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Basics of Bicycle Tire Sealant

The Role of Sealant in Bicycle Tires

Sealants used in road bikes and MTBs are special liquid compounds that are inserted into the tire or tube for the following purposes:

1. To fill gaps and prevent air leakage
2. To temporarily seal punctures

Thanks to their unique properties, sealants can fill even sub-millimeter gaps between the rim and the tire, preventing slow leaks.

Moreover, sealants are also effective for temporarily sealing punctures. When a puncture occurs, the escaping air pushes the sealant toward the hole, where it coagulates and seals the leak.

Types of Bicycle Tires That Use Sealant

Bicycle tires are generally classified into the following four types:

1. Clincher (tubed)
2. Tubular
3. Tubeless
4. Tubeless Ready

Let’s look at how sealant is used with each type:

Sealants are mainly used for temporary puncture repair in all tire types except for clinchers. However, when it comes to preventing air leakage, only tubeless-ready tires require sealant.

Most of the tubeless-compatible tires and wheels currently available on the market are of the tubeless-ready type, which means they require sealant to maintain air pressure. Without sealant, air leaks through the microscopic gaps between the tire and the rim.

While it’s possible to use sealant in clincher tires (by injecting it into the tube), it’s generally not recommended due to the added weight. In most cases, replacing the tube is a simpler and lighter solution.

Types and Characteristics of Tire Sealants

There are several types of sealants for tubeless tires, but they can generally be categorized into the following two types:

1. Latex-based sealants
2. Synthetic rubber-based sealants

In addition, some products include solid particles to help seal larger punctures more effectively.

Here are the characteristics—both advantages and disadvantages—of each type:

Product prices vary as well, so it’s best to consider your budget along with the pros and cons of each type when choosing a sealant.

Benefits of Using Sealant

You Can Still Ride Home After a Minor Puncture

Sealant serves to fill small gaps, so if a tire is punctured, it can seal small holes. While it doesn’t completely repair a puncture, a well-sealed tire can resist losing air even when punctured multiple times by nails.

For example, Black Ox, a sealant manufacturer, has even posted a video showing a sealant-filled MTB tire being shot with a rifle without going flat.

Tubular tires, which are popular in road racing, integrate the tube and tire into a single unit. This means a puncture usually requires a complete tire replacement. If you puncture multiple times during a ride, you might run out of spare tires. By contrast, using sealant in tubeless tires allows the sealant to fill holes and keep you riding for a while.

Although it may not be suitable for continuing a long ride, you can likely make it home or to the nearest station. Some riders even carry sealant and a pump to re-inflate the tire and continue their ride after a puncture.

Useful to Keep One Bottle Around for Future Tubeless Setups

There is little difference between sealant used for tubular and tubeless tires—mainly viscosity.

This means that if you’re currently using tubular tires, the same sealant can likely be reused later when switching to a tubeless-ready setup. Since sealant only costs about ¥300–600 per tire, any leftover can still be used.

If you ride multiple bikes—for example, a tubular road bike for racing and a tubeless-ready gravel bike for leisure—you can standardize your puncture protection and reduce what you carry by using the same sealant for both.

Disadvantages of Using Sealant

Messy Until You Get Used to It

For experienced riders or professionals, using sealant isn’t an issue. However, beginners may struggle with application and end up making a mess—sometimes coating their entire room in sealant. This is especially likely if you try injecting sealant without fully deflating the tire first. That said, carefully following the manufacturer’s instructions can prevent most problems.

With tubeless-ready tires, if you get a flat while out riding, you’ll likely need to install a new tire and add more sealant on the spot. Handling an old, sealant-filled tire will definitely get your hands dirty, so it’s a good idea to carry rubber gloves in your repair kit.

Added Weight

You typically need about 30–60 ml of sealant per tire, which can add up to roughly 100 g for two tires. While that may not sound like much, every gram counts for cyclists aiming to reduce the weight of their road bike.

For sealant to work properly, it must be applied in sufficient quantities. Diluting it or using too little will reduce its effectiveness.

Requires Regular Top-Ups

Sealant doesn’t last forever. Depending on the brand, it usually evaporates after 6 to 12 months. This means you’ll need to reapply it regularly to maintain effectiveness.

While tubular tires can still function without sealant, tubeless-ready tires rely on it to stay inflated. Without sealant, air will slowly leak out, so periodic maintenance is essential.

This is a disadvantage not shared by clincher tires, which can often last a year or more without attention—as long as you don’t get a puncture.

Recommended Amount of Sealant and Refill Interval

How Much Sealant to Use

The recommended amount of sealant varies depending on the brand. For example, Stan’s—the company credited with pioneering the tubeless-ready system—recommends the following:

1. 1–2.4 inch tires (23C–60C): 60–90 ml
2. 2.5–4 inch tires (63C–100C): 90–120 ml

These figures are general guidelines from the sealant manufacturer. In practice, narrow road bike tires can often hold air for a long time even with less than the recommended amount, while wider MTB tires may lose all air overnight if the quantity is too low.

Because of this, it’s a good idea to start with the lower end of the recommended amount—or even a bit less—and then leave the tire overnight. If air leakage occurs, add more sealant accordingly.

How Often Should You Add or Refill Sealant?

Sealant naturally dries out over time and does not remain effective indefinitely. Therefore, regular top-ups are necessary.

As a general rule of thumb, you should replenish sealant every six months. In some cases, particularly in hot or dry environments, you may need to add more every two months.

However, the actual lifespan of sealant inside your tire depends on several factors:

• How often you ride
• How and where the bike is stored (humidity, temperature, etc.)
• The compatibility between the sealant and tire

Some setups may last over six months, while others may dry up in just one month.

A simple way to check is by removing the wheel and shaking the tire. If you no longer hear the sloshing sound of liquid sealant and you’ve noticed increased air loss recently, it’s likely time to add more.

How to Choose Sealant for Road Bikes and MTBs

Choose Products from Reputable Brands

When selecting a sealant for road bikes or MTBs, it’s best to go with well-known products from dedicated bicycle component manufacturers.

Popular sealant brands include:

1. Muc-Off
2. Panaracer
3. Stan’s NoTubes
4. Vittoria
5. BLACK OX
6. Mavic
7. IRC (Inoue Rubber Company)

The best sealant for your setup may depend on compatibility, so there’s no one-size-fits-all answer. However, sealants from reputable brands tend to offer more reliability than those from lesser-known manufacturers.

Check for Manufacturer-Specific Requirements

In some cases—particularly with tubeless-ready tires and wheels—the wheel manufacturer may specify compatible tire and sealant brands.

While it’s not impossible to use non-specified products, the performance metrics claimed by the manufacturer are typically based on their recommended combinations. To ensure optimal performance and avoid potential compatibility issues, it’s best to use the sealant and tire specified by the wheel manufacturer.