Bike Gears Explained
On the surface, understanding your bike gears is pretty simple. You push the leaver one way to make it easier to pedal, and the other to go faster. Picking the right gears to install on your bike however can be much trickier.
Most of us just end up riding the gears that came with our bikes, but if you don’t think about swapping out for different scenarios, you might end up making things much more difficult than they need to be.
The gear ratios you want to use for a hilly cycling holiday in Mallorca are not the same as the gears you want for a time trial, criterium, club ride or city riding. Our complete guide to bike gears takes the mystery out, and will have you boring your friends to death talking about gear ratios in no time at all.
Front Gears (Chainrings/Crankset)
The front gears are referred to as chainrings. The whole assembly with the crank arms is called the “crankset” or sometimes “chainset”. Most crank sets have either two (called a double or 2x), or three (called a triple or 3x) chainrings. Single (or 1x) chainrings are gaining popularity, particularly among mountain bikers and cyclocross riders, but are still a fairly niche application. On the crankset, the smallest chainring is closest to the frame. The smaller the chainring, the easier the pedaling. As we move the chain away from the centerline of the bike, the pedaling gets harder but you go faster. Typically the chainrings are identified by mentioning their position (“inner”, “outer”, or, in the case of a triple “middle”), or by their size “big ring”, “little ring”. On a triple they’re usually called “outer/big”, “middle” and the smallest one has a special name – “granny gear” or just “granny”.
Rear Gears (Cassette)
The gears on the rear wheel are called “cogs”. They are assembled into a “cassette”. Most bikes built in the last few years have between 8 and 11 cogs in the cassette, but super-cheap department store bikes usually have 7. The largest cogs are closest to the wheel and the gears are numbered from the inside out. The larger the cog the “lower” the gear and the easier it will be to pedal, but the slower you will go.
How Many Gears?
When we talk about how many “speeds” a bike has, there can be some confusion. The marketing department likes to multiply the number of cogs by the number of chainrings because big numbers are impressive. But the fact is there’s actually a lot of overlap, so a 9×2 doesn’t really have 18 gears. People who actually ride bikes only refer to the number of cogs in the cassette, so an 8 speed, a 9 speed etc… They may also mention whether they have a single, double, triple crankset, or they may simply say “9×2” or “2×9”.
The chain gets moved from one cog to another or one chainring to another by means of a derailleur. The front derailleur is a fairly simple device that simply pushes the chain off of one chainring to be picked up by the next.
The rear derailleur is a little more complex as it has two jobs. Like the front, it guides the chain from one cog to the next, but it is also responsible for maintaining chain tension and taking up the slack when we move from bigger gears to smaller ones. The rear derailleur has two little gears (actually called pulleys) in it, and the chain makes an “S” turn through them. The upper pulley (closest to the cassette) is referred to as the “jockey pulley” and the lower pulley is called the “idler pulley”. The pulleys are held in position by the “cage”.
Derailleurs can only work on the side of the gears from which the chain is fed onto them while you’re pedaling. As a consequence, the front derailleur is on the tension side of the chain. This means that it is difficult to shift your front gears under load, so you should “lighten” your stroke a bit when switching chainrings. The rear derailleur is on the slack side, as a result, it can fairly effectively switch gears under load. It is important to note however, that in order to switch gears the chain must be moving forward, so don’t try and shift gear while coasting, back-pedaling or stopped.
With both the front and the rear derailleur, when the shift cable is pulled, it will move the chain to a larger gear. When the cable is released, it will move the chain to a smaller gear. Just remember that larger gears at the rear mean easier pedaling but more torque, and larger gears at the front mean harder pedaling but more speed. Going from “easier” gears to “harder” gears is called “upshifting”, and the reverse is called “downshifting”.
Teeth & Bike Gear Ratios Explained
11 cogs on the rear cassette and two on the front chainring essentially gives you 22 different options (though some of these may cross over so not strictly true). However the key element that will determine how hard you work is the difference in the number of teeth between the front and rear which will provide you with a gear ratio. Let’s take my bike as an example:
The chainring (front) on my bike is 50/34T. That means the outer ring has 50 teeth and the inner ring has 34 teeth.
The rear cassette is 11 speed 11-32. This means there are 11 cogs ranging from 11 teeth up to 32 teeth (the exact cogs are 11/12/13/14/16/18/20/22/25/28/32).
The combination of your selected chainring and cog determine the gear ratio. The gear ratio, combined with the circumference of your wheel and tyre determines how far you will travel with each revolution of the cranks.
The Hardest Gear
Let’s say I am in the hardest gear on each which means I would be riding on the 50 tooth ring on the front, and the 11 tooth ring on the back. To get our gear ratio we divide the number of teeth on the front by the number on the back:
50 ÷ 11 = 4.55
This is expressed as 4.55 : 1 meaning that for every 1 turn I make of the pedals at the front, I will turn the back wheel 4.55 times. This is the gear I would use on the flat. It is going to take quite a lot of effort to get it moving, but when I do I will move quickly.
