What is a drivetrain on a bike and why is it so important?
If you’re interested in the mechanics of how a bike works, you’re in the right place. In this blog, we’re talking about all things drivetrain – the powerhouse of the bike.
Discover everything you need to know about the drivetrain, including what components make it up, how it works, and how to clean and fix it if it breaks.
Table of contents
- What is a bike drivetrain?
- What parts make up the drivetrain on a bike?
- How to fix a bike drivetrain
- How often should I clean the bike drivetrain?
- How to clean the bike drivetrain
What is a bike drivetrain?
The drivetrain is one of the most crucial elements of a bike – it’s what makes it go! As you pedal, the drivetrain transfers the power from your legs and feet and turns the wheels to make you go forward. Additionally, it allows you to change gears to make your cycling easier or harder on various gradients.
It’s important to know that the drivetrain, with the shifters and brakes, are part of the groupset – the components that help you to stop and go. Although the shifters are not part of the drivetrain, they control the gear changes.
What parts make up the drivetrain on a bike?
The drivetrain includes components that work together to enable you to change gears and go forward. Typically, it consists of one or two derailleurs, a chain, the cassette and a crankset.
The crankset
The crankset, or chainset, is at the centre of your drivetrain and bike. As you pedal, the crankset moves, transferring force from your legs to the rest of the drivetrain and your back wheel.
The crankset includes two crank arms, attaching to the pedals with chainrings, which the chain runs over.
The bottom bracket bearing allows the crankset to rotate smoothly and freely. It also typically includes an axle or spindle that holds the crankset together.
The chainrings
The chainrings are part of your chainset and are your front gears. They consist of teeth that hold the chain in place. Bikes will typically feature one to three chainrings.
If you’re building a bike from scratch or purchasing a new bike, consider the gear range you want to suit your cycling discipline.
Chainrings come in various sizes to suit different disciplines, determined by the number of teeth (T).
Most gravel and mountain bikes feature 1x drivetrains rather than 2x, which typically feature on road bikes. A 2x drivetrain has two chainrings and a front derailleur, whereas a 1x drivetrain doesn’t have a front derailleur and only has a single chainring.
A 1x drivetrain saves weight with fewer components, and there is no need for a gear cable or electrical wire routing from the shifter.
The cranks
The crankset features two crank arms which attach the pedals to the drivetrain. Cranks can be of different sizes. Longer length gives you more leverage.
You will typically get longer cranks on larger bikes for taller people. However, leg length can also vary in height, so keep this in mind when choosing crank length.
The front derailleur
The front derailleur is the component that moves the chain between the chainrings on the crankset. It derails the chain from one chainring and pushes it on another. You can control the front derailleur using the left shifter.
There are two ways to mount front derailleurs: band-on and braze-on. Band-on front derailleurs have a metal hinge that fits around the seat tube, whereas braze-on front derailleurs fix to a mounting plate riveted onto the drive-side face of the seat tube.
If replacing a front derailleur, stick to the manufacturer and series to ensure compatibility.
The rear derailleur
The rear derailleur is the mechanism that shifts the chain on the cassette to change the bike gears. Controlled by the right-hand gear shifter, you can switch between typically 7 to 13 speeds.
All rear derailleurs feature a cage that houses pulley wheels that the chain wraps around. Some feature chain retention methods, such as a clutch mechanism, preventing the chain from slapping on the drive-side chainstay, which is particularly helpful for off-road cycling.
Rear derailleurs typically attach to the bike’s frame by a derailleur hanger using a single bolt.
If you’re replacing the mechanism, keep the same manufacturer groupset and series your bike has because the shifter cable pull is specific for every rear derailleur.
The cassette
The cassette is a cluster of sprockets mounted on the rear wheel. The rear derailleur moves the chain up and down these cogs. You can get a wide range of sizes to suit all riding disciplines. You can determine the size by expressing the smallest and largest cog by the number of teeth.
Cassettes can have between 7 and 13 sprockets, depending on the intended use and manufacturer. Gravel and mountain bikes tend to have a wider-ranging cassette than road bikes due to the 1x drivetrain, providing easy gearing to winch itself up steep hills. However, it still needs a big enough cassette for fast riding on flat and downhill stretches.
The cassette fits on the freehub of the wheel. You’ll find notches that align with splines on the freehub inside the cassette. Manufacturers have different spline and cassette designs. So always check you have a matching cassette and freehub when buying new parts.
The chain
The chain is the component that passes through all the drivetrain components above. It’s a series of links featuring alternating wide and narrow links throughout its length.
Different chain lengths have different speeds, so ensure you have the correct chain for the number of speeds your groupset has. You can do this by checking their compatibility.
