Belt drives on bicycles are becoming increasingly popular. Particularly among bicycle tourists and commuters. This guide outlines the pros and cons of chain vs belt drive bikes to help you decide which drive system is best for your style of riding.
What is a Belt Drive Bicycle?
A belt drive bicycle uses a nylon toothed synchronous belt reinforced with carbon fiber cords to drive the rear wheel. The belt is used instead of the traditional bike chain. Belts are paired with durable stainless steel cogs and alloy chainrings. The result is an incredibly tough, clean, and long-lasting drive system that requires very little maintenance. This is the same belt technology that is used in belt drive motorcycles and auto racing engines.
Belt driven bicycles are very popular among commuters for their low maintenance requirements and cleanliness. Bicycle tourists and bikepackers are switching to belt drives due to the long maintenance intervals.
Belt Drive Pros
- Less maintenance- This is the main reason to make the switch. Belt drives are practically maintenance-free. You don’t need to periodically lube them or adjust them. All they need is a quick scrub down if they get caked with dirt mud. They just keep on working.
- Belt drives last longer than chain drives- A properly maintained belt drive can last 3-5 times as long as a chain drive. Some riders have gotten 20,000 miles (around 30,000 km) out of a single belt. Most chains only last 3000-5000 miles.
- Cleaner- Belt drives require no lubrication. This means you don’t have to get your hands dirty to clean and oil them. Because belts aren’t coated in lube, they don’t get caked with mud or sand as easily. Having said this, some cyclists do choose to apply a bit of silicone lube to the belt. This lube can make the belt last longer and run a bit smoother but is generally not required.
- Quieter- Belt drives operate almost silently. This allows you to hear the birds, cars, the wind, and everything going on around you. Chains make some mechanical noise. Particularly when switching gears with a derailleur.
- Lighter- The belt only weighs about 87 grams. A standard bike chain weighs around 300 grams. There is also less gear that you have to carry. For example, while touring with a belt drive, you don’t need to carry a chain breaker, extra links, chain lube, degreaser, or chain cleaner. This cuts a significant amount of weight and bulk from your toolkit. Having said this, internal gear hubs are heavier than derailleurs. Everything considered, you’ll save around 100 grams by switching to a belt drive.
- Mechanically simpler- The belt itself has no moving parts. They are manufactured in one loop. There are no pins or rollers or plates to stretch or wear out like there are on a bike chain. Of course, you will have to use an internal gear hub if you want gears with your belt drive. This adds more complexity than derailleurs.
- Less loss of efficiency over time- Belt drives don’t stretch or wear like chains. They keep their shape much better over time. The cog and chainring also wear at the same rate as the belt. This means the drivetrain stays efficient over the lifespan of the belt. Chains, on the other hand, tend to stretch and wear. They also wear at different rates than the cassette and chainrings. As these parts wear, they become less efficient.
- The driveline is always straight- The most efficient driveline is a straight line between your front chainring and rear cog. With a belt drive, the driveline is always straight because the belt never moves between cogs. The shifting all happens in a hub or gearbox. A chain often runs at an angle. This happens when you’re running toward the high or low extremes of your gear range with a derailleur setup. This is inefficient and wastes energy. Of course, if you’re running an internal gear hub or Pinion gearbox with a chain, the driveline is straight as well.
- No corrosion- Belts are made of modern synthetic materials including nylon and carbon fiber. These materials don’t rust. This property makes belt drives a great choice for areas where corrosion is common, like near the ocean for example.
- Belts are more efficient than chains at higher power outputs- If you are a particularly powerful rider, you might see an increase in efficiency at power outputs over 212 watts. For more info, check out this excellent article about the efficiency of belt drives from Cycling About.
- Belt drives are modern and high-end- If you’re the type of cyclist who likes to use the newest and most cutting-edge equipment in the sport, belt drives offer that.
Belt Drive Cons
- Belts are only compatible with an internal gear hub, Pinion gearbox, or single speed- Belt drives are not compatible with derailleurs because the belt can’t run at an angle. It must run in a straight line. This limits your drivetrain options.
- The frame must be compatible- Belt drive compatible bike frames must have a split somewhere in the rear triangle so the belt can be installed. This is necessary because a belt is one continuous loop. It can’t be split apart to install like a chain. Another consideration when choosing a belt drive compatible frame is stiffness. If the frame flexes too much, the belt will skip when under load. Your frame also needs to a belt tensioner. These come in three varieties, eccentric bottom bracket (EBB), sliding dropouts, or horizontal dropouts. I’ll talk more about belt compatible frames later on in this guide.