The Easiest Gear
This would be the opposite end, the small ring on the from and the biggest on the back. The reason for this is that they are the closest together, meaning you get a really low ratio. On the bike I ride this is 34 teeth at the front and 32 at the back so really close.
34 ÷ 32 = 1.06
1.06 : 1 means I am only just moving the back wheel through more than one revolution for every turn of the crankset. This would be the gear I am using on the very toughest of climbs allowing mean to spin the wheels quickly to get my cadence high.
Different Gearing Set Ups
CRANK SET (FRONT GEARS)
You may sometimes hear cranksets referred to as ‘compact’ or ‘standard’. A compact crankset typically has a 50 tooth (50T) big ring and a 34 tooth (34T) little-ring. Standard cranksets are typically 53T/39T. In most cases, you can change your chainrings to have different tooth counts, but as a general rule you don’t want to have more than a 16-tooth difference between the big ring and little ring or you may have shifting issues. As for triples, they tend to run even smaller gears and more closely spaced 26T/36T/46T and 52T/42T/32T is a common triple crankset configuration. With 10 and 11 speed drivetrains becoming the norm, we’re seeing triples fall out of fashion and even single ring cranksets are becoming popular because of the wide range of ratios an 11-speed cassette can span.
What Can We Learn From This?
The key learning from all this information is to make a conscious choice when you purchase a bike as to the gear range that you want.
If you are climbing, then the natural choice is going to be a compact crankset, or in extreme cases a triple, but think about the rear cassette. My first bike had an 11-28, but I really like keeping a high cadence on the hills, so on my new bike I have opted for 11-32. This means I still have a nice fast high gear, but the lowest gear is significantly easier to pedal. If you are are Time Trialer then you may want to opt for a standard crankset as it will give you a higher top gear. This paired with something like an 11-23 rear cassette would be great for flat course as it would give you very small changes between the gears meaning you could keep the cadence exactly where you wanted it.
The key is to know the kind of riding you are planning to do with the bike you purchase and choose the gearing accordingly. I have produced the chart below to help you understand the typical ratios available. Remember the higher the ratio, the harder/quicker the gear is going to be.
How Do We Use Gears?
So now we know the all of the major parts of the drivetrain, their names, and a basic idea of how they function, but how do we use them? Like a car engine, the human body can only efficiently make power through a narrow RPM band. Our goal while cycling is to move as efficiently as possible, so we use different combinations of gears to keep our pedaling speed (cadence) within that efficient range, and to do so without pushing too hard on the pedals. For most people, the most efficient cadence is somewhere between 80 to 100 rpm. If you’re new to cycling, this may feel fast at first, but you can quickly adapt. Most of the time you want to be ‘spinning’ lightly within this RPM range and spreading your effort smoothly around the stroke. Beginner cyclists tend to ‘mash’ the pedals from about the 1 o’clock position through the 5 o’clock position. An experienced cyclist smoothly applies power from about the 12 o’clock position through the 7-8 o’clock position.
That’s the theory, now here’s the practice. First, you will choose the front chainring for the general terrain. Think of the chainrings as the “range selector”. Typically, you’ll use the outer chainring for descents, riding in the flats and for gentle climbs. When the climbing gets steeper, you can switch to the inner (or middle) chainring. On a triple, the innermost ‘granny’ gear is usually reserved for the most arduous of climbs. Once you’ve selected the appropriate chainring, you then use the rear gears to fine-tune your effort level and maintain your cadence. There are a few things to keep in mind however:
- Avoid ‘cross-chaining’: Cross-chaining is when you have a little/little or big/big combination. This puts stress on the drivetrain and can cause premature wear of the components. It’s OK if you occasionally find yourself cross-chained – say for a short, steep climb – but it is something you’ll generally want to avoid. The rule of thumb to follow is that when on the big ring, only use the smaller two-thirds of the cassette. When on the inner (or middle) ring, only use the inner two-thirds. When in ‘granny gear’ limit yourself to the largest two or three cogs.
- Anticipate your shifts: Keep an eye on the road ahead and shift before you have to shift. You’ll maintain a smoother power output, and you’ll be shifting at a time when there’s less stress on the drivetrain so your shifts will be smoother too. This also means that as you approach a red light or stop sign, you should downshift a couple of gears in anticipation of getting rolling again.
- Keep pedaling!: It is much more efficient to keep a constant, steady power rather than ‘burst and coast’ riding. It sure feels like you’re getting better exercise when you make that big effort, but you’re putting all the load on your muscular system, which isn’t really good at sustained effort. Spinning light and fast ends up putting out the same amount of power, but shifts the load to your cardio-vascular system, which is good at endurance activity.