How to fix a bike drivetrain
As the drivetrain consists of several moving components, a few common issues occur with drivetrains. Here are the eight most common drivetrain issues and their fixes.
1. A skipping chain
Issue: If your chain is randomly skipping gear, there may be a misalignment in your derailleur, you have worn out your cassette or chainrings, or your chain has stretched.
Fix:
- Check for wear on your cassette and chainrings. If there is wear, consider replacing them.
- If your derailleur isn’t aligned correctly, adjust the screws and cable tension.
- Check the chain for wear using a chain checker and replace it if it has stretched.
2. A noisy drivetrain
Issue: The cause of a noisy drivetrain is a lack of lubrication or dirt on the chain or drivetrain components.
Fix:
- Clean the chain, cassette and chainrings thoroughly using the method below
- Apply lubricant to your chain.
3. The chain is rubbing the front derailleur
Issue: If the chain rubs the front derailleur, there could be a misalignment or incorrect adjustment.
Fix:
- Adjust the limit screw on the front derailleur and test every gear to make sure it doesn’t rub.
- Check the height and angle of the front derailleur to ensure the chainrings align with it.
4. The chain is slipping or dropping
Issue: Worn chainrings, a bent derailleur hanger, or incorrect derailleur adjustment can cause the chain to slip and drop.
Fix:
- Inspect and replace worn chainrings
- Replace the derailleur hanger if it is bent and misaligned.
- Adjust the front derailleur if it is misaligned.
5. Difficulty shifting gear
Issue: If you’re having difficulty shifting gears, it may be a cable tension issue, worn cables or worn shifter components.
Fix:
- Check and adjust the cable tension at the derailleur and shifter.
- Replace worn cables and housing.
- Clean and replace shifter components if worn.
6. Stiff or inconsistent shifting
Issue: If you have stiff or inconsistent shifting, you could have dirty or sticky cables, worn pulley wheels or a misaligned derailleur.
Fix:
- Clean or replace cables and housing.
- Lubricate your pulley wheels and pivot points on the derailleur.
- Ensure your derailleur hanger is straight and aligned.
7. Creaking noises
Issue: If you can hear creaking noises, it could be a loose or dry bottom bracket, pedal or chainring bolt.
Fix:
- Check and tighten all bolts on the crankset, bottom bracket and pedals.
- Apply grease to the threaded interfaces.
8. Chain tension issues (single-speed bike)
Issue: If you’re having chain tension issues on your single-speed bike, you may have the incorrect tension or your chain may be worn.
Fix:
- Adjust the chain tension.
- Or replace it if it is too worn.
How often should I clean the bike drivetrain?
The frequency of when you should clean your bike drivetrain depends on various factors like riding conditions and weather. However, the consensus is you should clean and lubricate it every 100-200 miles or more often if you’re riding in muddy conditions.
For example, if you frequently ride in wet or muddy conditions, you need to clean your drivetrain more often because the build-up of mud and grime can degrade the drivetrain’s functionality.
It will also depend on the type of lubricant you use. Some lubricants last longer than others. If you’re using a dry or wax lubricant, you may need to reapply more frequently. Equally, lubricant for wet weather can accumulate more dirt, so continue to monitor the dirt build-up on your drivetrain to determine when you clean it.
Some cyclists like to keep their drivetrain meticulously clean, while others are more lenient. But regular cleaning and maintenance will help it last longer and ensure the component’s smooth operation.
How to clean bike drivetrain
If you have yet to clean your drivetrain, follow the step-by-step guide to maintain your drivetrain and make your components last.
You will need:
Steps:
- Firstly, use a brush or old rag to remove excess dirt and grime from the chain, cassette and chainrings.
- Then, apply the degreaser to the drivetrain components. Allow this to sit for a few minutes to help break down the accumulated grease.
- Use the brush to scrub the embedded dirt thoroughly. Ensure to get between the hard-to-reach places.
- Rinse the drivetrain components with mild, soapy water to remove the degreaser and loosened dirt. Never use high-pressured water directly on the bearings, as it can force water into small areas, which can cause rusting.
- Allow the drivetrain to dry completely.
- Lastly, apply lubricant to the chain, ensuring to coat each link. Then, wipe off any excess lubricant.
Regularly maintaining, cleaning and well-lubricating your drivetrain will prolong its life, ensuring smoother shifting and a more enjoyable experience.
Drivetrains at Swinnerton Cycles
There you have it! Everything you need to know about the drivetrain. Knowing all you can about how your bike works will help you to maintain it properly, diagnose issues and extend the life of your bike.
If you’re keen to start a bike build project or replace any broken parts on your drivetrain, visit our component collection at Swinnerton Cycles to find an extensive selection of parts, brands and series to suit your bike, drivetrain and riding style.
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