Carbon belt drive has been developed over the past 30 years into a high-performance power transmission system. It is used not only in cycling, but also in applications such as driving blowers in 10,000-horsepower racing engines, powering 150-horsepower motorcycles, and more recently, in bicycle drivetrains.

The belts consist of a continuous loop of polymer with moulded nylon teeth, reinforced by multiple carbon fibre tensile cords. These are paired with stainless steel rear cogs and durable alloy front chainrings, creating a robust drivetrain alternative capable of operating in temperatures ranging from -65°F (-53°C) to +185°F (+85°C).

Belt drive systems are valued for their low maintenance requirements and typically offer 3-4× the service life of a traditional chain. However, their adoption is limited by the fact that belts cannot be used with derailleur systems. Instead, they rely on internally geared hubs such as Rohloff or Shimano hubs, or gearboxes like the Pinion P1.18.

I’ve personally been using belt drivetrains paired with Rohloff 14-speed hubs since 2010. That includes a 31,000 km (19,000 mi) ride from Europe to Australia, a current 45,000 km journey from Argentina to Alaska, and numerous multi-month tours in between. My experience began with a modified Surly Bikes touring bike, later moved to a custom Co-Motion tandem, and now continues on a KOGA WorldTraveller-S touring bike.

Note: This article was originally published in May 2012 but has been completely overhauled Feb 2019.

Why Use Belt Drive?

Belts have a long service life
A properly maintained belt drivetrain can last well beyond 30,000 km (19,000 mi). Unlike chains, belts do not rust, even with frequent exposure to rain or salt, making them particularly well-suited to coastal or all-weather riding.

Belts require little to no maintenance
There’s no need for lubrication or degreasing. Maintenance is typically limited to occasional cleaning with water and a brush to remove dirt or grit buildup.

Belt drivetrains are silent
A well-tuned chain is quiet when freshly cleaned and lubricated, but a belt is typically that quiet all the time. In most conditions, the drivetrain produces little more than a faint hum, with only occasional need for silicone treatment.

Belts are marginally lighter than chains
In many setups, belt systems can save around 100 grams compared to a chain drivetrain. See my drivetrain weight comparison HERE.

Are There Any Downsides?

You need a belt-compatible frame
Because belts are a single continuous loop, the frame must include a split in the rear triangle to allow installation. It also needs to be designed with sufficient stiffness and proper alignment so the belt stays securely on the rear sprocket. A stiffer rear triangle can even allow for lower belt preload, which reduces drivetrain resistance.

Belts are less efficient than chains at low power outputs
At lower rider inputs, belts tend to show slightly higher friction than chain drivetrains. However, this gap narrows quickly with increasing power, and in dirty or muddy conditions, belts may actually have an advantage because they shed grit far more effectively than a chain’s many moving links.

Replacement parts are not commonly stocked in shops
Belt components are less widely available in local bike stores. That said, given their long service life, replacements are rarely needed. For long tours, carrying a spare belt (around 87 grams) is a sensible precaution; it packs small and can be a trip-saver. In contrast, chainrings and cogs are rarely carried as spares due to their durability.

Higher upfront cost
Belt systems cost more initially than traditional chains. However, over their lifespan, the cost per kilometre can be very competitive. For example, over full use, belt drivetrains can work out to roughly 125 km per dollar. This is comparable to a chain system costing around $60 per 7,500 km (a typical upper lifespan for a high-performance chain).

Gates Belt Drive Models

CDX: High-Performance
The CDX High-Performance system is the most widely used belt drivetrain. It is commonly found on touring, trekking, and adventure bikes. The system offers a broad range of gearing options, including 16 belt lengths, 7 front sprocket sizes, and 8 rear cog sizes, giving riders a high degree of drivetrain flexibility.

CDX: EXP
CDX EXP is a newer, oversized version of the CDX system, featuring around 25% more contact surface area. It is designed to improve both durability and range, though it is still relatively uncommon on production touring bikes. The current range includes five front sprockets and four rear cogs.

CDN: Urban
CDN Urban is the entry-level belt system from Gates, designed to bring belt drive technology to city bikes in the €500 complete bike segment. It is intended for casual use and is not approved for mountain biking, mid-drive e-bikes, fixed-gear applications, or high-mileage touring.

There have been some reported issues with early CDN rear cogs, although many of these have since been replaced or upgraded to compatible stainless-steel CDX components for improved durability and reliability.

Rear Triangle Stiffness & Belt Drive Frames

One of the most critical requirements for a belt drivetrain is a sufficiently stiff rear triangle, especially on loaded touring or bikepacking setups.

On earlier belt-equipped touring bikes, frame flex was sometimes enough to introduce belt misalignment under high load, occasionally causing the belt to skip. However, on a more rigid frame like the KOGA WorldTraveller-S, even high pedalling torque with luggage has not produced any belt skipping, indicating a significantly improved level of stiffness.

A stiffer rear triangle also has an efficiency benefit. Because belt systems rely on higher baseline span tension than chains, a rigid frame allows the system to operate safely at lower preload tension. This helps minimise drivetrain resistance while maintaining reliable engagement.