- Belt drives cost more than chain drives- A new belt will cost you $80-$100. A new front and rear sprocket will cost around $60-$80 each. In addition, you’ll need an internal gear hub. That can cost anywhere from a few hundred to well over $1000 for a high-end option like Rohloff. You could buy a whole new derailleur groupset for the price of replacing your belt and sprockets. Of course, a belt drive lasts much longer than a chain drive. If you consider this, the costs are much closer.
- Spare parts are harder to find- If you’re riding in the developing world or somewhere remote, finding a replacement belt or sprocket will be difficult or impossible. Many small bike shops and department stores don’t stock parts for belt driven bikes. You might have to order replacements online or find a high-end bike shop. Some countries don’t even import belt drive bike parts. If your belt drive system fails while touring somewhere very remote, you might have to fly home to buy the parts you need. Having said this, because of the long service life of belt drive, you can usually get away with just carrying a spare belt. The sprockets are very durable and last many thousands of miles.
- Belts are less efficient at low power inputs- If you’re just cycling casually, you’ll burn more energy while riding a belt drive bike vs a chain drive.
- Belt drives may cause the bottom bracket and rear hub to wear out faster- This happens because belts run at a much higher tension than chains. This extra tension puts more stress on the bearings in the bottom bracket and rear hub, causing them to wear out faster.
- You might be stuck in the event of a catastrophic failure- If you got a bad belt or your belt gets cut or damaged in an accident, you’ll need a replacement. You can’t fix a broken belt to limp your way home like you can with a broken chain. If you’re riding somewhere belts aren’t available, you might be out of luck. This failure can put a pause on your tour until you are able to secure a replacement.
- You can’t easily change your gear ratio by installing a new chainring or rear cog- Belt lengths are set. They are not adjustable. If you want to change your gear ratio, you’ll need to buy a new belt that is the proper length.
- Belts can limit your tire size or rim width- Because belts are wider than chains, you may experience some clearance issues. If you tire or rim is too wide, the belt might rub. This limits your tire width on some frames.
- Belts are not compatible with most full-suspension bikes- Many bike suspension systems change the effective chainstay length as they compress. Belts need to stay at the same tension and cannot tolerate this movement.
Chain Drive Pros
- Chains are compatible with every bike frame- Chains are the standard bicycle drive system. Every frame is designed to work with them. You don’t need any special features like a split in the frame, tensioner system, or extra stiffness.
- Cheaper- A new chain costs around $10-$20. A new cassette costs $20-$40. A chainring costs $20-$80. You could replace all three for less than the cost of a single carbon belt. Derailleurs are much less expensive than internal gear hubs as well. If you’re on a budget, a chain drive is your cheapest option.
- Chains are compatible with derailleurs- Derailleurs are the simplest, cheapest, and most common bike gear system. If you want to use a derailleur, you have to use a chain drive.
- Spare parts are easier to find- Every bike shop sells chains, freewheels, cassettes, and chainrings. If your chain breaks or a cog wears out, you can easily find a replacement almost anywhere. Even in remote parts of the world. There is an exception to this. If you decide to use a modern 9, 10, 11 or 12 speed groupset, parts can be hard to find. Many bike shops in developing countries don’t carry parts for these systems yet. The chains are much more narrow and are not cross-compatible with larger chains. If you’re choosing a chain drive to make finding parts easier, 6, 7, or 8 speed is your best bet. These are available everywhere.
- Chains are more efficient at low power inputs- For casual cycling, you’ll burn slightly less energy by using a chain drive.
- Bottom bracket and rear hub bearings last longer- Chains run at a lower tension than belts. This puts less stress on the bearings so they don’t wear as quickly.
- Chains are easy to adjust- If you decide to switch to a different size chainring, you can easily adjust the length of your chain to fit the new one. You don’t need to buy a new chain. Belt lengths are set when you buy them. There are a set number of lengths available.
- Chains are easy to service and replace- Every bike mechanic knows how to set up a chain drive and maintain it. A belt drive is a bit more modern and complex. It takes more know-how to properly set it up.
- You can repair a chain in the field if it breaks- Bike chains rarely catastrophically fail. If the chain breaks or gets bent, you can almost always remove a few links and limp your way to the nearest bike shop. You might need to run single speed if you do this but at least you can ride. Of course, you’ll need a chain tool to make this repair.
