18 Speed Bike Gears Explained (Understanding Your Bicycle)

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Ben Jones

Cycling Basics, Other

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If you’ve got an 18-speed bike, or are thinking about getting one, then you might be wondering where those 18 gears are, what they do, and how you actually use them. We’re going to take a look at all this and add in a couple dos and don’ts when you’re riding a bicycle with 18 gears.

Why are 18-speed bike gears so confusing?

The more you delve into the world of bikes and cycling, the more you realize how confusing a world it really is.

And, in fact, gears are one of the most confusing parts of bikes.

Take an “18-speed bike” for example. Everyone knows what that means…yeah?

Well, actually, probably not.

First up, when you look at the bike, you won’t actually SEE eighteen gears.

Secondly, for each of those “18 speeds” you could pedal along at exactly the SAME speed.

And, once you’ve wrapped your head around that, how do you know WHEN or even HOW you should change gears?

What gear should you be in for downhills?

What gear should be in for uphills?

What gear should you be in for cruising along on the flat?

Once you’ve worked out what gear you should be in, how do you change from one gear to another?

To do that you need to use one of the two gear shifters.

On a mountain bike or hybrid bike, these are easy to track down (they are small levers next to the brake levers).

Road bikes gear shifters are a different matter though – on road bikes the gear shifters are integrated into the brake levers.

Sheesh!

So, bike gears can be tricky to understand and the goal of this article is to explain what 18-speed gears are.

We’ll also look at how to shift between those gears, some of the key jargon you need to know (e.g. “high gear”). We’ll look at some rules of thumb for what gear you should be in for uphills and downhills. Then, lastly, we’ll look at gear combinations that you need to avoid (think: “cross-chaining).

Ready? Let’s go.

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What does “18-speed” mean on a bike?

The first thing to notice about an “18-speed” bike is that you won’t actually be able to see eighteen separate gears.

Depending on the bike, the drivetrain* will either have:

  • 3 cogs (AKA “chain rings”) near the pedals and 6 cogs in the “cassette” at the rear wheel hub, or
  • 2 cogs near the pedals and 9 cogs in the rear wheel hub cassette

*The “drivetrain” is the collective term for all the components that make the wheels move round: the two pedals, crank arms, chain rings, cassette, the chain and front and rear derailleurs.

3 chain rings multiplied by 6 cogs in the cassette equals 18 gears (or “18 speeds”)
2 chain rings multiplied by 9 cogs in the cassette equals 18 gears

Here’s what this looks like when you’re crouched down next to the bike:

The main components of a bike drivetrain
These are the main components of a ‘drivetrain’

From the top down – see diagram below – you can see how each of these components fits together.

Using the front and rear derailleurs to shift the chain between different cogs combinations gives a different gear.

Birds' eye view of 2x9 gears
Birds' eye view of 3x6 gears
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How do you change gears on a 18-speed bike?

First (and most important) point: when you’re pedaling away on your bike there’s no rule that says you have to change from one gear to another.

The chain will wrap around one of the front cogs, take the power you generate at the pedals, and transfer it via one of the rear cogs to the back wheel. You can stay in that same gear throughout your bike ride, if you choose to.

That said, you will find that certain types of terrain make staying in the same gear all the time tricky. Going down steep hills, you might find your legs spinning too fast when you’re in too low a gear. Similarly, when you’re climbing up a hill, you might find your legs get achy and tired before you reach the top if you’re in too high a gear.

Ok, so no pressure, but sometimes change is good. Let’s look at how you do this and change gears.

Looking at the handlebars, you’ll see a pair of shifter levers that operate the gear changes by hand. The levers are connected to the derailleurs – this is a French word, meaning “de-rail”, and the job of the derailleurs is to nudge (or de-rail) the chain off one cog and on to the next one. On an 18-speed bike there are a pair of derailleurs, one at the crank by the pedals (the front derailleur) and one at the rear wheel hub (the rear derailleur).

  • The front derailleur is operated by the left gear shifter
  • The rear derailleur is operated by the right gear shifter

Modern bikes typically have one of a couple styles of gear shifter:

On most bikes (e.g. e-bikes, hybrid, mountain bikes and fitness bikes) the gear shifters are next to the brake levers. There are a pair on each end of the handlebars. For each pair, push one lever to change up and one to change a gear down.

Road bikes are somewhat different in that the shifters are integrated into the brake levers. There are variations between different manufacturers as to how these operate but, in general, the lever is pushed to one side to shift a gear, then a button on the brake lever is pressed to shift gear the other direction. This can be confusing when you look at a road bike for the first time and wonder where the shifters are!

