Understanding the bike’s gears seems like a very difficult task at first. Trying to get my head around bike gearing first seemed so complex that I thought I would never understand it. I felt overwhelmed with the jargon: Gearset, Compact, Cassette, Derailleurs, and so on… In reality the essentials are very simple. Once you understand how the gears work and knowing how to use bike gears will keep your bicycle running happy for a long time.
When you cycle you are the engine and your bike’s gears transmit the force to the rear wheel, which propels you forward. Since your legs can only exert a certain amount of force and the terrain and the wind can vary it is through gearing that you can find the optimum ratio that will move you forward most efficiently.
Chances are that your commuter bike comes with front and rear gears as do most bicycles. The front gears are called chainrings the rear ones are called cassettes. Usually there are two or three chainrings on the crankset. The outer is the larger one with more teeth on it while the inner one is smaller one with less teeth on it and if it has a middle one that is the transitions between the two. The smaller the chainring the easier it is to pedal and the higher the torque (and lower the speed), the larger the chainring the harder it is to pedal and the higher the speed (and lower the torque).
The rear cassette is the exact opposite. The smaller cog is the hardest to pedal and is the lowest torque but it gives faster speeds in return, while the largest is the easiest to pedal, and gives slower speeds, but it gives the highest torque in return. All the gears in between are a transition from one extreme to the other.
The combination of the front and rear gears is what gives the gear ratio. This is the number that ultimately determines how easy or how difficult it is to pedal, and how fast your wheel will spin in return. The math is quite simple. If you are in your lowest gear at the front with 26 teeth and in the lowest gear at the rear with 26 teeth your gear ratio is 1 (26/26). This means that for every pedal revolution your wheel will rotate once. It is quite easy to pedal with this ratio and it is useful for climbing hills at low speeds. On the descent you will be in your highest gear, which may be 48 teeth on the front and 11 teeth on the cassette. This gives you a gear ratio of 4.36 (48/11). For every full rotation of the pedal your rear wheel will turn 4.36 times.
What do the numbers mean on my shifters?
Now that we’ve understood the basics, let’s move on to how the numbers relate to the cogs on your cassette and chainring.
The logic behind the numbers is that the smaller numbers refer to easier gears and the higher numbers refer to harder gears. If you observe your chain’s position during shifting you will see that at the front the higher the number the bigger the chain ring, while at the back the bigger the number the smaller the cog on the cassette. The achieved result is still the same: higher number = higher gear ratio = faster speeds = harder to pedal.
What’s the right gear for me?
There is no such thing as perfect gear. Certain gears or a range of gears can be comfortable for you on a certain type of road, which may be uncomfortable on a different type of road or for someone else on the same road. You can decide that based on your cadence and the effort you put in it. The exerted effort to a large extent will ultimately depend on factors such as terrain and wind.
Cadence: the key to moving efficiently
A normal range of cadence is between 60-100 RPM. Your effort to torque ratio is most efficient in this range. If you pedal too slow you will feel muscle fatigue, and if you pedal too fast then your heart rate will be too high. Neither of them is sustainable for too long.
Initially it is likely that you may find even 60 rpm somewhat challenging, but as you progressively gain more experience you can move into the 90-100 rpm range.
Also note that a lower cadence will allow you to keep your heart rate lower and therefore reduce body perspiration. If you want to read more about sweating and body odor, check out this other article on the site.
If you your rpm is outside the optimum range It is likely that if you are pedaling slower or faster than that then you can find a gear that is more comfortable for you, which brings back your cadence in that range of RPM.
How to shift without damaging my bike?
You’re probably familiar with the cracking sound if you’ve ever tried to change gears while climbing a hill or inadvertently changing gears before getting on your bike. Chances are that it wasn’t only loud, but it also took long for the chain to finally settle. You may also have heard some clicking sounds after shifting gears on your cassette following a steep uphill climb. These sounds are not only awful to hear, but they also puts stress on the components involved.
You should always keep the following rules in mind in order to maximize the life of your bike.
The first main rule is that you should not cross-chain, which means that the chain is on the opposite cogs on the chainring and the cassette. Instead of being in a straight or almost straight line, the chain is in an unnatural position. Cross-chaining can quickly wear out both the chain and the cogs involved, and because of the lateral tension and friction you also lose some of the power you put into pedalling (it may be barely noticeable, but every little helps).
Even though it’s not strictly speaking cross-chaining, it’s also best to use avoid using the lowest and highest cassette gear when the chain is on front the middle chain ring.
Since 3×8 speed bikes are quite popular, here is a little visual of what gears you should and shouldn’t use.
You can end up with a cross chain after a steep hill that you climb in your smallest gear. As you reach the top and start changing gears it is good to keep in mind to change gears both at the front and on the rear.
Remember that since we’re talking about gear ratios which is the result of two numbers, you can achieve similar or identical ratios without cross chaining.
No load bearing shift
Changing gear while putting a lot of force through the pedals pressure is called load bearing shift or load shift. It happens during acceleration and/or going uphills. You should always change gear under some load, but you should avoid doing it under excessive load.
Load bearing shift will result in loud cracks, delayed and imprecise shifting and it is very bad for the chain, cassette and chainring. In extreme cases you can chip a tooth on one of your cogs or even break your chain.
If you are about to hit a steeper part that you need to switch gears for, you should do so before reaching the steep part so you can do it without too much tension going through your chain. You will arrive at the difficult part in a higher cadence and climbing will be much easier.
You can use two tricks if you forgot to change gears in time on a hill:
- Try to gain a little bit of momentum with a few pedal strokes and then you can putting less effort change gears.
- If the road is wide enough and there’s no traffic, you can go in zig-zag or even turn around for just a short distance. This will allow you to take the load off the pedal so you can shift.
- If all else fails, you can get off your bike and lifting the rear wheel you can change gear. Once in the proper gear, mount your bike again.