Introduction to Gears

As this is a non technical article, I will not use any technical jargon. For the sake of this article I will refer to a derailleur as a gear changer or changer. The mechanism which makes the gear changer move is the shifter. As there are many different sorts available, I will just call it a shifter.

So Many Gears!

So you are looking at a new bike which may be your first bike, and the Local Bike Shop (LBS) tells you it has 24 gears. Some trucks have that many gears, and your car only has five at the most. Why so many gears?

Firstly we need to look at a bicycle's chain on a common bike. If you look at where the chain goes around the pedals, these rings with teeth are referred to as the front chain rings. Oh yes, and these chain rings can bite your shins too!

Close up view showing chain rings and plate to stop the chain coming off.

Above is a typical view of a bike with three chain rings. There is a large cog, a middle sized cog and a tiny baby cog. The chain is currently on the middle cog. The other bit covering the chain to the left of the picture with the words "ALTUS" written on it is the gear changer.

Just for information, the red "V" is pointing to a plate, which is designed to stop the chain coming off and jamming between the chain ring and the frame. Some mountain bikes have these.

In the above picture, when you move the shifter on your handlebars, the gear changer moves across and pulls the chain onto a different chain ring. This is how the gears are changed. The above picture shows the chain rings that are attached to the pedals. The smallest chain ring is the lowest gear. The lowest gear is the easiest gear to pedal in, just like first gear in a car. You cant go very fast in this gear, but travel slowly and easily up steep hills.

The largest chain ring is used when traveling at a reasonable speed. So using the same system as a car, the smallest and easiest to pedal chain ring is first, the middle is second, and the biggest is third.

So using this system, you would start off riding from a stop in first gear, and as you build up speed you will shift to second and eventually third gear. Sounds easy doesn't it? It is in theory, but because you have to change gears while the pedals are turning, you have to remember to change back to first gear before stopping.

On most shifters, you will see a little indicator which tells you what gear you are in when riding. Seeing a 1 on the indicator means the chain is using the little chain ring, the 2 is on the middle, and the 3 means the chain is running on the biggest chain ring.

Now if this was all, this would make gears on a bicycle easy wouldn't it? You would start off riding from a complete stop in first gear and as you pick up speed you shift to second, and eventually third. As you come to a steep hill and find it hard to pedal, you change back a gear.

As the hill gets steeper, you may have change back to first, and if you cant pedal anymore, you will have to get off and walk. Before coming to a complete stop, you have to remember to change back to first gear, so that when you go to ride off, you are in the easiest gear. Some bicycles come with only two chain rings and the rare bicycle might have four.

If it was only this simple, but life was never meant to be simple. Somebody decided to add more gears, and these were added to the rear wheel. Actually gears started off on the rear wheel and somebody added more to the front, but for the sake of this article, I started with the chain rings, as it is easier to understand.

Now I'm Confused and 1 is not the Smallest!

Looking at where the chain goes around the rear wheel, you will see a cluster of cogs, with the smallest one being on the outer part of the cluster, and the largest being closest to the wheel's spokes.

A view of a rear cluster that has a 34T large cog.

The above photo shows a typical view of a rear gear cluster and gear changer. Now if you use your shifter to change to 1, which is the easiest gear, you will see that the chain is on the largest cog of the cluster. Confused? This is the exact opposite of the front chain rings. Remember that 1 on the chain rings is the smallest.

On the rear cluster, the largest cog is the easiest to pedal in. So let's forget about the front chain rings, and just concentrate on the rear cluster. The common amount of cogs on a rear cluster is eight, which is shown in the above picture. The biggest cog is the easiest to pedal in, and the smallest is the hardest.

The shifter on the handlebars may have an indicator, and 1 means the chain is on the biggest cog and 8 means the chain is on the smallest cog. So you would start off riding in first (biggest cog) and as you build up speed, you eventually shift through all eight gears to end up on the smallest cog.

As you come to a steep hill, you will change down from gear 8 to gear 7. This actually pulls the chain up the gear cluster. So you change down a gear, but the chain moves up. This is what confuses a lot of people. Unlike the front chain rings, you shift down a gear and the chain moves down a ring in size, the rear is the exact opposite.

