If your dirt bike isn’t reacting to the terrain and communicating it effectively, you can’t ride at your peak potential. But suspension adjustments at a shop are inconvenient and expensive. There’s no reason you can’t do it yourself for free!

This handy guide explains dirt bike suspension adjustments from a hobbyist perspective. And as you're about to see, there's lot to gain from a little work.

Performance Gains

If you feel like your bike sometimes gets out of hand, if you wish it were more controlled at certain places on your favorite trail, or even more wild and unrestrained, you have the power to make that happen. Follow this guide the first time and soon you’ll know what adjustments to make without even thinking.

Before we begin, you should be confident with a wrench and okay with working on critical areas of your bike. Mistakes here can cause the bike to lose control more readily, potentially resulting in an accident. Our lawyers told us to say that. Carry on.

Tools

In general, you shouldn’t need any special tools. A shock wrench would help but a hammer and punch will usually do the trick. Have a crescent wrench, box wrenches, sockets, and screwdrivers handy. Lastly, a good penetrant like PB Blaster will help motivate sticky parts.

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Types of Suspension Adjustment

You might be tempted to play the middle with your dirt bike’s suspension settings, but that won’t result in the best handling. It’s best to make suspension adjustments for each terrain style you encounter, even making minor adjustments throughout the day to get the most from certain sections of the course. But for now, there are 3 key factors to motorcycle suspension:

Sag

This is the most critical aspect of getting your dirt bike to feel right. Free sag is how far the bike hunches down under its own weight, and rider sag is how far the suspension compresses with a rider onboard. Changing the sag alters your ride height and the softness of the suspension. Less sag makes for a more steerable bike that’s less stable at speed, while more sag predictably does the exact opposite. Sag is changed by adjusting spring preload.

Preload

This refers to how compressed the spring is when it’s at rest. In other words, preload is how much tension is always on the spring. More preload results in harsher suspension because the spring constantly wants to expand. Naturally, less preload makes for a softer ride. Too far either way and your dirt bike’s handling will fall somewhere between a cheap go-kart and your great-grandpa’s Lincoln.

 Sag illustrated.  source

Sag illustrated. source

Damping

Something has to keep the springs in check – damping controls how quickly the shock and forks respond to the riding surface. A slow shock is optimal for rolling hills, while a fast shock is better for rough terrain. That’s commonly referred to as low-speed and high-speed damping, respectively.

Damping is the product of compression and rebound. Compression controls how quickly the spring compresses; rebound controls how fast it expands again. You should see the letters C and R accompanied by arrows somewhere on your shock and forks – if you don’t, chances are these settings can’t be adjusted on your hardware.

Summary
Dirt bike suspension consists of sag, preload, and damping. Successfully adjusting these key areas will increase performance across the board. This job takes minimal effort and best of all, it doesn’t cost a thing.

Rear Suspension Adjustments

Rear spring preload

We’ll start at the rear, where there’s generally more control over a dirt bike’s stock suspension.

First, measure rider sag. Put your bike on a center stand and, using a tape measure, measure a straight line from somewhere on your rear fender or mud guard to the center of the axle nut. Then don all your riding gear (even a helmet), take the bike off the stand, and stand on the pegs. Bounce a few times to work out any stiction, then have a helper measure that same distance again. Subtract small from big and viola, you have your rider sag figure. Look for a number between 95mm and 115mm, or about 33% of the rear end’s total possible travel.

Change sag by loosening the lock ring and adjusting the spring preload ring using a hammer and punch.

  • Turning clockwise increases preload, and vice versa
  • More preload results in less sag, and vice versa
  • Each full turn changes sag by about 3mm

Repeat the process of measuring, sitting, and measuring until you reach the desired sag. The owner’s manual, a shop, a friend, or the forums can help you determine the optimal sag settings for your needs.

Next, measure free sag by measuring that same line when the bike is sitting by itself, off the stand. Look for a number between 25mm and 45mm to confirm that you have the correct spring rate. A figure near or below 25mm means you need a harder spring; near or above 45mm says you need a softer one, for optimal performance.

Needing a different spring is common if your body weight falls at either end of what may be considered average. You will also need a new spring if the shock’s preload must be dialed to either extreme to reach the correct sag, or if it’s dialed out and the sag still isn’t right. And given enough time, springs just wear out. Companies like Racetech make aftermarket front and rear springs of various rates.

It’s worth mentioning they make tools for measuring sag, like the one pictured above. Having one isn’t necessary but it will make life easier down the road.

 Sources  1 ,  2

Sources 1, 2

Rear damping

Adjustment points are going to vary based on your bike. Öhlins makes it easy as you can see, and if your bike doesn’t have points like those your hardware may not be adjustable.

As far as numbers go, check the web for recommended settings for your bike. Those figures will make a good baseline to work from. The goal is to retain enough compression to avoid bottoming out and enough rebound to maintain traction while avoiding a bouncy ride.

Low speed compression: Adjusted with a nut at the top of the reservoir, often clicks when turned.

High speed compression: Either incorporated into the low speed nut or a separate nut near that area.

Rebound: Adjusted at the bottom of the shock, often using a wheel or a flathead screwdriver.

Front Suspension Adjustments

Front spring preload

Preload adjusters are often found at the top of the fork and are changed using a knob, wrench, or screwdriver. Most modern forks allow for preload adjustment, but many older models don’t – find your model-specific details online. If your forks don’t have an external way of changing preload, it’s probably impossible without internal modifications.

In general terms, your dirt bike’s sag and free sag should be about the same front and rear. They don’t have to be identical, but a big difference will upset the bike’s balance and lead to poor handling. As with the rear, if your front sag and free sag values are way off or your forks are dialed to an extreme, you may want to buy new fork springs to better suit your weight.

Front damping

Many modern dirt bikes have forks that differ wildly from those of previous generations. In the old days, both forks would house springs and damping components. External adjustments were often limited and both sides had to remain even. Many of today’s machines use Separate Function Forks, where one fork holds a spring and the other controls damping. High-end forks take this even further by using pressurized air instead of springs and by controlling damping with oil (viscous damping).

Once you know what hardware your dirt bike has, adjustments are easy.

Rebound damping: Generally adjusted at the top of the fork using a flathead screwdriver or twist mechanism.

Compression damping: Often found at the same place, sometimes found near the bottom of the fork.

Tips and Tricks

Unless you’re living the stance life, your bike shouldn’t look like that on a regular basis.

Getting the right balance of compression, rebound, and preload is tricky. But like anything else, it’ll become second nature before you know it.

Most dirt bikes arrive from the factory with middle-of-the-road settings. It’s best to verify that you’re at the middle and go from there, taking note of what effect each change has on your bike’s handling. Learn those effects before you go balls-out on fresh suspension settings – you wouldn’t want the bike getting out of hand when you least expect it.

Dirt Legalize Your Dirt Bike

Why keep all that fun off the road? Tuning suspension for a street legal dirt bike is the same process, but the goal is very different. But long before you wrench on your bike it needs a title and tag to be street legal. That's where we come in. Call or click to learn more, or have us call you:

Did we miss anything? Let us know in the comments!

Cover image source