- Chains are compatible with full suspension- With most full-suspension bikes, the effective chainstay length changes as the suspension travels. The rear derailleur can compensate for that change by changing the length of the chain. This is accomplished with springs in the derailleur which keep the chain at the proper tension. This isn’t possible with belt drives.
- Chains are standard- The roller chain has been around since the 1880s. This means bicycles have been using chain drives for over 100 years at this point. The technology is tested and proven.
Chain Drive Cons
- More Maintenance- To keep your chain running smoothly, you have to keep it clean. This involves scrubbing off the grease and dirt then applying some new lube. It’s about a 10-15 minute job. A casual cyclist will have to clean and lube their bike chain about once per month. If you’re touring, you might need to clean your chain every couple of days. Belts operate pretty much maintenance-free.
- Chain drives don’t last as long- An average bike chain lasts around 3,000-5,000 miles if it’s properly cared for. Every other time that you change your chain, you’ll probably have to replace your cassette. Belt drives can last 10,000-20,000 miles before they need to be replaced. One way to extend the life of your chain drivetrain is to swap chains every 500 miles or so. Some riders have 4 chains that they rotate between. The idea behind this is that your cassette will wear more evenly and last longer. After the chains and your cassette wear out, you replace everything. You might get 10,000 miles out of your chain drivetrain this way. Of course, you’re still using multiple chains.
- Chains lose efficiency over time- As chains wear, they tend to ‘stretch’. This stretching is really the loss of material on the chain from wear. As chains wear out, they become loose. This reduces tension and can lead to slippage. Cogs can also wear down to a point that the chain doesn’t fit quite right. This can create additional friction which causes inefficiency. Not cleaning and lubing the chain often enough also reduces efficiency. This costs you energy. Belts maintain their shape and wear much more slowly. They also wear at the same rate as the cogs. This means they maintain their efficiency longer.
- Dirtier- Chains require frequent cleaning and greasing. It’s a messy job. While dealing with your chain, you’ll eventually get grease on your hands and gear.
- Heavier- A chain weighs over three times as much as a belt. For example, an average 9 speed bike chain weighs around 300 grams. A Gates Carbon Drive belt weighs around 87 grams. When you’re touring, you’ll also need to carry a chain tool, lube, spare links, and something to clean with. Maybe even an entire spare chain. This adds a significant amount of weight. With a belt drive, all you’ll need is a spare belt.
- Chain drives are louder- The metal chain running against metal cogs makes some noise. Shifting gears also produces a bit of noise. The noise is amplified if the chain is dirty, worn out, or out of adjustment. Belt drives are almost silent. A perfectly cleaned and adjusted chain is very quiet as well.
- Chains corrode- Because chains are made of metal, they tend to rust. This is particularly common if you ride near the ocean or during the winter in an area that salts the roads. Belts, being made from synthetic materials, don’t rust.
- Chains are more mechanically complex- Chains have a lot of moving parts. Each link has pins, outer plates, inner plates, and rollers. If a part gets bent or gummed up, it can prevent your chain from working properly. Belts are simply one continuous piece of material. Having said this, if you’re using derailleurs, your drive system is less complex than if you use an internal gear hub.
- The driveline isn’t always straight- When you use a derailleur, the chain runs at an angle much of the time. Particularly when you’re riding at an extreme of your gear range. Running your chain at an angle is inefficient because the angle creates more friction in the drive system. Of course, this isn’t a problem if you use an internal gear hub or run single speed because your chainline will always be straight.
More Cycling Pros and Cons Analyses from Where The Road Forks
- Drop Bars Vs. Flat Bars
- Bikepacking Bags Vs. Panniers
- Flat Pedals Vs. Clipless
- Disc Brakes Vs. Rim Brakes
- Tube Vs. Tubeless Bicycle Tires
- Internal Gear Hub Vs. Derailleur
- Steel Frame Vs. Aluminum Frame
- Presta Vs. Schrader Valves
A Few Things to Consider When Choosing a Belt Drive Compatible Bike Frame
In order to install a belt drive, your frame must be compatible. A few years back, these frames were pretty rare. These days, with the increase in popularity of belt drives, manufacturers are introducing more and more belt compatible frames. Below, I’ll outline three requirements your frame must meet to use a belt drive.
Belt Drive Frame Splitters
In order to install a belt drive, your frame must split somewhere in the rear triangle. This is necessary because a belt is one continuous piece of material without any breaks, unlike a chain. This split can be in the seatstay, chainstay, or dropout. These days, most frame splitters are integrated into the dropout.
