Bike Gears: How They Actually Work (From Someone Who Learned the Hard Way)

True story: I spent my first two years of cycling terrified of using my front derailleur. Just… never touched it. Thought I would break something. Rode around on whatever chainring I happened to be on when I bought the bike, grinding up hills in too hard a gear and spinning out on descents.

Looking back, that was incredibly dumb. But nobody actually explained gears to me in a way that made sense. So here is my attempt to do that for you.

The Basic Idea (No Engineering Degree Required)

Your bike has gears so you can match your effort to the terrain. That is literally it. Going uphill? Shift to an easier gear so you can actually turn the pedals without dying. Flying downhill? Shift to a harder gear so you are not spinning like a cartoon character.

The goal is to keep your legs spinning at a comfortable rate – most people are happiest somewhere around 80-100 revolutions per minute. Gears let you maintain that cadence whether you are climbing a mountain or cruising on flat ground.

What the Heck is a Drivetrain?

There are four main parts you need to know:

Chainrings (The Big Circles by Your Pedals)

Most road bikes have two of these – a big one and a small one. Mountain bikes usually have one these days. The bigger the ring, the harder it is to pedal (but you go farther with each pedal stroke).

Cassette (The Pyramid of Gears on Your Rear Wheel)

This is a stack of different-sized gears on your back wheel. Small cogs equals harder to pedal, big cogs equals easier to pedal. A typical road bike cassette might have 11 or 12 different cogs.

Derailleurs (The Mechanism That Moves Your Chain)

These are the little arms that push your chain from gear to gear. Front derailleur moves the chain between chainrings. Rear derailleur moves it between cassette cogs. They are controlled by…

Shifters (The Levers You Actually Touch)

On road bikes, these are usually integrated into your brake levers. Click one way for easier, click the other for harder. Mountain bikes and hybrids often have separate thumb shifters.

How to Actually Use Your Gears

Here is what took me way too long to figure out:

Small chainring plus big cog equals easiest gear. Use this for climbing. If you are not using this on steep hills, you are making life harder than it needs to be.

Big chainring plus small cog equals hardest gear. Use this for descending or going fast on flat ground. If you are spinning out (pedaling fast but not going anywhere), shift here.

Everything in between is for, well, everything in between.

The Thing Nobody Tells Beginners

You have two shifters, and they kind of overlap. Your small chainring with small cog is about the same difficulty as your big chainring with big cog. This means you can often achieve similar gearing with different combinations.

I ride in my small chainring way more than I thought I would. It is not just for steep hills – it is good for any relaxed riding where I do not need to be going fast. Save the big ring for when you are really working.

Cross-Chaining: The Thing to Actually Avoid

You know how I mentioned you can get similar gears with different combinations? Well, some combinations are BAD. Specifically:

• Big chainring plus biggest cog (your chain runs at a severe angle)
• Small chainring plus smallest cog (same problem, opposite direction)

This is called cross-chaining. It wears out your chain faster, can cause noise and rough shifting, and just feels weird. I did this for months before someone pointed it out. The grinding noise I was ignoring? Yeah, that was bad.

General rule: if your chain looks like it is running diagonally, shift to avoid it.

Electronic vs Mechanical Shifting

My first nice bike had mechanical shifting (cables running to the derailleurs). My current bike has electronic (Shimano Ultegra Di2). Both work fine, honestly.

Mechanical pros: Cheaper, easier to fix on the road, no batteries to charge. Cons: Cables stretch and need adjustment, shifting is not as precise.

Electronic pros: Buttery smooth shifts, never goes out of adjustment, can customize shift patterns with an app. Cons: Expensive, need to remember to charge it, if something breaks you are not fixing it roadside.

Electronic is nicer. Is it twice-the-price nicer? Debatable. My old mechanical bike shifted fine once I learned to keep it adjusted. But man, electronic shifting is pleasant.

Modern Drivetrains: 1x, 2x, and Why It Matters

Here is a trend that confused me initially: lots of bikes now come with just one chainring up front (called 1x or one-by). No front derailleur at all.

My gravel bike is 1x and I love it for that bike. One less thing to think about, no front shifting, simpler cockpit. The trade-off is you have slightly fewer gear options and bigger jumps between gears.

My road bike is 2x (two chainrings) and I prefer that for pure road riding. More gear range, smaller steps between gears, better for maintaining a precise cadence.

Neither is wrong – it depends on what you are doing and what you prefer. Do not let anyone gear-shame you.

Common Problems (And How to Fix Them)

Chain Skipping

If your chain jumps or skips when you are pedaling hard, something is worn out. Usually it is the chain, but if you let it go too long, you have worn out your cassette too (and maybe chainrings). This gets expensive fast. Replace your chain before it is too stretched and you will save money.

I have a chain checker tool that cost like $10. Use it monthly. When the chain is worn, swap it – takes five minutes. I have gotten way more life out of my cassettes since I started doing this.

Will Not Shift to Certain Gears

Usually a cable tension issue. The barrel adjusters on your shifters let you fine-tune this. Turn them a quarter turn at a time until shifts are crisp. If that does not work, the cable might be stretched or frayed – time for new cables.

Grinding or Rubbing Noise

Often cross-chaining (see above). Sometimes your front derailleur needs a tiny adjustment. Sometimes you just need to shift one more click to fully engage the gear. I still occasionally get this and just need to push the shifter a bit more firmly.

Stop Overthinking It

Honestly, gears are not that complicated once you use them for a while. The best advice I got was: just shift more. Shift early before the hill gets steep. Shift often to keep your cadence comfortable. You will not break anything by shifting (well, do not shift under heavy load, but light pedaling while shifting is fine).

I went from afraid to touch my gears to probably shifting too much. And you know what? My knees feel better, I am faster up hills, and I enjoy riding more. That is the whole point.