As you climb steeper hills, you may eventually shift down through all the gear numbers and end up in gear 1 which means the chain is on the biggest cog. When you cant pedal anymore up that steep hill, you get off and walk. As these gears require the pedals to be turning to be able to change, you must also remember to change to the easiest gear before stopping.

In the above photograph, the chain is on the fifth cog down from the top which means it is in fifth gear. Gear 1 is the biggest cog and gear 8 is the smallest. That means there are three gears left for the chain to use as the bike goes faster. Some rear gear clusters may have as many as 10 gears or only five.

So I have 24 gears then?

If you add up the amount of rear gears and multiply by the amount of front chain rings you will find out how many gears the bike has. In this example we have three chain rings and eight cogs on the rear cluster giving a total of 24 gears. Technically this bike has 24 gears.

Notice how I said "technically". That's correct! While there are 24 possible combinations of different gears they are not all useable. Some of them are duplicated and these duplications allow the chain NOT to be used in extreme combinations.

Very few people get a manual with their bike, and of those that do, very few people even read it. Most manufacturers do not recommend using certain gears because of extreme sideways stress on the chain, hence the duplication of certain gears.

To give an example do not use the small chain ring (1) and the small rear cog (8) because the chain is running at an angle between the gears. This puts stress on some chains and can cause it to wear out quicker. You will usually find that this gear combination is duplicated by the middle chain ring (2) and one of the other cogs on the rear cluster. You may also find in the extreme combinations that the chain makes a noise because it is rubbing on the front changer.

The other extreme example is the large chain ring (3) and the largest cog on the rear cluster (1). Keeping in mind that the largest cog on the rear is easiest to pedal, we don't want to match it to a chain ring that is hard to pedal.

So to make is easy to remember, easy to easy and hard to hard. Easy on the front chain rings does not run too well when connected to hard on the rear. So easy to easy is safe to use and hard to hard is also safe to use.

Most of the unusable gear combinations are duplicated by some of the other combinations. I usually start off riding in my easiest gear, which is small chain ring (1) and largest cog on the rear (1). I then shift to 2 and then to 3 on the rear cluster.

Following that, as I pick up speed, I shift to the middle chain ring (2) and continue to shift the rear cluster down to gear 6, and if I am still riding faster, I shift to the largest chain ring (3) and shift the rear cluster through gears 7 and finally to gear 8 which is the smallest cog.

As I slow down I usually practice the above routine, but in reverse. This stops the chain from running at acute angles. It is perfectly fine to run all 8 rear gears when on the middle chain ring (2) if you wish.

How many gears do I have then?

Using my formula above, I have about 10 gears. 3 when using the small chain ring, 4 when using the middle chain ring, and 3 when using the largest chain ring. In real life, I usually ride around on the middle chain ring and use all of the rear gears. When I get a steep hill, I will use the small chain ring, or if I am traveling really fast, I may use the large chain ring.

Due to the fact that all of the cogs in the rear cluster and the chain rings can have their sizes changed it is quite easy to set a bike up to be able to use the system that I use. In fact that is how mine is set up, and most bikes will be set up this way.

As a beginner, the best way to get used to a gear system is to use the middle chain ring (2) and just use the rear 8 gears. One day you will find a steep hill, and remember that you still have the small chain ring. Due to the difference in sizes between the small and middle chain rings, shifting down to the smallest chain ring may cause your speed to drop off too fast.

Usually a drop to the small chain ring will mean shifting the rear gears up a number or two to get the next usable gear. The opposite will also apply when going faster and shifting to the large front chain ring.

That is why I use the above combination of gears. Sometimes depending on the terrain, I may not shift to the small chain ring but continue moving the rear gears to the bigger cogs. In the case of riding a loaded touring for example and I am coming to a steep hill, I may be in gear 6 on the rear and the middle chain ring (2) and may elect to shift to the small chain ring.

This will give me the easiest gears before I need them and I don't lose too much speed. That is the good thing about these gear systems as they are flexible and allow different use depending on the terrain. The same applies when going down a steep hill. I may be in gear 3 on the rear and the smallest chain ring, and shift directly to the large chain ring to take advantage of the steep down hill.

For those people who have driven trucks and buses, another analogy is to pretend that the rear gear cluster is the gearbox and the chain rings are a 3 speed differential. Another way of thinking is to think of the rear gears as the gears and the chain rings as easy, normal and hard to pedal.

You may wish to go on and read this article.