A Guide to Bike Gears: Bike Gears Explained
Whether fixing, fine-tuning your gears, or building a bike from scratch, you must learn how bike gears work. This guide gives you everything you need to know about bike gears: how they work, how to use them efficiently, how to adjust and index them correctly and how to fix them if they are broken.
How do bike gears work
Bike gears are the mechanism on a bike that allows you to adjust the resistance while pedalling, making it easier or harder to pedal to help you cycle over various terrains and at different speeds.
Gear ratios
Firstly, to understand gears, you need to understand gear ratios. A gear operates on the principle of ratios. The ratio compares the number of teeth on the two bike gears and determines how many times one gear will turn relative to the other. For example, if you have a gear with 10 teeth and one with 20, the gear ratio is 1:2, meaning the smaller gear will turn twice every time the larger gear turns.
The components
Chainrings (front gears)
Bikes typically have two or three chainrings attached to the crankset (where the pedals are attached). The front derailleur controls and moves the bike chain between the chainrings and determines the size of the gear ratio when paired with the rear gears.
Cassette (rear gears)
The cassettes are the rear gears attached to the rear wheel hub. The rear derailleur controls and moves the chain between the cassette rear cogs. The size of the rear gear will affect the gear ratio.
Gear shifters
The gear shifters are the controls on the handlebars that allow you to change gear. There are two types of shifters on bikes: grip shifters, which twist to change gear, and trigger shifters, which you push or pull. Each shifter controls one derailleur.
The gear system
When you operate the gear using the shifters, the derailleurs move the chain to a different chainring and gear, altering the gear ratio. Moving to a harder gear, e.g. the largest chainring at the front or a smaller one on the back, will make it harder to pedal but allow you to travel faster. Conversely, moving to an easier gear, e.g. a smaller chainring or gear on the front or a larger one at the back, will make it easier to pedal but will reduce your speed.
By adjusting your gears, you can maintain an optimal pedalling cadence regardless of terrain and shifts in elevation, making your rides more efficient and comfortable.
How to use bike gears
There is a right way to use bike gears to maximise pedal cadence efficiency. Here are our top tips on how to use bike gears effectively.
- Start in a comfortable gear. When starting from a stop position, begin on a comfortable low gear. Typically, this means starting with a smaller chainring at the front and a larger chainring at the back, making it easier to pedal.
- Anticipate terain changes. Adjust your gears appropriately as you approach hills and descents or changing terrain. For example, shift to a lower gear (smaller chainring at the front or larger chainring at the back) before climbing a hill to maintain momentum and prevent straining your muscles.
- Maintain pedaling cadence. Aim to maintain a consistent pedalling cadence that you can pedal throughout your ride. A comfortable pedalling cadence is typically between 60 to 90 revolutions per minute (RPM). Shift your gears to maintain this cadence, adjusting to match terrain or wind resistance changes.
- Shift before you need to. You may find it easier and smoother to shift gears before you need to by anticipating the changes in terrain and gradient. Shift preemptively to maintain a smooth and efficient pedalling rhythm.
- Utilise the full range of gears. Experiment with different gear combinations to find the most comfortable and efficient setup for different riding conditions. Don’t be afraid to utilise all the gears, both front and back, to find the right balance between pedalling effort and speed.
- Avoid cross-chaining. Cross-chaining happens when you use extreme gear combinations, for example, the smallest chainring at the front and the smallest gear at the back or vice versa. Cross-chaining causes unnecessary wear on your drivetrain and may lead to poor shifting performance.
- Practice and experiment. Practice makes perfect when becoming proficient in using bike gears. Experiment with shifting gears during different rides and consider how the changes affect your speed and effort. After a time, changing gears will become second nature.
How to fix bike gears
If you have issues like your bike gears slipping or not shifting correctly, here is our step-by-step guide on diagnosing and fixing these common bike gear issues.
- Inspect the gear components. Before you do anything else, check for wear, tear and misalignment on your gear components, including the chain, cassette, chainrings, derailleurs, shifters, cables and housing.
- Check the derailleur alignment. Ensure the front and rear derailleurs are properly aligned with the gears, as misaligned derailleurs can cause poor shifting performance. Use a bike stand to hold the bike off the ground and shift through the gears to check the alignment of each one.
- Adjust the gear cable tension. If your gears are not shifting accurately or smoothly, there could be a cable tension issue. To amend, loosen the cable anchor bolt on the derailleur and adjust the tension using the barrel adjusters near the shifters. Retighten the cable anchor bolts and test your shifting performance.
- Adjust the limit screw. If your chain is shifting off gears or experiencing difficulty reaching certain gears, you may need to adjust the limit screws on the derailleurs. The limit screws control the maximum movement of the derailleurs and prevent the chain from shifting too far. Use a screwdriver to make small adjustments until your shifting is smooth and accurate.
- Inspect and lubricate components. Inspect the chain and chainrings for dirt, rust and debris. Clean the components using a degreaser and a brush, then lubricate the chain. Ensure all moving parts are lubricated to reduce friction and improve shifting performance.
- Replace worn components. If your gears are still skipping or shifting poorly despite being adjusted, inspect the chain, cassette, chainrings, and cables for signs of wear and replace any worn or damaged components.
- Test and fine-tune. After adjusting, conduct a test drive to see if the shifting issue is alleviated. Shift through all the gears under different conditions, uphill, downhill, and on flats, to ensure they shift smoothly and accurately.
- Consult a professional. Consult a bike mechanic if you are still struggling to diagnose and fix your shifting issue.
How to adjust bike gears
Whether you have an issue with your gears or you’re building a bike from scratch, you will need to index your gears. You must fine-tune the derailleur to adjust your bike gears to make shifting gears smoother and more precise. Adjusting bike gears, also called gear indexing, involves
- Checking the limit screw. The limit screw controls the maximum movement of the derailleurs and prevents the chain from shifting off the gears. Use a screwdriver to adjust the limit screw.
- Setting the cable tension. Shift the chain onto the smallest gear on the rear cassette and the smallest front chainring. Loosen the cable anchor bolt on the rear derailleur and pull the cable taut with your hand. Retighten the anchor bolt and shift through the gears to check shifting performance. If the shifting is still sluggish or hesitant, fine-tune the cable tension using the barrel adjuster near the shifter until the shifting is smooth and precise.
- Indexing bike gears. Indexing is the precise alignment of the derailleur with each gear on the cassette or chainring. Here’s how to index bike gears: adjust the indexing by altering the barrel adjuster on the derailleur. Shift through the gears while making small adjustments until the chain smoothly and accurately transitions between gears without skipping.
Bike gears at Swinnerton Cycles
Whether attempting to fix a misaligned bike gear or build a bike from scratch, knowing the ins and outs of bike gears is imperative. You should now know how to successfully fix and adjust new and broken bike gears to get the best gear-changing and cycling experience.
In most cases, you can fix and adjust gears on a bike and get them working again. However, if you need to replace any part of your gear mechanism because they are worn or broken, browse our components collection to find the part you need. If you are attempting a bike build project, we recommend purchasing a complete groupset so that you know all the parts will work perfectly in tandem.
Once your gears are fixed and functioning, practice makes perfect when changing gears. Enhance your cycle using the gear-changing tips above for a smooth ride and a consistent pedalling cadence, regardless of the terrain or gradient.