Gates provides a “stiffness test approved” label for frames that meet its minimum requirements. However, this is only a baseline standard. In practice, some touring and trekking manufacturers exceed this threshold by a wide margin. Frames that use oversized chainstay and seatstay tubing generally perform best in this regard (I have an article on frame stiffness HERE).

Belt Drive Frames: Belt Tensioners

A belt drivetrain requires a method for setting and maintaining correct belt tension. There are three main frame design approaches, each with distinct advantages and trade-offs.

Eccentric Bottom Brackets (EBB)

Eccentric bottom brackets allow the crankset position to be adjusted—typically around 13 mm forward or backward—to fine-tune belt tension. They also offer the flexibility to run a slightly higher or lower bottom bracket height depending on terrain preference.

In practice, EBB systems can sometimes develop creaks on long rides and may require more maintenance. They can also be susceptible to water ingress, which can make adjustments more difficult in the field.

On the positive side, manufacturers such as KOGA have demonstrated that well-designed EBB frames can achieve very high rear triangle stiffness, which is beneficial for belt performance and efficiency.

Sliding Dropouts

Sliding dropout systems provide around 20 mm of adjustment and are generally very user-friendly. One of their key advantages is convenience: when removing the wheel, the belt can drop out and be reinstalled without needing to reset tension each time.

However, lower-quality implementations can sometimes allow the axle to shift forward under load, which can lead to insufficient belt tension if not properly designed or tightened.

Horizontal Dropouts

Horizontal dropout designs are less common for belt drive systems and are generally not recommended by Gates. This is because belt tension must be carefully reset each time the wheel is removed, which adds inconvenience and increases the chance of setup error.

If used, there must typically be at least 10 mm of adjustment remaining in the dropout slot after installation. This clearance is necessary to allow the belt to be fitted onto the chainring during wheel installation without excessive force or misalignment.

Belt Drive Frames: Splitters

Unlike a chain, a belt is a single continuous loop, so the frame must include a split in the rear triangle to allow installation. This “splitter” can be integrated into the seatstay, chainstay, or, more commonly, the dropout area.

The most widespread solution is a split built into the rear dropout system. However, some manufacturers have experimented with seatstay splitters in an effort to maximise rear triangle stiffness and maintain structural integrity under load.

In the past, some riders modified existing frames by adding splitters to convert them for belt use. This approach is generally no longer recommended, as it is difficult to guarantee sufficient rear triangle stiffness and long-term alignment accuracy once a frame has been altered.

Today, purpose-built belt frames are widely available at prices comparable to the cost of modifying and repainting a frame. As a result, dedicated designs are typically the safer and more reliable option.

If a modification is still being considered, it should only be carried out by an experienced and reputable frame builder with proven expertise in belt-compatible frame construction.

Belt Drive and Rohloff Hubs

Belt drive combined with a Rohloff hub is widely regarded as a highly durable and low-maintenance touring setup, but there are a few important requirements to ensure proper function and maintain warranty coverage.

First, the frame must meet a minimum rear triangle stiffness standard. Manufacturers typically verify this using a dedicated testing jig to achieve “stiffness test approved” status. A list of approved frames is available from Rohloff and partner manufacturers.

Second, the use of a belt snubber is strongly recommended. This component helps prevent the belt from riding up and off the rear sprocket under high load or when the belt tension is slightly low. If this happens, it can place stress on the belt’s internal carbon tensile cords, so a snubber adds an important layer of protection.

In earlier systems, belt sprockets were threaded directly onto Rohloff hubs. This has since been replaced with a more user-friendly splined carrier system (part #8540L), which supports interchangeable belt cogs in common sizes such as 19T, 20T, and 22T. This update significantly improves ease of maintenance and gear ratio changes.

There was a known issue with the first-generation splined carriers, but it was resolved in mid-2018, with updated components and warranty replacements issued. This is no longer considered a concern in current systems.

Belt Lines and Frame Clearance

A straight and precise belt line is essential for reliable belt drivetrain performance. Ideally, alignment should be within approximately ±1 mm. Because the rear cog position is usually fixed by the hub system, most adjustment is done at the crankset or chainring position.

Typical belt line values for common systems include:

• Shimano Alfine Di2: 39.8 mm
• Alfine 8 / 11: 43.7 mm
• Nexus 8: 44.35 mm
• Nexus 7: 43.05 mm
• Pinion C-Line: 52 mm
• Rohloff 148 mm (splined carrier): 51.7 mm
• Rohloff 135 / 142 mm (splined carrier): 54.7 mm
• Pinion P-Line: 56 mm
• Rohloff 170 / 177 / 190 / 197 mm: 72.2 mm

To achieve correct alignment, it’s important to check the chainline specification of the crankset you plan to use. For example, a triple 104 BCD crankset typically has a chainline of around 55 mm when the chainring is mounted in the outer position, which makes it a common choice for Rohloff-based belt setups.

Gates also produces cranksets with multiple belt line options (such as 39.8 mm, 43.7 mm, 45.5 mm, and 54.7 mm) to better match different hub systems and frame geometries.

