What Is Motorcycle Preload? A Comprehensive Guide to Its Necessity, Adjustment Procedures, and Methods!

What is motorcycle preload adjustment?

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"Preload" is a term that comes up in relation to motorcycle suspension. The English word "preload" means to apply a load beforehand, or to load something in advance.

Preload adjustment refers to applying a load to the suspension spring in advance to adjust the suspension's stroke amount (the amount it moves up and down).

What's the difference between preload and suspension?

Preload means to apply a load to the suspension in advance, while suspension is a part that softens the impact of uneven road surfaces and supports the rider's weight.

When carrying heavy luggage or riding with a passenger, adjusting the preload allows the preload to support the weight, thus maintaining the proper suspension stroke.

Some models, especially large motorcycles, are equipped with shock absorbers that have a preload adjustment (also called initial adjustment) mechanism. Utilizing this effectively can lead to a ride feel that suits your preferences.

What happens if you increase the preload?

Increasing the preload means increasing the load already applied to the suspension, putting the suspension in a compressed state.

Compared to an uncompressed state, the suspension won't compress without a larger vibration, making it less responsive to small vibrations and resulting in a stiffer ride.

If the preload is set too high, the suspension stroke is significantly restricted, meaning your body will directly absorb vibrations from uneven road surfaces while riding.

Many motorcycles only have rear preload adjustment.

Many models with preload adjustment features often only have them on the rear shock. To check if your motorcycle has this feature, refer to the owner's manual.

Sport bikes, like those used on circuits, may have preload adjustment on both the front and rear, allowing for more flexible adjustments depending on the riding situation.

For models with front preload adjustment, the adjustment is located on the top cap of the front forks and is adjusted by turning a hexagonal nut-like structure.

What happens if you decrease the preload?

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If you decrease the preload, the initial load applied to the suspension becomes weaker, causing the suspension to extend and improving ride comfort.

The suspension will compress more easily, which also improves foot reach when straddling the bike. It is especially recommended for lighter riders to set a lower preload.

Additionally, the bike will react better to uneven road surfaces, absorbing even small vibrations.

About the terms for increasing and decreasing preload

When adjusting preload, various terms are used, such as "increase/decrease" and "apply/not apply."

We will explain the meaning of each term related to suspension and preload, so please use this as a reference for adjustment.

<h4>Increase/Decrease</h4>

To "increase" the preload means to strengthen the initial load on the suspension, resulting in a firmer ride. This is recommended for heavier riders or when carrying heavy luggage on long tours.

Conversely, to "decrease" the preload reduces the load on the suspension, which improves foot reach and ride comfort, making it suitable for lighter riders.

If you increase it too much, road-holding ability will worsen and ride comfort will deteriorate. If you decrease it too much, road-holding ability will improve, but the shock might bottom out from strong impacts from the road, so avoid extreme settings.

Apply / Not apply

To "apply" preload means to put an initial load on the suspension, and some models offer 10 or more levels of strength for this application.

When you "don't apply" preload, it means no initial load is put on the suspension, allowing for the pure movement of the suspension itself.

High/Low Ride Height

"High ride height" means the suspension is extended, raising the overall height of the motorcycle. This also raises the center of gravity, making it more susceptible to being pushed around, especially by crosswinds on windy days.

Increasing ride height also improves off-road capability, which is why off-road motorcycles designed for rough terrain have higher ride heights compared to naked bikes or faired sport bikes.

"Low ride height" refers to a state where the suspension is compressed or when short-stroke suspension is installed, resulting in a lower overall height. If you only lower the ride height on a suspension without preload adjustment, the stroke amount decreases, worsening the ride quality.

Heavy/Light Rider Weight

For a "heavy" rider, it's generally best to increase the preload. The same applies when carrying a passenger or heavy luggage.

Conversely, for a "light" rider, it's generally best to decrease the preload. This allows the suspension to compress more easily even with a light load, improving foot reach.

If the preload is too low, the downward force on the tires (traction) also weakens, leading to poor road contact and increasing the likelihood of an unstable state during cornering or braking.

Therefore, proper preload adjustment is crucial to prevent unstable motorcycle behavior.

Turn Left / Turn Right

For rear shock preload adjustment, turning it "to the right" increases the preload, and turning it "to the left" decreases it.

If you want to stiffen the shock's movement by engaging the preload, or if you are a heavier rider, turn it to the right from the initial position. If you want a softer shock movement, or if you are a lighter rider, the basic adjustment is to turn it to the left.