Before belt drives were common, people would modify their frame with a splitter so they could upgrade without having to replace the whole frame. This involved cutting a break in the rear triangle and bolting it back together. Some kind of rod would be installed inside the tube for extra strength. Check out this article from Green Bird for some pictures of DIY frame splitters.
The problem with modifying your frame is the potential loss of stiffness in the rear triangle. This is a problem because belts need to run at a much higher tension than chains to prevent slippage. When you modify your frame, there is no guarantee that it will be stiff enough to hold the belt in place. If the frame flexes too much, the belt slips.
If you’re in love with your frame and you want to take the chance, there are frame builders who can make the modification. Keep in mind that this will be a pretty expensive modification.
The best option is to switch to a dedicated belt drive frame. This way, you know for sure that the system will work as expected. Belt compatible frames are common these days.
If you want to do a belt drive conversion but you don’t want to modify your frame, there is a company that makes belts with a split in them called Veer Cycle. I’m not sure how these compare strength wise to standard non split belt drives like the ones from Gates. Comment below if you have any experience with these. I’d be interested to hear how they work.
In order to use a belt drivetrain, you need to be able to adjust the belt’s tension. There are three different options for belt tensioning. Each has its benefits and drawbacks.
1. Eccentric bottom bracket (EBB)
An eccentric bottom bracket is a device that installs in the bottom bracket shell of your frame. It allows you to adjust your crankset forward and backward about 14 mm to adjust the tension of your belt.
As an added benefit, eccentric bottom brackets allow you to adjust your crankset up and down. Raising your crankset gives you more clearance off-road. Lowering your crankset is preferable for road riding. There are two types of eccentric bottom bracket.
- The first style works as an adapter. You tighten the EBB unit into the bottom bracket shell then install a threaded bottom bracket into it. To adjust the EBB, you loosen a couple of bolts then rotate the whole unit in the bottom bracket shell of your frame. You then re-tighten the bolts to set the unit in place at your desired tension and height.
- The second style of eccentric bottom bracket integrates everything into one unit. This includes the bearings. You simply tighten the unit into the bottom bracket shell then install your integrated spindle crankset. You adjust the unit by loosening a couple of bolts, rotating the unit, then re-tightening the bolts at the proper tension.
The main benefit of using an eccentric bottom bracket is that they fit in almost every frame. They also help maintain rear triangle stiffness because there are no changes to the dropouts. They also allow you to remove your rear wheel without having to re-adjust the belt tension.
The biggest drawback to eccentric bottom brackets is that they can be a bit creaky. They don’t feel quite as solid as a standard bottom bracket. Another problem is that they require a bit of maintenance. The reason is that water and debris can enter. This needs to be cleaned out periodically.
For more info, check out this excellent guide to eccentric bottom brackets.
2. Sliding Dropouts
Sliding dropouts allow the dropout itself to move forward and backward. These allow about 20 mm of adjustment. To adjust the belt tension, you simply turn a bolt that slides a part of the dropout that holds your wheel forward and backward. Most designs use a couple of lock nuts on the sides of the dropout to lock it in place once your belt is set to the correct tension.
The beauty of sliding dropouts is that the design allows you to remove your rear wheel without having to re-adjust the belt tension. The wheel slots in and out without any adjustment to the position of the dropout. This makes repairing a flat much easier. When you replace the wheel in the dropout, the tension stays the same. Sliding dropouts are also very easy to use.
The only problem with sliding dropouts is that some designs tend to lose tension over time. This is particularly common on lower-end frames. When this happens, have to re-tension the belt.
3. Horizontal Dropouts
This design is similar to sliding dropouts. The difference is that the wheel slides in the dropout rather than a part of the dropout itself. This is the least common belt tensioning design. It doesn’t really offer any benefits over the other belt tensioning designs.
The biggest drawback to horizontal dropouts is that you have to re-adjust the belt tension each time you remove your rear wheel. This gets pretty tedious. Gates, one of the leading belt drive manufacturers, does not recommend this design for their belt drives for this reason.
Belt Drive Frame Stiffness
For your belt drive to work as intended, your frame needs to have a stiff rear triangle. This is particularly important for powerful cyclists, heavy cyclists, or those who carry luggage. The reason that rear triangle stiffness is so important is because belts tend to skip when the frame flexes. This happens because the belt loses tension when the frame flexes.
