Setting the sag on a dirt bike will improve the dirt bike’s performance and improve your riding. Whether you ride motocross, enduro, or on trails, setting the dirt bike sag should be the first thing you do to your newly acquired dirt bike.
To clarify, the sag affects the balance and performance of the dirt bike. Your total riding weight with riding gear on defines how much preload and tension is required on the rear shock spring. If you have noticed bottoming out or harsh rear shock feedback or just overall unstable riding feel, you should set your dirt bike sag to recommended settings.
Setting the sag on a dirt bike starts with measuring the current free sag and the total sag. The free sag equals the distance difference measured from the rear fender to the swing arm, with the dirt bike on a center stand and when standing free. The total sag equals the distance with the dirt bike on a center stand and with a rider weight on the dirt bike. To set the dirt bike sag correctly, add or remove preload on the rear shock spring.
Next, let’s dive into how dirt bike sag affects riding performance and how to adjust your dirt bike sag.
What Does Setting the Sag Mean on Dirt Bikes?
Do you know how to set the dirt bike sag by yourself? The sag adjustment on a dirt bike can be performed with a tape measure and it takes about 30 minutes to complete.
Setting the sag on a dirt bike refers to the rear shock spring tension and preload settings. The sag needs to be adjusted to your overall weight with full riding gear on. Additionally, a correctly set sag on a dirt bike will balance the suspension performance and will help to fine-tune the rider feedback to fit your riding style, preferences, and performance requirements.
How Does the Sag Affect Dirt Bike Riding?
A badly set sag can cause the following symptoms:
- Rear shock bottoming out
- Harsh feeling when hitting obstacles
- Bouncy or inadequate rear shock dampening
- Unstable performance in higher speeds
- Unbalanced suspension performance with the front suspension
- Rear of the dirt bike sitting lower or higher than front
Setting the dirt bike sag simply means adjusting the rear shock to your weight and riding style. You will achieve the recommended sag by adjusting the rear shock spring preload. You can do this by rotating the spring preload adjustment plate.
What Is a Free Sag or Static Sag?
A free sag (sometimes called a static sag) on a dirt bike refers to the distance difference between the rear fender and the swing arm when measured without any suspension load and with the weight of the dirt bike. Simply put, measured with the dirt bike on the center stand versus when the dirt bike is standing on its own. Typically, the dirt bike drops about 30mm or 1.25″.
What Is a Total Sag or Rider Sag?
A total sag (sometimes called a rider sag) on a dirt bike refers to the distance difference between the rear fender and the swing arm when measured without any suspension load and with the total weight of the dirt bike and the rider. In simple terms, measured with the dirt bike on the center stand versus with the dirt bike and the rider standing on the foot pegs. Typically, the total sag on a full size dirt bike is about 110mm or 4.25″.
How To Set the Sag on a Dirt Bike With a Tape Measure
Setting the sag on a dirt bike begins with checking the current spring rate. Next, you need to measure both the free sag and the total sag. These measurements will tell you if you need to tighten or loosen the rear spring preload to achieve an optimal sag. Refer to your service manual for exact recommended sag settings.
Recommended Tools for Setting the Sag on a Dirt Bike
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Typically, you can rotate the spring with the preload plate by hand and no other tools are needed. However, a good shock spanner wrench (check the current price on Amazon.com) can help if the spring is difficult to move or if it’s stuck. This tool is sometimes referred as the dirt bike sag tool.
The tool generally makes the sag adjustment on dirt bikes easier, especially on older dirt bikes. Clean the threads properly before adjusting the rear springs as the lock ring is typically plastic and dirt on the threads can cause issues.
Step 1: Check the Current Spring Rate
Start by checking your current rear shock spring for the load rating. For example, if you have the factory spring, they are usually designed for a rider weighing about 160 pounds or 75kg with gear on.
The spring rate is written on the spring and you need to google the spring rate to cipher the weight range it is set to. Set the dirt bike on a center stand and rotate the spring to find the spring rate.
If your weight with gear on doesn’t match the spring, you need to change to a correct spring. Note that if you try to set the sag and you struggle getting both the free and total sag to your desired settings, this usually means that the spring rate is not matching to your weight.
Once you have found and confirmed the spring rate, continue to set the dirt bike sag by measuring the free or static sag.
Step 2: Measure the Current Free or Static Sag
Once the dirt bike is positioned on the center stand, measure the distance between the rear fender and the swing arm. We mark the measuring point with a pencil on the fender to ensure accurate measurements later on.