When you’re changing gears, up or down, it’s essential to keep the pedals turning. The chain can only be nudged to a different gear when it is moving forwards along its path.

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Which gear on an 18-speed bike should you use for going uphill?

For easier hill climbing, change down to a ‘lower gear’.

The diagram below shows what a lower gear is on an 18-speed bike.

Lower gears on an 18 speed bike

Using the left shifter, move the chain to the smallest cog at the pedals. You will now be able to pedal uphill more easily as you will be in one of the lowest 6 gears on a 3×6 bike or the lowest 9 gears on a 2×9 bike.

Gear 1, the lowest gear, is where the chain runs between the smallest cog at the front and the biggest cog at the back. Use the right shifter to move the chain across to the biggest cog at the rear wheel and enjoy whizzing up hills!

Remember to only change gears one-by-one. Trying to jump up or down by multiple gears can lead to problems such as the chain getting stuck or falling off the cogs.

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Which gear should you use for flat or downhill on an 18-speed bike?

Once you’ve crested the summit of a hill, and are looking forward to the downhill, you need to adjust your gears to a more appropriate one.

Try to go downhill in a low gear and you’ll find that your legs are spinning without actually generating any push on the pedals – a waste of energy!

At this stage, you need to move up to a higher gear.

The higher gears on a 18-speed bike look like this (the highest gear combination is the largest chain ring at the crank and the smallest cog at the rear wheel cassette):

Higher gears on an 18 speed bike

To get into one of the higher gears, first use the left shifter to nudge the chain across to the largest chain ring (this is the one next to the right pedal).

Then, you’ll be in one of the 6 highest gears on a 3×6 bike or one of the 9 highest gears on a 2×9 bike. Use the right gear shifter to move between these gears – the highest gear for the steepest downhills is found by using the right shifter to move the chain to the smallest rear cog. This is known as your ‘top gear’.

It’s useful to plan ahead when it comes to gear changes – if you see a steep uphill coming up for example, then start changing down into a lower gear so that you’re ready for the climb.

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Beware of cross-chaining

Unfortunately, in practice, you won’t be able to use all 18 gears on an 18-speed bike.

Why? Well, there are two gear combinations where the chain is stretched diagonally and this can cause the chain to wear prematurely and can also give an irritating clicking noise as the chain tries to catch the spikes on the cogs.

The gears to avoid are:

  • Biggest front chain ring and biggest cog on the rear cassette
  • Smallest front chain ring and smallest cog on the rear cassette
Avoiding these 'cross chaining' gear combinations on an 18 speed bike

Thankfully, this still leaves another 16 gears to play with.

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Conclusion

Gears on bikes can be intimidating, especially when you have 18 combinations to choose from (and two that you should avoid!)

When in doubt, using the following handy rules:

  1. For easy uphill pedaling, use the smallest front chain ring (and for the easiest pedaling combine this with the biggest rear cog)
  2. For fast descents and on the flat, use the biggest front chain ring (for the fastest speeds combine this with the smallest rear cog)
  3. The front derailleur is operated by the left shifters
  4. The rear derailleur is operated by the right shifters

4 thoughts on “18 Speed Bike Gears Explained (Understanding Your Bicycle)”

  1. Great article! Thanks. My grandson’s new Dynacraft Gauntlet 18 speed (also from wal-mart) seems to want to “free-wheel” at random times. Eventually it will click back into gear. It has been doing this since relatively new, but we haven’t been able to trouble-shoot a solution. We are thinking the hub needs replaced?

    Reply
    • Hey Jim. Glad you liked the article.

      Yeah, that does sound like a problem with the rear wheel hub. Strange to see in a new bike, like your grandson’s though. I had the same issue on my mountain bike recently, but this had seen quite a bit of action by then! Might be worth taking it back in to Walmart.

      Cheers
      Ben

      Reply
  2. I went to the Internet to find out why the chain on my 14 year-old grandson’s new 18-speed Huffy was slipping off the chain ring and how to correct it. Too many variables. We’ll take it back to Walmart for the assembler to adjust it or to a bicycle shop. Since I was online, it was a perfect time to learn how to use 18 gears. Neither of us had the slightest idea. Does he really need 18 gears? No, but they’re cool. Your explanation of how the chain ring and rear cassette work together and how to use the 18 gears was easily understood. Well done.

    Reply
    • Hey Bill – I’m glad my article was useful! Sounds like your grandson’s bike might need some adjustment to the front derailleur – potentially a turn or two on the ‘H’ or ‘L’ limit screws on top of it. As it’s a new bike, then your best bet is to take it down to the store and get them to adjust it like you’re planning to do.

      Reply

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