If your frame isn’t quite stiff enough, you can increase the tension of your belt. This reduces the likelihood of skips. Unfortunately, an overly tensioned belt also reduces the efficiency of your drive system.
Stiff frames, on the other hand, allow you to run your belt at a lower tension. This eliminates skips and improves efficiency. When shopping for a frame, look for oversized chainstay and seatstay tubes. These help to strengthen the rear triangle.
One of the most popular belt drive systems is the Gates Carbon Drive. If you plan to use this system, consider checking out Gates’s list of compatible frames. These have been tested and approved for using belt drives.
Belt Drives and Gearing
One of the biggest drawbacks of switching from a chain drive to a belt drive is that you limit yourself to internal gear hubs, crank-based gearboxes like those from Pinion, or single speed. Derailleurs are not compatible because the belt can’t operate at an angle. The belt must stay in place and run in a straight line between the cog and chainring.
Before purchasing your drivetrain components, you’ll want to make sure that they have the same beltline. Generally, the placement of the rear cog is set and cannot be adjusted. Cranksets can usually be adjusted a few millimeters closer and further from the frame.
For example, if your Rohloff internal gear hub has a beltline of 54.7 mm, you’ll want to purchase a crankset that has a beltline of 54.7 mm. You can probably get away with 1 mm difference.
For more info, check out this great guide to chainlines from Sheldon Brown. This guide explains how to measure chainlines and make minor adjustments.
A Note About Belt Drive with Rohloff Hub
This combination is a dream for many cyclists. In order to maintain the warranty for your Rohloff hub, you’ll have to meet a couple of conditions:
- Your frame must be stiff enough- Bike frame manufacturers must test their frames to prove that they are strong enough to support the tension of a belt drive. This involves a specialized testing jig. Frames that pass the test will be advertised as ‘belt drive ready’ or some equivalent advertising term. Alternatively, you can check out Gates’ list of approved frames linked above.
- You must use a belt snubber- This device prevents the belt from skipping on the rear sprocket or sliding off the cog. This can happen when the belt is under insufficient tension or under a particularly high load. The snubber also helps to protect your belt from damage from lifting off of the cog. Rohloff requires the use of a snubber on their hubs.
Belt Drive with Pinion Gearbox
If you’re not a fan of internal gear hubs, Pinion offers a unique alternative. These hubs mount at the crankset to specially designed frames. These gearboxes are designed for use with a belt drive. They offer a wider range of gearing than most other drive systems. The main drawbacks are the cost and weight.
The belt tension depends on several factors including how powerfully you pedal, frame stiffness, and whether you use an internal gear hub or single speed. To tension your belt properly, you’ll need some way to measure the tension. For this, you have two options:
- Smartphone app- Gate’s free iPhone and Android app measures your bike’s belt tension with your phone’s microphone. All you have to do is tell enter the size of your front and rear sprocket as well as your belt then hold your phone next to the belt and give it a few of plucks. As the belt vibrates, it will send out sound waves. Your phone measures the frequency of the waves to determine the tension of your belt. You can use this information to tighten or loosen your belt until it’s at the ideal tension. You can get the Android app here and the iPhone app here.
- Belt tensioning gauge- This tool can give you a more accurate measurement than a smartphone app. You can buy the Gates Tension Gauge on Amazon.
Exactly how you tension your belt depends on the type of belt tensioner that your bike uses. Usually, all you’ll need is an Allen key and a wrench. Eccentric bottom brackets sometimes require some kind of spanner to turn them. The sizes depend on your setup.
A Note About Handling Carbon Belts
Belts are a bit more fragile than chains. If you mishandle them, you can damage the internal carbon fiber. If this happens, the belt can snap. You never want to crimp, twist, invert, backbend, zip tie, or use your belt as a wrench. When installing a belt, set your chainring and rear cog so they are close together. You don’t want to try to stretch the belt onto the gears.
If you’re touring and need to carry a spare belt, gently fold it into three loops and try to store it somewhere where it won’t get crushed. Try to be careful while folding and unfolding it to prevent damage.
Final Thoughts: Chain Vs Belt Drive
As you can see, chains and belts both have their benefits and drawbacks. Both systems are reliable, durable, and efficient. The main differences are the cost and amount of maintenance that is required. In the end, the choice comes down to personal preference and your riding style. Hopefully, this guide helps you decide.
Where do you stand on the chain vs belt drive debate? Share your experience and tips in the comments below!
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