Next, measure the distance from your mark on the fender to the swing arm. Write down the distance.
Next, move the bike off the center stand and let it stand freely upright while pushing down on the seat few times. When setting the sag on a dirt bike, the goal is to see where the bike naturally wants to level without any weight on the dirt bike.
Now measure again and write down the distance. Calculate the difference between the two distances. This is called a static or free sag. You should be looking at a measure of 30mm or 1.25″ on full size dirt bikes.
Step 3: Measure the Current Total Sag or Rider Sag
Now hop on the dirt bike with your full riding gear on. We use the center stand as an aid to hold the dirt bike up straight while bouncing on the pegs few times. Make sure you have all riding gear on and that you are centered on the dirt bike. Do not sit or lean back or forward too much.
After finding the level position with you standing on the pegs, have a friend measure the distance once again. Write down the distance.
Next, calculate the difference between the distance when the dirt bike was on the stand (that is the very first measurement you wrote down or max distance) and the distance with the rider on the dirt bike (that is the very last measurement you wrote down or sag measurement). This is your total sag or rider sag.
Dirt Bike Sag Calculator
| Sag Type | Max Distance | Sag Measurement | Sag |
|---|---|---|---|
| Free Sag or Static Sag | 25 1/4″ | 23 7/16″ | 1 5/16″or 1.31″ or 33mm |
| Total Sag or Rider Sag | 25 1/4″ | 21″ | 4 1/4″ or 4.25″ or 107.95mm |
Setting the sag on a dirt bike refers to the free and total sag measurements and adjusting the spring preload.
First and foremost, refer to your dirt bike manual for the recommended free/static sag and total sag. Usually, the static sag should be around 30mm (or 1.25in) and the total sag around 105mm (or 4.25in).
And voilà, now you know how to measure your dirt bike sag. If your static sag and total sag is within the recommended range, you are good to go!
Next, we will cover how to set the sag on a dirt bike and adjust it to the correct range.
Step 4: Set the Dirt Bike Sag – Loosen the Rear Spring Lock Ring
Set the dirt bike on a center stand and make sure that the rear tire is completely off the ground. Loosen the lock ring around the spring on the top side. Once loose, rotate the spring with the treaded top ring to adjust the preload on the spring.
Step 5: Set the Dirt Bike Sag – Rotate the Rear Spring To Adjust Sag
If your total sag is too high, you need to add preload, essentially making the spring stiffer. This is achieved by rotating the spring tighter, usually clockwise looking from the top of the dirt bike. When rotating the spring, make sure you are also rotating the spring preload plate. Hold both the spring and the preload plate with your hand and rotate them together.
And if you need to do the opposite, loosen the spring preload to increase the sag. After adjusting the spring, measure again and adjust more if necessary. When you adjust the spring, you will notice that both the static and total sag is affected. This is normal.
If you cannot find a setting where both sag distances are within the range, it’s usually because the spring is incorrect for your riding weight. Another reason can be sticking shock bushings or swing arm bearings.
Step 6: Set the Dirt Bike Sag – Tighten the Rear Spring Lock Ring
Don’t forget to measure both the free and total sag after each time adjusting the preload. The preload will affect both measurements simultaneously. Once you have reached the recommended sag measurements, you are ready to finish up.
Finally, don’t forget to tighten the spring lock ring and write down the latest sag values for the next time. Old measurements are helpful when troubleshooting or fine-tuning the sag for different riding styles.
Recommended Dirt Bike Sag for Trail Riding
Start with the recommended sag settings. This is typically a good setting for most trail riding.
To fine-tune the sag settings for trail riding, we recommend setting a slightly shorted total sag for very technical trail riding. This means adding the preload to achieve a total sag around 105mm or about 4″. The stiffer rear spring will help to keep the rear slightly elevated, which benefits when hitting obstacles at higher speed. Match the rebound speed clicker settings to fine-tune based on the feedback.
For faster, more flowy single track or trail riding, keep the recommended sag settings or slightly softer around 115mm or 4.5 inches of total sag. Add few compression clicks to avoid bottoming out and adjust from there.
Conclusions
Setting the dirt bike sag is a quick and easy method to increase the suspension performance. It will also help your riding as the dirt bike is more stable and predictable. This will help you use less energy and ride faster and longer.
Setting the sag on a dirt bike also balances the dirt bike. This helps especially at higher speeds and in rocky, bumpy, and technical terrain. If you are a motocross rider, the sag will effectively prevent bottoming out and keep the dirt bike from diving in and sagging the rear.
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