When is motorcycle preload adjustment necessary?

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Motorcycle preload adjustment is mainly necessary in the following situations:

• When the rider's weight is too heavy or too light
• When riding with a passenger or carrying heavy luggage
• When impacts from the road surface are strong
• When the feeling of contact with the road is weak

We will explain each of these in order below.

Rider's weight is too heavy or too light

If the rider's weight significantly exceeds 65kg, or conversely, is too light (e.g., in the low 50s or 40s kg), adjust the preload to achieve optimal ride comfort.

If the rider is heavy, increasing the preload will allow the suspension to function effectively even under high load. Conversely, if the rider is light, decreasing the preload will improve suspension movement and foot reach.

When carrying a passenger or heavy luggage

Preload adjustment is also necessary when riding with a passenger or carrying heavy luggage on long tours.

When the motorcycle is under a significant load, increasing the preload will result in optimal suspension movement.

However, if it's too strong, road-holding ability will worsen and ride comfort will significantly deteriorate. Therefore, try different preload values while riding to find the optimal setting.

When impacts from the road surface are strong

When riding on rough roads, or when there are strong bumps (impacts) from the road surface, adjusting the preload can reduce strain on your body.

When impacts from the road surface are strong, or when constantly riding on uneven surfaces, decreasing the preload will improve shock absorption. However, if it's too low, the shock might bottom out, so adjustment is necessary to prevent bottoming out.

When the feeling of contact with the road is weak

If you're riding on winding roads with continuous curves and you feel a weak or floating sensation of tire contact with the road, try adjusting by reducing the preload.

Sport bikes and imported motorcycles are often set up for higher speeds, with stiffer suspension. On public roads, reducing the preload can increase road contact.

Also, if you have trouble reaching the ground, reducing the preload will increase suspension sag and improve foot reach. Lighter riders should definitely try this.

Motorcycle preload adjustment procedure

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Below, we will explain the steps for motorcycle preload adjustment in order. If you ride a motorcycle with preload adjustment, please refer to this.

To check if your motorcycle has preload adjustment, refer to the owner's manual, as it will describe the adjustment method if available.

Precautions for preload adjustment

When adjusting the preload on a dual shock, always ensure that both sides have the same adjustment value.

If the preload values on both sides are different, it can lead to unstable riding and is dangerous. Therefore, always set both sides to the same value. However, for a monoshock, there is only one adjustment point, so there is no need to worry about this.

Precaution 1: Turn the suspension adjuster.

Preload adjustment requires a tool called a hook wrench, which is usually included in the onboard tool kit of motorcycles with preload adjustment, though some models can be adjusted by hand.

Motorcycle rear shocks can be either monoshock (single shock) or dual shocks (one on each side). A monoshock is located near the center of the rear tire, so the adjustment adjuster might be difficult to turn.

You set the preload by turning the adjustment adjuster. It's easiest to get a feel for the stiffness and make adjustments if you first try both the strongest and weakest settings.

Precaution 2: Straddle the motorcycle and check the change.

Once you've set the preload by turning the adjuster, actually sit on the motorcycle and check the changes in the suspension.

Key points to check are how much the suspension sinks when you sit on it, how much it sinks when you lightly apply weight, and its shock absorption.

It's a good idea to ride on various roads, gently, to check how it feels on straightaways, in curves, and so on.

Precaution 3: Make fine adjustments as needed.

After checking the suspension's movement while sitting on the motorcycle, make fine adjustments as needed.

While fine adjustments might seem tedious, repeating them will help you find your preferred setting.

If you try adjusting the preload repeatedly and still can't find a comfortable setting, it might be a good idea to consider changing the suspension's stiffness (

spring rate) or even replacing the shock absorber itself, to address the root cause.

Precaution 4: Make a final confirmation by actually riding.

Once the fine adjustments to the preload are complete, actually ride the motorcycle to check the vibration from the road and the suspension's movement.

If the preload has been significantly changed, there will be a big difference in the suspension's movement and the ride quality. So, like when you first receive a new motorcycle, ride carefully and observe its behavior to confirm.

If you feel any discomfort, make further fine adjustments and then test ride again until you find your preferred setting.

Summary

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We've covered the basics of motorcycle preload, from what it is to its effects on the bike.

We've also explained how to adjust preload, so if you ride a motorcycle with preload adjustment, please make adjustments to suit your riding scene and environment to enjoy optimal motorcycle riding.

To determine if your motorcycle has preload adjustment, check the owner's manual; if it does, the adjustment method will be described there.