Another important consideration is chainstay clearance, particularly when using Shimano hub systems. Because the gear selector mechanism is external on the drive side, it can create tight clearance constraints. If a frame does not provide sufficient space between the chainring and chainstay, compatibility issues may arise. In these cases, it is advisable to confirm clearance with the frame manufacturer before committing to a build.

Gear Ratios

You might assume that fixed belt lengths would significantly limit gearing options, but in practice, the system is quite flexible. With multiple belt lengths available, along with a range of compatible chainring and rear cog sizes, the resulting gaps between usable gear ratios are relatively small.

The Gates Calculator (also available as a smartphone app) is a useful tool for selecting compatible combinations. By entering your frame’s effective chainstay length (for example, 460 mm) and selecting “Find Solutions”, it will generate all viable belt, chainring, and cog pairings that fit your frame geometry first. From there, you can refine the options based on your preferred gear ratio and intended terrain, in line with the available components for systems such as Rohloff, Shimano, or Pinion.

As noted earlier, if you are using a belt drivetrain with horizontal dropouts, there must be at least 10 mm of adjustment remaining in the dropout slot once the belt is installed and tensioned.

Belt Drive and Tandems

Gates belt drives can also be used on tandem bicycles, primarily as a timing belt system between the front and rear cranks. This setup typically offers a small weight saving of around 250 grams compared to an equivalent chain and chainring arrangement.

For proper function, tandem frame geometry is important. The boom tube must be designed to accommodate a precise bottom bracket spacing, typically around 724 mm between the two bottom brackets. In addition, compatible cranksets with a 130 BCD standard are generally required to ensure correct belt alignment and fit.

It is technically possible to run belt drives on both the timing (non-drive) side and the main drivetrain (drive side) of a tandem. However, in most practical setups, using a belt only for timing is the preferred and more common configuration due to simplicity and compatibility considerations.

Maintenance and Cleaning

Gates belt drivetrains are often described as nearly maintenance-free. In most cases, cleaning is straightforward: a rinse with water and a quick brush—such as an old toothbrush—is usually sufficient. There is no need for degreaser, chain cleaners, or handling oily components.

Actual maintenance needs depend heavily on riding conditions. In very dry and dusty environments, a light application of silicone lubricant may be required every few days. In contrast, in cleaner or wetter conditions, it can often be months between any meaningful maintenance. While belt systems generally shed mud and grit effectively, keeping the tooth profiles clean helps maintain optimal efficiency and lifespan.

When lubrication is needed, a general-purpose silicone spray is typically used at the first sign of squeaking. These products are widely available, including automotive-grade sprays found in many parts of the world. Gates also recommends specific heavy-duty silicone lubricants designed for belt drive applications.

Handling Belts

Gates belts require careful handling to avoid damaging the internal carbon fibre tensile cords. Excessive twisting, sharp bending, or compressive force can compromise the structure, so the key principle is to avoid stressing the belt in any unnatural direction. For long-term storage, it is best to keep the belt fully relaxed and uncoiled.

When installing a rear wheel, the belt should not be forced or “cranked” into place as you might with a chain. Instead, it should be positioned onto the front chainring and rear cog first, and then the wheel is inserted into the dropouts while maintaining alignment.

One advantage of belt systems is portability. They coil compactly and are easy to carry as a spare on long trips. A spare belt can typically be stored in a pannier pocket without issue. However, care is still required when folding and unfolding it. Sharp bends should be avoided, and the belt should be allowed to form a natural coil. When correctly packed, it will typically settle into a smooth loop that folds into roughly three relaxed sections.

Tensioning Belts

Gates Carbon Drive belt tension varies depending on the drivetrain setup (singlespeed or internally geared hub) as well as rider power output. Achieving the correct tension is important, and there are several methods to measure it.

Smartphone app method
A simple smartphone app can be used to estimate belt tension by measuring vibration frequency. You hold the phone near the belt, pluck it lightly, and the app calculates an average frequency based on the sound.

Dedicated tension tools
More precise tools, such as a Sonic Tension Meter or Krikit gauge, are available from specialist bike shops. While these offer higher accuracy, many users find they are not strictly necessary for routine setup and maintenance.

Checking for variation (tight spots)
Belt tension can vary slightly as the crank rotates. For this reason, multiple measurements should be taken at different crank positions, with the results averaged. A variation of around 10 lb or 15 Hz is generally considered acceptable. If variation exceeds this significantly, it is recommended to check alignment and ensure the chainring is properly centred on the crank spider.

Cost

CDX: High Performance
Chainring: US $70-110
Rohloff Cogs: US $93-105
Alfine Cogs: US $120-125
Pinion Chainring: US $154
Pinion Cogs: US $128-140
Belts: US $80-105

Kit Total Rohloff: from US $243
Kit Total Alfine: from US $270
Kit Total Pinion: from US $362

Belt Drive Touring Bike Manufacturers

Like the sound of belt drive? I’ve compiled a list of touring bike manufacturers HERE.

For those wanting to do a custom build, my list of touring frame manufacturers is found HERE. Expect to spend more than US $1000 / €1000 on a complete belted bike and a minimum of US $500 / €500 on a belted frameset.